RPM Threshold barrel twist/velocity chart

[Larry Gibson]

RPM threshold twist/velocity chart

I’m posting this at request for an easy reference to see the velocity range where the RPM threshold will most likely be found based on the twist of the barrel.

The RPM threshold is that point where accuracy begins to deteriorate when the RPM is sufficient to act on imbalances in the bullet in flight to the extent the bullet begins a helical arc in flight or it’s flight path goes off on a tangent. It is best noted when working up a load as velocity increases flyers begin to happen. Then as velocity is further increased the total group size increases sometimes to the point some bullets fly so far off they miss the target. A further indication the cast bullets at or over the RPM threshold is (or some of them in a load that is on the edge of the RPM threshold) the non linear dispersion of the group size as range increases.

Let us keep in mind the RPM threshold most often falls in the 120,000 to 140,000 RPM range with regular lube groove cast bullets. Exactly where the RPM threshold will be in fps depends on numerous factors; alloy, bullet design, fit, sizing, lube, GC’d and seated square, powder burning rate and the length of the barrel, etc. The RPM threshold may be lower than 120,000 RPM by careless casting and loading techniques or when using very soft alloys with very fast burning powders. Conversely, the RPM threshold can be above 140,000 by careful casting and bullet selection and preparation along with careful accuracy enhancing loading techniques, especially those for cast bullets at high velocity such as using slow burning powders that ignite easily and burn efficiently at lower pressures. The trick is to get the cast bullet to exit the muzzle as balanced as possible with as little deformation to it during accelleration. The more balanced the bullet is and the closer the axis of rotation coincides with the center of mass on exit from the muzzle and during flight the more accurate the bullet will be and thus, the higher the RPM threshold will be.

The RPM threshold is not a set “limit” of RPM or velocity. Best accuracy will be just under the RPM threshold or lower. Useable accuracy can be had above the RPM threshold if the ranges are not long and the accuracy requirement is not small. Keeping .223 cast bullets on a silhouette target out to 200 yards for example or keeping hunting cast bullet accuracy at say 4 moa if the max range to be used is 50 – 100 yards.
Again; the RPM threshold will generally be found between 120,000 to 140,000 RPM with regular commercial cast bullet designs and loading techniques most cast bullet shooters use.

In the chart below I’ve computed the fps for various common barrel twists for 120,000 and 140,000 RPM. For other twists in between anyone shouldn’t find it too difficult to interpolate. These fps figures should give you an idea in what fps range your loads, as you work them up, will probably bump into the RPM threshold and when accuracy will probably begin to deteriorate. Some pundates will crticise this chart saying they, or someone else, gets accuracy above the figures in the chart. For those who understand how to push the RPM threshold up with higher velocity cast bullet loads that can indeed be the case. However, as mentioned, the chart is for the majority of cast bullet shooters who do not care to push the RPM threshold up but simply want to understand where and why accuracy will probably deteriorate with their regular cast bullet loads. This chart was done for them.

RPM……….120,000……….140,000

Twist……….FPS…………..FPS

7”…………1166…………..1361

8”………….1333…………..1555

9”………….1500…………..1750

10”………...1666…………..1944

11”………...1833…………..2139

12”…………2000………….2333

14”…………2333………….2722

16”…………2666………….3111

18”………….3000…………3500

Larry Gibson

[Larry Gibson]

Here the 2nd chapter which was posted on 5 April 2008.I just changed a few remarks at the endhaving completed other tests in the last 5+ years.The proof of the RPM Thresholds existence isthere.If you have questions please readthe original thread ; http://castboolits.gunloads.com/showthread.php?28807-RPM-Test-a-tale-of-three-twists-Chapter-2/page2 (http://castboolits.gunloads.com/showthread.php?28807-RPM-Test-a-tale-of-three-twists-Chapter-2/page2)

Many good questions were asked and answered.The usual arguments are there also.There is no need to rehash those on thisthread because the proof is here.Icompleted a couple more tests and did not post the results because they confirmed what is here. My testing and load development then took the turn to see just how fast I could push a regular cast bullet of a ternary alloy with the 14” twist Palma rifle and maintainaccuracy of 2 moa or less and maintaining linear group dispersion out to aminimum of 300 yards.

I have succeededwith that and you have all seen the results of the 311466 cast of #2 alloypushed to 2600+ fps.I can harden thebullet with CU and push to close to 2680 fps.I can also go to a slightly lighter weight 311465 and push 2700+fps.That is about the limit with thecase capacity of the .308W.Yes I can usea faster burning powder and increase velocity but accuracy goes as the psi(measured with the Oehler M43 in that Palma rifle) climbs above 42,000psi.It appears that psi may be a “limiting”factor as that may be causing “plasticization of the bullet. I don’t know that for sure yet but the quickertime/pressure curve definitely damages the bullet more and lowers the RPMThreshold so accuracy does not hold to 2600 fps with the 311466.

My next step in this high velocity quest with accuracy isthree fold; 1st is to use a slower twist of 16”, 2nd isto use a longer barrel of 30” and 3rd is to use a case with largercapacity.The case for that needs tohold RL19, AA4350, H4831SC or RL22 right at 100% load density while keeping the311466 at or under 40,000 psi to achieve a velocity of 2700 upwards of 2900+fps.That would still keep the bulletbelow the RPM Threshold and the plasticization psi level. Additionally the case should have the longerneck of the 30-30 or ’06 in lieu of the shorter .308W case neck.This will keep a properly designed castbullet with the GC at the bottom of the case neck and the ogive just on the leadewith a short nose. The 2 current .30cal cast bullet designs available that fit this criteria are the Lyman/Loverin 311466and the LBT 311-160 cast bullet designs.Both also have 65%+ bearing surface.

The cartridge for the next step is the 30x57/30 XCB whichis basically a short chambered 30-06 with a tight neck.This cartridge was designed with these goalsin mind.If the case capacity is notenough it can be increased by simply rechambering with the same reamer a bitdeeper in increments until case capacity matches the desired goal of velocityand psi at 100% load density.Cases areeasily formed and shortened standard ’06 dies are used for forming cases andfor loading.I am in the process oflocating a quality barrel of correct length and dimensions to continue thequest.

As you all know in the past any time the RPM Threshold ismentioned the pundits come out in force to discredit me, let me say that again….todiscredit me.The existence of the RPMThreshold is proven.For those who can’tget their heads around it simple study it and perform a few testsyourself.You will find the RPMthreshold.For those who still don’tunderstand it is not a “limit” then I suggest you read the sticky on the RPMThreshold as I define it there.It isnot hard to understand.For those whowish to argue using the same old non proven arguments you’ve used for years withme in a further attempt to discredit me then please don’t waste your time orours.I will not respond.What would be more beneficial and appreciatedwould be for you to conduct your own thorough test and post the results.However, should anyone have an honestquestion pertaining to these test results I will entertain that.

Larry Gibson


RPMTest; atale with three twists

Chapter 2; Test 1 [311291 of 2/1alloy]

Yesterday broke clear with the promise of some warmth and little wind so Ipacked up the three rifles, the M43 PBL, the test ammoand the usual other necessary accoutrements for the range and set off theTacoma Rifle and Revolver Club to conduct the first test. Theprimary goal of this test was to see if we coulddetermine what causes the 311291 cast bullet to loose accuracy at a certainlevel. On arrival at TRRC I proceeded to set up. The benches there are verysolid benchrest designed and made. It was about 46-48 degrees in the shade ofthe firing line but was into the 50s in the sunshine. Wind was coming out of 11o’clock at 1-3 mph. The target distance was 103 yards. The testing was begunusing the 10” twist rifle and then the 12” twist rifle and finally the 14”twist rifle. The barrels were cleaned between every two 5 shot groups with 2foulers fired before testing was resumed. All data was collected via the M43using pressure recording, muzzle screens and down range screens. Besidesinformation on the rifle, load and testconditions the M43 provided data on the following information;

Data recorded for each shot;
• Velocity at the muzzle screens
• Proof variance of muzzle screens
• Time Of Flight between muzzle screens and down range screens (in front of 100yard target)
• The down range velocity
• Proof variance of down range screens
• Ballistic Coefficient
• Peak average pressure (psi.m43)
• Area under the pressure curve
• Rise of pressure curve
• Actual pressure curve

Summary of shot data for recorded shots in the group;
• Average velocity at muzzle screens
• Average Proof variance of muzzle screens
• Average TOF
• Average down range velocity at down range screens
• Average proof variance of down range screens
• Average Ballistic Coefficient
• Average peak pressure
• Average area under the pressure curve
• Average rise of pressure curve
• Standard Deviation of each of the above data averages
• The high reading of each of the above data fields
• The low reading of each of the above data fields
• The Extreme Spread of each of the above data fields.

The M43 also provided the additional data on Standard Atmospheric Ballistics;
• Bullet path from muzzle to 250 yards based on data entered and the actual BC
• 10 mph wind deflection
• Computed muzzle velocity (fps)
• Energy (ft-lbs)
• Power factor
• Recoil of the rifle
108092


The testing was uneventful except for one low shot that hit one of the downrange screens….ooops! It knocked a chunk of the plastic off but didn’t actuallyhurt anything. As the groups enlarged I did have a few rounds that hit on theedge of the window and didn’t read. This cut some of the group data to 4 shotsinstead of 5 and one group to 3 shots of recorded data. The first test waswith the 311291 cast of 2 parts WW to 1 part linotype. This gives an alloy thatwith the bullets air cooled the hardness of the bullets is similar to Lyman’s#2 alloy. That has long been a standard for cast bullets. As mentioned inChapter 1, the cases for all three rifles were fire formed to the specificrifles and “match prepped” as such. The primers used are WLRs. Two powders wereused. H4895, a medium burning powder, was used with a Dacron filler in 2 grincrements from 26 gr to 38 gr. This was expected, and did, to give velocitiesfrom 1700 fps or so up through 2500 fps. The second powder tested was H4831SC,a slow burning powder, loaded in 2 gr increments from 40 to 46 gr to give from90 to 100% loading density. The only sorting done with the 311291 bullets wereto inspect them for wrinkles, voids of non fillout. None were weighed forsegregation by weight. The gas checks used were Hornady’s. They were pre-seatedwith the Lyman GC seater on a Lyman 450 with the .311 H die and then lubed inthe .310 H die. The lube used was Javelina. At no time during the test wasthere any indication of leading or “lube failure”.

All told in Test 1 I fired 75 shots forrecord plus 10 foulers through each rifle for a total of 250 shots . Afterreturning home it seemed a daunting task to sort through the data, measuregroups and put it into some format that is easily presented on this forum. Icould list all sorts of numbers in various manners but that would just getconfusing. From the listed data the M43 provides on each shot plus the averageslet me tell you I’ve got lots of numbers! I decided instead to put thepertinent data onto graph form. That is a “visual” way to present informationand it gives valid comparisons which are easy to see and make comparisons from.It is easy enough to pull additional information of the graphs if you want it.However the little squares of the graph did not scan well so if you want somespecific information don’t hesitate to ask. I couldn’t get the graph on thiscomputer to work right so I resorted to graph paper and hand plotted them.

Without further ado we might as well get to the meat and potatoes of the test.Graph #1 is a comparison of velocity and pressure. There was considerableconsternation from some forum members that pressures would not be “exact”between the rifles. I stated that, disregarding the fact that there is alwaysvariation of pressures, even with the same load in the same rifle; thepressures need not be the same in each rifle. In fact they were not. When wegraph out the velocity/pressure of the same increasing loads out of differentrifles what we expect to see is a linear relationship between them. The linearlines for each (red = 10” twist, blue = 12” twist, green = 14” twist) shouldrun fairly parallel. This gives us a valid comparison of the time pressurecurves of each rifle with the other rifles time pressure curves. That’s exactlywhat we see in graph #1. As the pressure increases the velocity increasespretty close for the 10 and 12” twist rifles but the 14” had some problems. Wealso see a slight divergence as velocity increases. This is expected as the 12and 14” twist barrels were longer than the 10” twist barrel so velocityincreased more as pressure was increased. Thus the comparison between therifles is valid as the linear progressions are close to the same. Were one ofthem radically different then it would be obvious a comparison wasn’t valid.However there is a slight anomaly with the 14” twist. We could pontificate asto why and probably come up with numerous reasons, most of which would probablybe wrong. So let’s what the data can tell us regarding that anomaly.

108090

[Larry Gibson]

The answer to the velocity/pressure anomaly with the 14” twistis rather simple and is demonstrated in graph #2. The relationship betweenpressure and velocity is encompassed in internal ballistics so we merely needto look at that data showing the consistency of the loads, i.e. how consistentthe powder burns. Consistency of a load (given a teststring of several shots) is most often expressed in Extreme Spread of velocityand Standard Deviation of the combined averages of velocity. SD tells us what aload may do but ES tells us what that load did do. Since I am interested inwhat the load did do I compared the ES consistency of the loads with thepressure. In graph #2 the loads of the 10 and 12" twists all had ESs of 50fps or less. That is pretty good consistency given the spread of the loadsvelocities of 1700 fps through 2500 fps. The 14” twist had some early problemswith the powder burning efficiently. We see the ES for the 2nd and 3rd test loadswas considerably higher than the same loads in the 10 and 12” twists. Thataccounts for the small anomaly in the pressure curve of the 14” twist on graph#1. The other, and perhaps more important, piece of information graph #1 givesus is the time pressure curve of the same loads in the different twists. Obviouslythe curves are pretty close together and linear. Thus the time pressure curveor acceleration is very close to the same for each rifle.
108101





Next let us consider the question; if the time pressure curvesare the same then any deformation to the bullet due to acceleration will beclose to the same. Thus if the deformation to each bullet is the same at thesame rate of acceleration then any change to the form of the bullet will resultin a change to the Ballistic Coefficient. Following that then won’t any changesto the BC be the same for each twist since any deformation of the bullet shouldbe the same? To find the answer to that question we merely compare the BCs ofthe 3 different twists as the velocity increases (hence the accelerationincreases and deformation of the bullet increases). Graph #3 provides thecomparison of the BCs vs the velocities of each load in each twist. Let usremember that the BC in this case is a measured BC from the actual flight ofthe bullets not a guestimated one from some chart. These actual BCs measuredthe bullets ability to fly through the air efficiently. The higher the BC theless deformed and more stabilized the bullet was. It is readily apparent thatthe BCs stayed pretty much the same for all three twists during acceleration atall velocities and pressures. It is interesting to note that the BCs of thebullets from the 10” twist retained the highest BC at the highest velocity(acceleration). This is just the opposite what it would be as believed by someon this forum. The BCs from the bullets from all three twists stayed very closetogether and linear across the wide spectrum of velocity (acceleration) from1700 to 2500 fps which obviously shows the acceleration remained constantregardless of the twist of the barrel.

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So this is what we now know now about the same loads in the 3different twists; the time pressure curve is very close to the same, theacceleration is very close to the same and the BCs remain very close to thesame.



Let’s now take a look at the results on target. After all whatwe are looking at in conducting this test isthe accuracy at higher velocity and why that accuracy goes bad. Graph #4 showsus the group sizes vs pressure. Whoa there! Something is amiss….if the timepressure curves are the same, the acceleration the same and the BCs are thesame; then if the groups get larger as we increase velocity shouldn’t thegroups get larger by proportionally the same amount? [Note; by “proportionalamount” is an amount to compare the accuracy of each twist to each other. Theproportional amount factor of increase is found by dividing the increased groupsize by the smallest group with each rifle.] However, what we see is that thegroups do not get proportionally larger as velocity increases. The inaccuracyof the 10” twist increases by a factor of 5.38 while the inaccuracy of the 12”twist increases by a factor of 3.14 and 14” twist increases by a factor of 2.08.

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Hmmmmmm……pressure curve is the same, deformation of the bulletfrom acceleration is the same so then why doesn’t inaccuracy increase the same?Especially since graph #4 shows the group size vs pressure. But wait…there’smore (sorry, just couldn’t resist!). Doesn’t every one say that it is pressurethat destroys accuracy? We do see that accuracy with all three twists isdecreasing with the increase of pressure. If pressure was the only reason forthe decrease in inaccuracy then the inaccuracy should be proportional and wefind it isn’t. We also see a much greater increase of inaccuracy with the 10”twist than either the 12 or 14” twists. We also see the 12” twist’s inaccuracyto increase more rapidly than the 14”s inaccuracy. Again, if it was pressurethat increased the inaccuracy then why doesn’t the inaccuracy of all threetwists increase equally as the pressure increases? It seems there is somethingother than pressure adversely affecting accuracy and to a much greater extent.



Okay, let’s look at it one more way just to be fair. Graph #5 compares accuracyto velocity. Something wrong here again….that dreadful 10” twist is once againbeing more inaccurate by a greater proportional amount than either the 12 or14” twists. How can this be? We know the acceleration is the same; the BCs arethe same so the deformation of the bullet is the same yet the 10” twistsinaccuracy is disproportional to the 12 and 14” twists. It should be the sameamount of inaccuracy for each twist if pressure was the problem, right? Thelines for each twist should be linear right? Yet the proportion of inaccuracy isnot the same between the twists nor are the lines linear. Have we missedsomething? Is there another game afoot? We’ve a good handle on the internalballistics. We know about the terminal ballistics as the group sizes are selfrevealing. But have we really looked hard at the external ballistics (thebullets flight)? We know the bullets are stable, we know the BCs are gettingsmaller as the velocity increases telling us there is some deformation from theacceleration. We know the 10” twist had the highest BC at the highest pressureand velocity so why isn’t it as accurate as the 12 and 14” twists?

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Let us look at graph #6. It is a comparison of group sizes vs RPM. Notethe very, very obvious adverse affect that the increasing RPM hason the accuracy of the 10” twist. That red line really climbs up there! Alsonote that area of RPM where the majority ofaccurate groups fall; it is in or below the RPMthreshold. Also note that in or at the top end of the RPMthreshold is where accuracy begins to deteriorate.

108105



The tests with H4831SC seemed to be headed the same way but were inconclusiveas top velocity was only 2287 fps with 100% loading density. The 10” twistvelocity was 1928 fps through 2287 fps with groups running from 2.4” to 3.3”. RPM was138,900 to 164,700. Conversely the 14” twist went from 1906 fps to 2265 fps.Groups ran .95” to 2.2”. RPM was98,000 to 116,600. The highest peak pressure was 39,600 psi.M43. Thus Icouldn’t get into a high enough pressure/RPM range with all three twists tomake any comparison.

I am not going to conclude that there is an RPMthreshold as the test is not complete. Ishall wait until I conclude the testbefore giving a firm conclusion. However, we see from the test so far that veryfirm evidence is being found to make a definite case that the RPM threshold isalive, well and readily producible.

Note; a change of the testing direction was done after the original thread wasposted. I switched from the 311291 (177gr) to the 311466 (155 – 160 gr). Thereason for the change was to increase velocity with a change to slower burningpowders and to use a bullet with a design more conducive to HV accuracy.

Larry Gibson

[cainttype]

Thanks for your time, effort, and generosity in sharing your current results, Larry. I'll be interested in the rest of your test results when they're available.

[swheeler]

Waiting to see what you can do with 1:16 twist 30x57, thanks!

[waksupi]

Thanks Larry!

[Ford SD]

Thanks Larry
thanks very much for all the information --lots to think about
Book marked for future ref

I can see from your graphs where the Nodes are velocity ver group size
where the therotical velocity range will give you the therotical smallest group size
if you leave the nodes (or velocity range) group size increases for a small chance in velocity you get a big change in group size

Keep up the trigger time and keep sharing the information you find doing it

thanks Again[smilie=s:

[35 shooter]

Thanks so much for the effort your obviously putting into these tests and for sharing the info.I think that's the first time i've ever seen a ballistics lab set up at the range before.
The graphs are very telling. I'll be watching this with great interest all the way to the end results. The big surprise to me so far was that the 10 twist didn't hold a bit closer to the 12 twist. I mean i expected those results somewhat, but when it went south it went in a hurry. I just expected it to be a "bit" more proportional...wow!

[Driver man]

There are a lot of reasons why I love this site. the hours of reading and the vast experience of the members who share with us their trials and tribulations but most of all its articles like Larry has written here and who despite all the mud being flung by others still manages to produce these absolute gems for our edification and pleasure. Thank you Larry , I for one appreciate your informative and well reasoned articles. Now to try and improve my groups .

[44man]

Good job Larry, glad to see results. You have brought up another point to think about. Something that would be of great interest. We see what over spin is doing, what if the tests were repeated at long range, 300 or farther, to see if accuracy with each twist changes and at what point a boolit might go to sleep.
You would not need the instrumentation since you have the info, just shoot groups with each load.
I would like to know if the 1 in 10 twist will start to shoot a better group somewhere and if the slow twists will increase. Make another nice graph.

[Pilgrim]

44man - As I've noted in earlier posts, the Hunter Benchrest folks have gone to progressively slower twists. While I was shooting the winners went from 15" to 16" to 17" twists in .30 cal. rifles, 130 to 135 gr. bullets. Those folks shoot out to 300 yards in competition, with group sizes (100 yards) of .1" or less (5 shot) for the competitive shooters. The accuracy holds to at least 300 yards. Based on the Greenhill formula, bullets of 180 gr. would not stabilize in the super slow twists, but those lighter bullets sure enuf do. It has been noted also that linear velocity decreases rapidly while spin velocity decreases very slowly. Larry's tests don't change the fact that a stable bullet pretty much stays stable until it is stopped by something. On the other hand, his data clearly shows that you can "overspin" a bullet. In the case of lead boolits, overspin apparently can and does result in boolit deformation. The metal simply isn't strong enuf to withstand the centrifugal forces beyond a given rpm threshold. It would be curious to see what quenching does to the rpm threshold. Quenching allows higher pressures without boolit deformation/skidding/"whatever" occuring, but does it significantly alter the rpm threshold ? I don't recall any discussion of this, but suspect it would alter the rpm threshold. Whatcha think, Larry ? Pilgrim

[runfiverun]

looks like your 12" twist rifle is a very accurate one....

[dondiego]

Thanks Larry! I think............what did you say?

[Echo]

Outstanding, Larry. I'm copying for reference...

[offshore44]

Good show Larry. Thanks for the effort and time this took.

[fastfire]

Thank you Larry for all the time you put into this, very informative and keep it up.

[s mac]

I add my thanks also Larry. Always look forward to your post's.

[Larry Gibson]

Goodjob Larry, glad to see results. You have brought up another point to thinkabout. Something that would be of great interest. We see what over spin isdoing, what if the tests were repeated at long range, 300 or farther, to see ifaccuracy with each twist changes and at what point a boolit might go to sleep.
You would not need the instrumentation since you have the info, just shootgroups with each load.
I would like to know if the 1 in 10 twist will start to shoot a better group somewhereand if the slow twists will increase. Make another nice graph.

No need to "make another graph".....I'll show you the targets. In the past we have discussed the difference between the bullet "going tosleep" and "crossing the RPM threshold". The going to sleep has to do with bullet stability in flight on exit from the muzzle; basically when yaw and pitch settle down. Most often it is conceded that bullets go to sleep at a relatively short range; usually prior to 100 yards. However, some do believe bullets "go to sleep" at longer ranges. While I have never seen this either by shooting smaller groups of a sufficient sample at longer range or by watching bullet traces over manyyears of High Power shooting and long range target interdiction at 200 - 1000+ yards I do ask those who believe to show me. None have been able to produce an example on demand. None the less let us discuss it.

Additionally in our previous discussions we have noted that a bullet crossing the RPM Threshold has nothing to do with stability of the bullet either initially on muzzle exit or after it has crossed the RPM Threshold. The non linear expansion of group size as the range increases is another measure the bullet/load has crossed the RPM threshold. The non linear expansion may not be much or it may be a lot as it depends on the imbalance and the amount of centrifugal force (amount of RPM) there is to act upon it. Obviously non linear expansion of group size as range increases is counter to the "bullet going to sleep" theory.

Let me show you an example. We have the target results of 2 separate loads shown below using the 311291pushed by 4895 out of the .308W test rifle with the 10" twistbarrel. Ten shot test groups were fired at 50 yards, 100 yards and 200yards with each test load.

The 1st groups are with 28 gr of 4895 at a velocity of 1912 fps (muzzle velocity)at 137,664 RPM which is just under the upper end of the RPM Threshold. Note the 50 yard group minus the 4 foulers has 9 shots in .7” (I called the flyer down and away). The 100 yard group of 1.55” is of linear expansion to the 50 yard group (should be close to twice as big). The 200 yard group also is very close to linear expansion when compared to the 50 and 100 yard groups. Thus we see that even though this load is close to the upper end of the RPM Threshold the group expansion is linear. Also note all the bullet holes are round indicating excellent stability, even at 50 yards.

108122


The next groups are with a load of 38 gr of 4895 under the same 311291. The velocity is 2515 fps with 181,080 RPM which is obviously above the RPM threshold. If the cast bullets were going to “strip/skid” on the lands or go unstable it probably would have shown with this load. Obviously from the deteriorated accuracy we can conclude there was some damage to the bullet during acceleration. The measured psi was 51,700 btw. As we see there appears to be linear dispersion of the groups between 50 and 100yards. This is why 50 yard testing can be deceiving and perhaps we could erroneously conclude the bullets were “going to sleep” between 50 and 100 yards(?). However, when we shoot a test string at 200 yards we definitely see the non linear expansion between the 100 yard 4.7” group and 200 yard 14.5” group. We may also have erroneously concluded that the 4.7” 100 yard group was “good enough” and perhaps then expect to hit the heart lung area of a deer out to 200yards(?). Actual testing shows the group size was 14.5” (much larger than the heart/lung area) and was really pretty poor accuracy. Also note that all10 holes in the 200 yard target are round indicating no hint of instability ofthe bullets even though the are obviously no longer following the line offlight but are going off on a tangent orinto a slow increasing in diameter helical arc around the line of flight. Looking at that 200 yard target do we really think the bullets will "go to sleep" at a farther range and be more accurate?

108123108124


Larry Gibson

[Larry Gibson]

................ It would be curious to see what quenching does to the rpm threshold. Quenching allows higher pressures without boolit deformation/skidding/"whatever" occuring, but does it significantly alter the rpm threshold ? I don't recall any discussion of this, but suspect it would alter the rpm threshold. Whatcha think, Larry ? Pilgrim

Ah, Pilgrim......hardening the bullets is one way we can push the RPM threshold upwards and maintain accuracy. The hardening (WQing in this case) while perhaps preventing or attenuating the skid/stripping it also allows the bullet to withstand a higher rate of acceleration before unwanted obturation, sloughing or collapsing of the bullet occurs. Using longer barrels and slower powders also helps push the RPM Threshold up as does using a properly designed bullet.

Of course if building/rebarreling a rifle for cast bullet use is an option then using the slower twist makes it all so much easier to shoot our ternary alloyed cast bullets at high velocity and maintain accuracy.

Larry Gibson

[Larry Gibson]

looks like your 12" twist rifle is a very accurate one....

That it is and a prized possession of mine. I have cleaned the 1000 yard line with it a couple times and won a state championship with it using Redfield Palma sights on it. It is a M70 with a 26" Schneider barrel. Picture shows it with a Redfield 4x12 Ultra on it. I'm going to blubber like a baby when I shoot that barrel out...........

Larry Gibson

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[DR Owl Creek]

Larry,

Thank you for all your work, and for putting all that info out there for the rest of us. I've read the first two parts over twice, and studied the graphs. Its going to take a while just to digest that part. Please keep the info coming. Its really interesting!

Thanks again,

Dave

[44man]

Can't argue larry, there sure must be a difference in in what cast can take. I admit my work was with jacketed in varmint rifles where I shot worse at 100 then at 350. I firmly believe a boolit or bullet can go to "sleep."
It drives me nuts to shoot small groups at 100 with cast in my BPCR and can not hit a ram at 500 no matter what. I watch boolits go way off course. I can bust every pig but after so far the boolit just goes on it's own.
To find a boolit that is linear, 1" at 100, 2" at 200, 3" at 300 is a pipe dream. But it is true that a bullet that does 1" at 100 can shoot smaller at 400.
But no way a 14-1/2" group will be reduced.
Pilgrim stated lighter bullets with slow twists and is correct. Drive faster so spin is up but to mention Greenhill in any context is off.

[Terrence Clarke]

Good work,I often wonder what effect if any that different number of grooves in a barrel would have on the same tests that you have done

[Pilgrim]

I didn't mention # of grooves in my earlier post, but again the HBR folk are plowing new ground (I think, anyway). I dunno what the current flavor is, but 6 or 8 years ago it was 17 twist 3 groove barrels. I'm not entirely sure what the number of grooves has to do with accuracy. Remember the 2 groove military barrels, and the current Marlin microgroove barrels? Both can be made to shoot extremely well. The military 2 groove barrels appear to me the minimum, while the microgroove barrels are at the other extreme. I don't think you could make a single groove barrel work any too well due to bullet imbalance, but any number of grooves 2 or more can be made to work IMO. FWIW Pilgrim

[L Ross]

Impressive amount of work Larry, thanks for sharing.

[dtknowles]

Larry, nice work. I am still not clear on why accuracy deteriorates above the RPM Threshold. I agree you have shown it does but the BC data does not show bullet damage or instability. I can think of a couple suspects but have no way to confirm them. If you have a idea would you care to speculate? One kind of damage that would not show up in the PC data might be if the bullet became unbalanced with the center of mass not on the centerline of the bullet. Not real sure how that could happen but higher RPM would make that damage's affect on accuracy more obvious. Something else that might not show in the BC data but could maybe be seen on the muzzle of the barrel would be if because of skid there was uneven blow by the bullet when exiting the barrel. I know that you said you did not see any lube failures or excessive leading but did you check the muzzle for the lube star and was it even? It might also be possible that it was some other bullet damage that would not show up in the BC data. I don't have a clue what fins or shreds would do to BC data.


Just some stray thoughts, thanks again for sharing.


Tim

[JeffG]

Thank you Larry:)

[Larry Gibson]

.......... I know that you said you did not see any lube failures or excessive leading but did you check the muzzle for the lube star and was it even? It might also be possible that it was some other bullet damage that would not show up in the BC data. I don't have a clue what fins or shreds would do to BC data.

Tim

Here are the muzzles after a HV testing of lubes with the 311466 bullet. The photo is of all 3 test muzzles after 10 shots each with Javelina lube at 2600 fps using the same load in each. Accuracy really sucked with the left 10" twist barrel, just sucked with the 12" twist middle barrel and was very good with the 14" twist right barrel.

Lube star looks good to me considering the psi at exit from the muzzle.

Larry Gibson

108203

[dtknowles]

Here are the muzzles after a HV testing of lubes with the 311466 bullet. The photo is of all 3 test muzzles after 10 shots each with Javelina lube at 2600 fps using the same load in each. Accuracy really sucked with the left 10" twist barrel, just sucked with the 12" twist middle barrel and was very good with the 14" twist right barrel.

Lube star looks good to me considering the psi at exit from the muzzle.

Larry Gibson

108203

Yeah, I would say those look fine, no problem there, so uneven blow by is not the problem.

Tim

[leeggen]

Larry, great info. and you have given a lot of time and effort collecting it for all of us to see.
Bet ya a dollar Felix was watching and he would have been happy with the test results also.
You both give us alot to think about and asorb.
CD

[Larry Gibson]

Wouldn't surprise me in the least. I learned a lot from Felix over the years. He is missed.

Larry Gibson

[TXGunNut]

Thanks, Larry. Well done, well written.

[44man]

Lead is a problem, it is a proven fact that even a tiny wobble with jacketed is no good, why the Juenke tool was developed. Tests showed much increased accuracy when bullets were sorted from the tool.
Molds can't make perfect boolits no matter what. Usually a little out of round and forced through a bore just displaces lead. Even a piece of lube staying in a GG can upset things.
I still appreciate Larry's work.

[Char-Gar]

Larry...You get a giant attaboy! You have given a data and scientific basis to what cast bullet shooters have known and experienced for generations, but could not quantify beyond a few basic things. Good going, truly good going.

Charles...

[popper]

Wonderful data - thanks Larry. I think many who DON'T believe the RPM threshold don't understand 200-300,000 RPM. Stick a 1/32" dremel drill in the tool and crank it up, watch the tip. That's only 35k rpm and a tool steel precision bit. Now imagine that type action on a boolit in flight. It's not RPM but rotational mass (inertia) that does the stabilizing. Can't prove it but those long skinny boolits do flex in flight.

[MBTcustom]

I knew a guy once who didn't believe in gravity. He finally found a cliff that convinced him permanently.

Excellent write up Larry.
You're willingness to provide pictures where most of the holes are in a group and not "called flyers" is commendable. It takes a lot of time money and patience to zero in on specifics like this (as well as being a stone cold, darn good shot), and no matter what our membership takes from your article, I hope they glean the importance of keeping the variables to a minimum so that you can learn something.
I'm still trying to rid myself of the temptation to just throw a bunch of lead into the berm and try to learn something from it later. LOL!

[Centaur 1]

Thanks Larry, the time and effort that you put into this is appreciated. I'm curious about if you ever found the RPM threshold to move downward as bullet diameter increases? I'm thinking about this from a machinist point of view and how you run a larger diameter cutter at a slower spindle speed than a smaller cutter. Even though the cutter is turning slower, edge of the tool is moving at the same S.F.M. (surface feet per minute) as the smaller cutter. Transferring this knowledge to cast bullets, if there is a small imperfection in a cast bullet it would greater effect bullet stability the further it was from the center of rotation.

[btroj]

I knew a guy once who didn't believe in gravity. He finally found a cliff that convinced him permanently.

Excellent write up Larry.
You're willingness to provide pictures where most of the holes are in a group and not "called flyers" is commendable. It takes a lot of time money and patience to zero in on specifics like this (as well as being a stone cold, darn good shot), and no matter what our membership takes from your article, I hope they glean the importance of keeping the variables to a minimum so that you can learn something.
I'm still trying to rid myself of the temptation to just throw a bunch of lead into the berm and try to learn something from it later. LOL!


No Tim, keeping variables to a minimum in a SINGLE test is important.

Multiple variables are to be tested in multiple tests, with one thing being varied at a time.

[swheeler]

Excellent write up Larry and thanks for sharing your work, good job as usual! Imagine one of those 30xcb's chambered in a 15 or 16 twist barrel;) the way it was meant to be done, smokin.

[Digital Dan]

Nice job Larry, thanks!

Uh...I'm going to sleep now. No spin, I win.

[dtknowles]

I bought a used bench rest rifle in 30 BR long with a 1x16 twist barrel but I only have one mould in the right weight range and it does not group. I need to figure out what to buy for a mould to get this rifle to shoot.

Tim

[Larry Gibson]

Thanks Larry, the time and effort that you put into this isappreciated. I'm curious about if you ever found the RPM threshold to movedownward as bullet diameter increases? ...........

One would think so? However I've not got the answer to that yet. Thereare several things at play; if we have an equal defect weight wise it ismost often a much larger % of the mass of the smaller diameter bullet if thebullets are the same length. If we lengthen the smaller bullet to equalizethe weight then where in relation to the center of balance is the defect? If we make the defect equal in mass % then can we detect it with visual or evenby weight sorting? Also is the defect a surface defect or an internalone? If internal then what is it's shape and at what distance is it fromthe COG, COF and center of spin? Answers to those questions I'm notsure of yet.

What I have found is in establishing the RPM threshold with regular castbullets of ternary alloy using the slower fast burning powders to the slowmedium burning powders is the RPM Threshold most often falls between 120,000and 140,000 RPM. This was arrived at by analyzing load and test accuracyresults of .22 cal rifles to rifles of .375 caliber with twists of 7 to12" most often. With the variables involved it is hard to nail downan answer to your question......yet. As we continue with sound testinglimiting the variable to one specific question, as best we can anyway, we getcloser to a lot of answers.

For example; I have controlled the RPM keeping it under 140,000 with the14" twist Palma rifle. When psi's are kept under 40,000 accuracy isexcellent. However, when psi increases to 42,000 psi I get flyers. Not alot out of the group but still flyers. The RPM is still below the RPM threshold at 136 – 137,000 RPM yet theflyers begin. Based on engineercalculations this probably where, at that pressure, some of the bullets beginto plasticize under that rate of acceleration. Thus another variable is thrown in. My solution is to increase case capacity with the 30x57 (30 XCB) to keepthe psi under/at 40,000 psi while increasing velocity. We shall see.

Larry Gibson

[Larry Gibson]

I bought a used bench rest rifle in 30 BR long with a 1x16 twist barrel but I only have one mould in the right weight range and it does not group. I need to figure out what to buy for a mould to get this rifle to shoot.

Tim

What length barrel?

What bullet?

Larry Gibson

[dtknowles]

What length barrel?

What bullet?

Larry Gibson

I will go out an look for a mould number it casts at 130 grains it has one grease groove and a crimp groove with a long ogive and a bevel base. Clearly this is not a great choice of bullet for this rifle but it works OK in my SKS. The barrel is 22 inches long, I think the barrel might be shot out as it will only shoot jacketed into 0.5 MOA at 100 yards with 130 grain Bergers hollow points. I don't really know as the rifling is not far ahead of the chamber and I don't have a BoreScope.

Tim

[dtknowles]

What length barrel?

What bullet?

Larry Gibson

Mould is Ideal 311 410.

Tim

[btroj]

One would think so? However I've not got the answer to that yet. Thereare several things at play; if we have an equal defect weight wise it ismost often a much larger % of the mass of the smaller diameter bullet if thebullets are the same length. If we lengthen the smaller bullet to equalizethe weight then where in relation to the center of balance is the defect? If we make the defect equal in mass % then can we detect it with visual or evenby weight sorting? Also is the defect a surface defect or an internalone? If internal then what is it's shape and at what distance is it fromthe COG, COF and center of spin? Answers to those questions I'm notsure of yet.

What I have found is in establishing the RPM threshold with regular castbullets of ternary alloy using the slower fast burning powders to the slowmedium burning powders is the RPM Threshold most often falls between 120,000and 140,000 RPM. This was arrived at by analyzing load and test accuracyresults of .22 cal rifles to rifles of .375 caliber with twists of 7 to12" most often. With the variables involved it is hard to nail downan answer to your question......yet. As we continue with sound testinglimiting the variable to one specific question, as best we can anyway, we getcloser to a lot of answers.

For example; I have controlled the RPM keeping it under 140,000 with the14" twist Palma rifle. When psi's are kept under 40,000 accuracy isexcellent. However, when psi increases to 42,000 psi I get flyers. Not alot out of the group but still flyers. The RPM is still below the RPM threshold at 136 – 137,000 RPM yet theflyers begin. Based on engineercalculations this probably where, at that pressure, some of the bullets beginto plasticize under that rate of acceleration. Thus another variable is thrown in. My solution is to increase case capacity with the 30x57 (30 XCB) to keepthe psi under/at 40,000 psi while increasing velocity. We shall see.

Larry Gibson


at at some point shooting lots of groups from a bench with a 375 or larger bore rifle just stops being fun. A 300 gr plus bullet at 2400 isn't much fun to shoot lots of groups with, is it?

I sure don't want to be the guy testing a 458 Win mag over long strings from the bench.

[runfiverun]

i'll loan you my browning 45/70 with crescent steel butt plate,, that should soften the blow a tick. :lol:

[btroj]

Bullets are easier to ship than a rifle, how about I send you 200 bullets in the 425 gr range. Let me know how they do in multiple 10 shot groups.

Crescent steel butt plate, 4 words guaranteed to bring tears to the eyes.......

[MBTcustom]

Bullets are easier to ship than a rifle, how about I send you 200 bullets in the 425 gr range. Let me know how they do in multiple 10 shot groups.

Crescent steel butt plate, 4 words guaranteed to bring tears to the eyes.......

Proof that the old timers weren't pushing the RPMTH very much at all.
I've got a buddy with a 458Lott with a steel butplate. It's a real pretty rifle till you see your fillings laying on the bench. LOL!

[runfiverun]

no need to send boolits we run the same load in our 45/70's already...
I dunno the twist rate, so I can't do the math on the rpm's either [but neither can the rifle, so it's fine]

[w30wcf]

Larry,
Thank you for sharing all the information that you have experienced in your "Tale Of Three Twists". Very educational and interesting!:drinks:

w30wcf

[dtknowles]

Is there another (lower) threshold for plain base bullets?

Tim

[GhostHawk]

Thanks to all who have contributed to this incredibly interesting thread.

This right here, is the meat and potatoes of this site, and the reason so many of us keep coming back.

[runfiverun]

ghost hawk:
the meat and potatoes of this site used to be figuring out way's around the rpm windows.

[Eutectic]

ghost hawk:
the meat and potatoes of this site used to be figuring out way's around the rpm windows.

You can say that again, Lamar !!!

Eutectic

[Larry Gibson]

ghost hawk:
the meat and potatoes of this site used to be figuring out way's around the rpm windows.

If one bothers to continue researching what was done and discussed after this thread was original published you'd find this site is still about that. Even before this thread was originally published here several of us were actually pushing the RPM threshold up. Except for the unfortunate fact a few still think and insinuate the RPM Threshold is a "limit" of some sort much has been done to push the RPM threshold up. Those of us who are serious in this endeavor conduct appropriate tests and report the results here in this forum. Others make claims but fail to document those claims through appropriate testing.

Progress is being made. When we understand the actual problem then many times we can solve it. We now know how to push a ternary naked cast bullet to higher RPM before losing accuracy. However, we are only pushing the RPM threshold up as we still are not achieving equal velocity with the same accuracy that the rifles are capable of with jacketed bullets. We also know that if we control the RPM via a slower twist barrel even higher velocity with excellent accuracy can be had. We are even approaching jacketed bullet velocities and accuracy with ternary alloyed naked cast bullets. Numerous members are also expanding our abilities with PP'd cast bullets, with harder alloyed and HT's bullets and now PC'd bullets are showing some real promise. Yes, there is a lot of progress being made on this forum.

Some of us just chose to get on with that progress. Others have chosen to complain and leave because they feel their "old timer" status is threatened. I was on this forum for several years under the old site and have been on this site for a long time. I don't care what a members age is, or what country he is from, or if the spelling isn't great or how many posts he's made. If he has a legitimate question I can help with I will offer advise and try to help. I do a lot of testing to not only provide accurate cast bullet loads for my rifles and handguns but to answer many of the questions as to "why" things happen when we shoot cast bullets. There are the laws of physics and ballistics which we are not really going to get around. Conversely there are many techniques and different ways to get things done. Those are the variables we deal with most often and there are lots of ways to do the same thing. However, when we bump up against a law of physics or ballistics we are not going to change that. What we can do is understand what is happening and then change the variables. That is how we are pushing the RPM threshold up. That is the progress that is being made; we understand the problem and know we can not change the problem so we change the variable to simple move the problem up (in this case to a higher RPM and/or velocity).


So instead of those whining and crying that many do realize there is an RPM Threshold and it is real, how about getting on the band wagon and lets change the variables and move it up. I've already moved it way up by changing the twist variable and am now shooting a ternary alloyed 311466 at 2600 fps with excellent accuracy to a tested and verified 300 Yards. I've posted numerous 10 shot groups to demonstrate that. Another forum member has recently shot that rifle/load at 300 yards and can attest to it.


So how about us continuing to progress instead of regressing?

Larry Gibson

[garym1a2]

Does this mean that I would have better chance of success with a 30-06 to get high velocity than the 308 as I can increase the velocity and not have as much pressure as the 308 would?



One would think so? However I've not got the answer to that yet. Thereare several things at play; if we have an equal defect weight wise it ismost often a much larger % of the mass of the smaller diameter bullet if thebullets are the same length. If we lengthen the smaller bullet to equalizethe weight then where in relation to the center of balance is the defect? If we make the defect equal in mass % then can we detect it with visual or evenby weight sorting? Also is the defect a surface defect or an internalone? If internal then what is it's shape and at what distance is it fromthe COG, COF and center of spin? Answers to those questions I'm notsure of yet.

What I have found is in establishing the RPM threshold with regular castbullets of ternary alloy using the slower fast burning powders to the slowmedium burning powders is the RPM Threshold most often falls between 120,000and 140,000 RPM. This was arrived at by analyzing load and test accuracyresults of .22 cal rifles to rifles of .375 caliber with twists of 7 to12" most often. With the variables involved it is hard to nail downan answer to your question......yet. As we continue with sound testinglimiting the variable to one specific question, as best we can anyway, we getcloser to a lot of answers.

For example; I have controlled the RPM keeping it under 140,000 with the14" twist Palma rifle. When psi's are kept under 40,000 accuracy isexcellent. However, when psi increases to 42,000 psi I get flyers. Not alot out of the group but still flyers. The RPM is still below the RPM threshold at 136 – 137,000 RPM yet theflyers begin. Based on engineercalculations this probably where, at that pressure, some of the bullets beginto plasticize under that rate of acceleration. Thus another variable is thrown in. My solution is to increase case capacity with the 30x57 (30 XCB) to keepthe psi under/at 40,000 psi while increasing velocity. We shall see.

Larry Gibson

[btroj]

So instead of those whining and crying that many do realize there is an RPM Threshold and it is real, how about getting on the band wagon and lets change the variables and move it up. I've already moved it way up by changing the twist variable and am now shooting a ternary alloyed 311466 at 2600 fps with excellent accuracy to a tested and verified 300 Yards. I've posted numerous 10 shot groups to demonstrate that. Another forum member has recently shot that rifle/load at 300 yards and can attest to it

How is changing to a slower twist rate pushing the rpm threshold? You got more velocity for the same rpm but that doesn't "push" anything regarding the rpm threshold.

The "twist variable" isn't really a variable to the majority of members here. Many here won't rebarrel a rifle but will change alloy, mould, or powder along with modifying load technique.

Once a barrel is made the twist is no longer a variable, it is set in steel.

[Larry Gibson]

Does this mean that I would have better chance of success with a 30-06 to get high velocity than the 308 as I can increase the velocity and not have as much pressure as the 308 would?

That it does if both the '06 and the .308W have the same length barrels with the same 10" twist. Proved that numerous years ago when Bass Ackwards and I were testing the LBT bullet and the 311291 and I also did additional testing with the 311466. Both rifles had the same actions and the barrels were from the same manufacturer with the same rifling at 24" with 10" twists. Both rifles shot essentially the same accuracy level just under the RPM Threshold. When we pushed the RPM threshold I could get 100 - 200 fps more out of the '06 than the .308W with the same accuracy with all the bullets because the '06 could use a bit more of the slower burning powders than the .308W at the same psi level. The bit more powder at the same psi meant the higher velocity as the time/pressure curve was still a bit slower in the '06.

Not so easy if the '06 has a 10" twist and the .308W has a 12" twist though. The slower twist/RPM of the 12" twist balances out the case capacity with lower psi of the 10" twist '06.

Larry Gibson

[popper]

I'm trying to decide between 10 or 12 in 300BO, 150 gr like the 041. Powder choice is a problem in that little case. I know the boolit will take the pressure, it's a matter of a good burn. I did a 3d plot of fps, weight, ft-# @ 100 for acceptable load ranges but I can't add twist and it's effects, not accurately anyway.

[garym1a2]

Thanks a lot for you research, I learn quite a bit and it explains why my 1:8 Blackout shoots so well at 1700 fps and probally will not go much faster with cast.

As others say, I may not re-barrel my 1:8 Blackout Ar to shoot faster light boolits but I will look into better twist rates for my next Rifle.


That it does if both the '06 and the .308W have the same length barrels with the same 10" twist. Proved that numerous years ago when Bass Ackwards and I were testing the LBT bullet and the 311291 and I also did additional testing with the 311466. Both rifles had the same actions and the barrels were from the same manufacturer with the same rifling at 24" with 10" twists. Both rifles shot essentially the same accuracy level just under the RPM Threshold. When we pushed the RPM threshold I could get 100 - 200 fps more out of the '06 than the .308W with the same accuracy with all the bullets because the '06 could use a bit more of the slower burning powders than the .308W at the same psi level. The bit more powder at the same psi meant the higher velocity as the time/pressure curve was still a bit slower in the '06.

Not so easy if the '06 has a 10" twist and the .308W has a 12" twist though. The slower twist/RPM of the 12" twist balances out the case capacity with lower psi of the 10" twist '06.

Larry Gibson

[Larry Gibson]

Soinstead of those whining and crying that many do realize there is an RPMThreshold and it is real, how about getting on the band wagon and lets changethe variables and move it up. I've already moved it way up by changing thetwist variable and am now shooting a ternary alloyed 311466 at 2600 fps withexcellent accuracy to a tested and verified 300 Yards. I've posted numerous 10shot groups to demonstrate that. Another forum member has recently shot thatrifle/load at 300 yards and can attest to it
How is changing to a slower twist rate pushing the rpm threshold? You got morevelocity for the same rpm but that doesn't "push" anything regardingthe rpm threshold.

The "twist variable" isn't really a variable to the majority ofmembers here. Many here won't rebarrel a rifle but will change alloy, mould, orpowder along with modifying load technique.

Once a barrel is made the twist is no longer a variable, it is set insteel.

Are we forgetting the goal/objective is high velocity with the ternary alloynaked cast bullet? Changing a barrel is one of the variables. Especially when building a rifle, rebarreling a rifle or reboring arifle. Many here do just that and many are indeed using slowertwists. Several here have had a 30 XCB recently made for them andhandicapped themselves by not using a 14" or slower twist as Ispecified. They also insist on using bore riding bullet designs with longnoses and short bearing surface. I also specified a 26"+ barrellength which none of the recent 30 XCB builders paid any attention toeither. Then they wonder why they run into the RPM threshold. Yes, alot of us have learned and progressed but some have not.


BTW; I have runinto the RPM threshold with my 14" twist Palma barrel rifle. The RPMthreshold for that rifle sits just above 2640 fps which is just above 135,000RPM. The additional problem at that level is pressure. My accuracyload at just over 2600 fps runs 40,000 psi. At the RPM threshold for thePalma rifle it runs 42,000 psi. It appears some of the bullets begin toplasticize at that psi. That is why I designed the 30x57 some years backnow known as the 30 XCB here. That cartridge should give 2700 -2900+ fps (depending on barrel length) at a lower psi which is pushing the RPMthreshold up.

Now back to the essence of your question; how do I push the RPM Threshold upwith the 10" twist whatever I have rifle? Assuming that's your question(?) and you will; “will change alloy, mould, or powder along with modifyingload technique”?

I have answered this question numerous times in the past but will do soagain.

To push the RPM threshold up use bench rest case preparation on your fireformed cases. I necksize the cases to give .002 - .003 necktension. I Mostly use an appropriate sized Lyman M-die to flarethe case mouth (a .31 for .30 cal cartridges with .310 - .311 sized bullets).

Use a standard level primer such as Federal 210s, WLRs, Rem 9 1/2 or CCI200s.

Use as slow a burning powder that will give 80 - 100% load density withconsistent ignition in the 30 - 40,000 psi range. I mostly use RL19, AA4350,H4831SC and RL22. I weigh powder chargesthat do not throw within .2 +/- gr. Iuse a Lyman 55.

Use a cast bulletof appropriate design that has a bearing surface of 60 - 65% minimum, a shortnose and fits in the cartridge neck with the GC seated at the base of the caseneck and the front drive band just off the leade. I find the Loverindesign is working the best.

Use a hard yetmalleable ternary alloy with the antimony and tin balanced and not over 5% ofeach. I WQ my bullets for a BHN of 24 - 26. Be anal when casting; goslow and smooth to cast quality bullets. Be anal in bulletsort/selection. I do a visual inspection (using a large bench mountedlighted magnifying glass)and reject any bullet not perfect; fill out of anydrive band or the shank, holes, wrinkles or rough cratered sprue cut areall reasons to reject. I reject probably 40 - 50% of the bullets onthis visual inspection. Those are usually pretty good bullets and mostly getshot with accurate loads in other rifles below the RPM threshold. Theyare just not good enough for this purpose. I take the remaining bulletsthat passed the visual inspection and then weight sort them. I usuallyend up with about 50 - 60% of the 311466s within +/- .4 gr of eachother. Those are the bullets I use for HV loads to push the RPM Thresholdwith. The same anal selection process should apply to any otherbullet. The bullets should be as perfect as possible and within +/- .5 ofone % of each other weight wise.

I seat the GCseparately using Hornady GCs, usually with the GC seater in the Lyman 450. I size the bullet as close to "as cast" as possible if it fits thethroat of the chamber. I usually find a cast bullet sized at .0015 -.003 over the groove diameter will shoot the best. The diameter of the throatand the length of throat usually determine the sizing of the bullet as you wantthe bullet to “slip into the throat and the barrel with a very good fit butwith as little resistance from sizing the bullet as possible. I lube all thegroves with a soft lube that will purge from the bullet within 20' of themuzzle.

Work up theloads and use a sufficient sample; sorry but 3 and even 5 shots isn’t it. Yes you’ve a lot of care gone into selectingthe cast bullets to test. You haverejected a lot of them but now is not the time to scrimp on too small a testsample. Use 10 shots preferably. If youcall a shot bad then the remaining 9 “good” shots will still give you gooddata. Use a solid test bench with a goodrest (doesn’t have to be expensive but good is imperative). Use good bench shooting technique. Don’t shoot too fast and keep the barrelcool. Test at 100 yards initially. A shorter range will tell you nothing. Do notignore flyers if they are not a called shot that goes to call. Flyers are telling you something, don’tignore them.

Chronographyour test strings. If you don’t you’reonly guessing at the velocity and RPM. The max effective range of a guess is zero meters. The ES and SD will also provide good measuresof consistent loads.

Maintain goodrecords.

When you thinkyou have a good load then load up 25 test rounds. Shoot 5 shots to foul the barrel; shootslowly so to not heat the barrel up too much. Then shoot a 10 shot group at 100 yards. Let the barrel cool and then shoot a 10 shot group at 200 yards. If the 10 shot 100 yard group is good but the200 yard group is more than twice the size then the load exhibits non linearexpansion and the RPM threshold is exceeded. Be a bit reasonable here as the chance of exactly twice the size isremote. If the 100 yard group is 1.5”for example and the 200 yard group is within say 3 – 4.5” then you have a goodload with probable linear expansion that is not exceeding the RPMThreshold. However if the 200 yard groupwas say 5 – 8” then the load exceeds the RPM Threshold and accuracy as therange increases will get much worse.

Let us considera different perspective; if it’s a hunting load then that 5 – 8” group at 200yards may be entirely acceptable as you never shoot game past 150 yards. Thus, even though the load exceeds the RPMThreshold it still then is a “useable” load, at least in my opinion.

However, ifaccuracy is the name of the game at HV then that load won’t do unless the 200 yardgroup is very close to twice the size of the 100 yard group. If that’s the case then load up 30 morerounds and test again with 10 shot groups at 100, 200 and 300 yards. If the linear dispersion is correct then the200 yard group will be about twice the 100 yard group and the 300 yard groupwill be 3 times the size of the 100 yard group. When that happens you have an excellent load.

Now if you areexpecting jacketed bullet velocity with the same accuracy using cast bullets withyour 10” or faster twist barrel then you might consider adding copper to thealloy and heat treating it, PPing or perhaps PCing.

We have learnedand we have progressed but some of us understand there are some things on ourbeloved cast bullets, especially the plain ternary alloyed naked ones areprobably just not going to do. Thus toachieve our goal of HV with such a cast bullets we do what is necessary toachieve it such as; rebarrel with a slower twist, use a different alloy, use adifferent bullet design, use a different powder and modify our loadingtechniques. We do this to achieve an achievablegoal.

Larry Gibson

[btroj]

Interesting, my barrel should be finishing out at 28 inches or just over. I suppose that was never stated but I'm amazed Tim never shared that info with you. Then again it was clearly stated in post 57 of the XCB thread that you participated in. Here is what I stated on 10/1/13

My barrel is a Palma taper Krieger. One in 12 twist, should finish to 30 inches or so. It will go on a Savage action and be put in a BR type laminate stock. It will be heavy and that is fine with me. It will never see use in the filed, I wanted a pure target type rifle.

Changing to a slower twist doesn't "push" the threshold at all, it reduces the rpm for the same velocity. It gives you more velocity for the same rpm but it doesn't in any way "push" the RPMs.

I am all for changing load techniques, alloys, and moulds. Those are true, viable, variables that everyone here can comprehend and afford. I'm not looking to make change that benefit gunsmiths or barrel manufacturers, I'm looking for changes the average Joe can understand and make.

[MBTcustom]

I understand where you are coming from Larry. You are very well written and you seem to know how to use a camera, notebook, and keyboard nearly as well as a trigger.
The work you have done here is commendable, as most people are perfectly happy running their rifles well within the RPMTH and that is the truth. That is what is reproducible in any rifle, and the rest of this is either cutting edge boolitry, wishful thinking, or wild speculation.
I personally believe there is a place beyond the RPMTH where something very interesting might happen. I base this belief on all the people who say they did it (never mind the fact that for them the keyboard is a much handier piece of electronics than a digital camera or the English language).
I hope to find a load that runs well above the RPMTH someday. It's a tantalizing goal that I just cant shake (any goal worthy of perusing will be elusive after all!) but I have read some of your posts, and I think that rather than a pot at the end of the rainbow, the RPMTH is real, tangible, provable, and consistent.
I have been told that the "secrets" to HV cast lead shooting is posted here for anyone who cares to dig it up, but I have been searching the archives for months and while I find many jabs, sneers, trolls, allusions, carrots, rabbit holes, "groups" in the middle of shotgun blasts, unfinished tests, unexplained results, and "how dare you ask for anything better than this toiletry" comments, I trip over your writings just as often, and they are filled with careful explanations (based on science and documentation) pictures, demonstrations, and references to respected sources.
I may not come to the exact conclusions you have, but if you are looking to gain my respect, this is the way to do it.
I see nothing like this from people who claim anything different/better. I gave my undivided ear and friendship to some of these, and I found nothing but bigotry, ignorance, and an absolute inability to formulate the simplest tutorial, explanation, or logical argument. In fact, they only succeeded in convincing me that you are 100% right as rain. It took a while, but they talked me right out of their point of view.

Now as to the XCB rifles, there are only 4 now in existence.
One for geargnasher (you might not have noticed it because he has posted precious little about it since I delivered it to him)
One for btroj (nearing completion)
One for Lamar (also nearing completion but not finished)
and one for me which is assembled but only 15 shots have been taken with it (hooray! it didn't blow up!)
My rifle was made with a Remington 700 takeoff barrel because that was all I could afford. It's 21.5" long and 1-10 twist. Believe me, I wish I could afford a slow twist Kreiger, but I'm too busy building them for other people for peanuts to be able to drop that money on myself.
I know the twist is wrong, and so is the barrel length, but I'm not trying to prove anything. I just wanted a fun rifle to mess with, and if I learn something in the process, then I'm happy. I am going to be finding the RPMTH with this rifle, and experimenting with low velocity accuracy, but I also want to load it up to the gills and see how bad I can lead it up. LOL! One thing is for sure: Since I am gentleman enough to give every man his own space, and recognize each person for where they are and where they come from, it seems I will be doing this alone without the help of the self proclaimed "experts".
Who knows? maybe I'll find that pot of gold at the end of the rainbow? I can assure you that I will have fun in the process and I will post pictures of groups as well as (gasp) documentation of what I did and how I did it, and exactly how badly it sucked or didn't. One thing is certain though, and I make no bones about it: I will not ignore clearly written science, nor the laws of physics. If I find a place above the RPMTH that accuracy is attainable and reproducible, and I succeed in doing so, it will square with the RPMTH. It could be there are nodes of accuracy and each projectile has two or three RPMTH's? Perhaps the terminology will change, but the science never will.
It's all good.

[Larry Gibson]

That's great, but what's the twist? Go back and read the thread "we" participated it and see what twist I recommended.

As to what is "pushing the RPM threshold up" I guess your definition of "is" is different than mine. Makes no difference as the goal is the same. Besides I've already explained ad nauseum about pushing the RPM Threshold up according to your definition in my own rifles of "fast" twist. If you doubt that then go have a look at my 6.5 Swede thread. Look at the accuracy I was getting at 2100+ fps which is 197,000+ RPM. Does that meet your criteria? If so then read how I did it and note the description of how above; they are the same technique. I can give you more examples but I'm wasting my breath as I've explained it all to you before. Now soon you'll have a very fine rifle with an excellent 12" twist long barrel in a very good cartridge for the purpose. The normal RPM threshold for the 12" twist will be from about 2000 fps to 2335 fps (120 - 140,000 RPM). To bad you didn't go with a 14" twist. However, do things right and lets see if we can "push" the RPM threshold up with that longer barrel by using a slower powder to lesson the time/pressure curve and with a bullet of proper design. Perhaps you'll learn how it's done?

Speaking of the bullet; what is your intended cast bullet?

Powder?

Larry Gibson

[btroj]

I don't have a single bullet or powder in mind. I will try what I think will work and see what happens. Alloy will be varied as well.

tim, ever think you found what you looked for because you had already decided what you believed?

[MBTcustom]

tim, ever think you found what you looked for because you had already decided what you believed?

Absolutely.
I believe in science. I believe in honesty. I believe in being a gentleman. I believe in doing to others as I would have them do to me. I believe in telling the truth (to myself first, and then to everyone else). I believe that doing the right thing toward a complete stranger is more important than bending the truth to preserve a friendship. I believe in moderating evenly no matter who is trying to whisper in my ear.
Yep, I have no place for people who believe otherwise, or troll peoples hard work or a different point of view.

[swheeler]

Absolutely.
I believe in science. I believe in honesty. I believe in being a gentleman. I believe in doing to others as I would have them do to me. I believe in telling the truth (to myself first, and then to everyone else). I believe that doing the right thing toward a complete stranger is more important than bending the truth to preserve a friendship. I believe in moderating evenly no matter who is trying to whisper in my ear.
Yep, I have no place for people who believe otherwise, or troll peoples hard work or different point of view.

By gawd I think we believe in the same things!

[Eutectic]

Let’s now take a look at the results on target. After all whatwe are looking at in conducting this test isthe accuracy at higher velocity and why that accuracy goes bad. Graph #4 showsus the group sizes vs pressure. Whoa there! Something is amiss….if the timepressure curves are the same, the acceleration the same and the BCs are thesame; then if the groups get larger as we increase velocity shouldn’t thegroups get larger by proportionally the same amount? [Note; by “proportionalamount” is an amount to compare the accuracy of each twist to each other. Theproportional amount factor of increase is found by dividing the increased groupsize by the smallest group with each rifle.] However, what we see is that thegroups do not get proportionally larger as velocity increases. The inaccuracyof the 10” twist increases by a factor of 5.38 while the inaccuracy of the 12”twist increases by a factor of 3.14 and 14” twist increases by a factor of 2.08.
Larry Gibson


Larry,

Your 'proportional amount' is talking to you (us).... It may be in a language we don't understand at the moment. But it's a clue to success......

While I understand your goal here; I think your use of the term 'RPM Threshold' is giving too much credit to a variable which has many variables already in its makeup. I certainly am not discrediting all your hard work on this! You are working hard for some repeatable baselines which is good. Please let me throw out some thoughts as this is not my first rodeo.

"RPM".... This term is usually used for the rotational speed of an object that rotates in a stationary position. Our boolit has both rotational speed and linear (forward motion) speed. An engineer can calculate the RPM of a cast iron flywheel and the resulting surface feet per minute to know if said flywheel is safe at that RPM. Our boolit is adifferent story...

Let's take your 14" twist gun for our example. You know the muzzle velocity from your chronograph. So some simple calculations gives us an "RPM". IS THIS A REAL NUMBER?
Put another way..... when your boolit leaves the barrel is it in fact making ONE REVOLUTION IN 14"? How about 100 yards? I've tested a lot on these questions; so let me answer: One revolution in 14"? The boolit can make one revolution in 14" just out of the gun. BUT IT MIGHT NOT AS WELL! At 100 yards? NO! The distance traveled per revolution becomes LESS! It will continue to change and will not be 14" again! I've proven this and so has Mann over one hundred years ago. This is the definition of "going to sleep" by the way.

Bottomline... Being RPM is related to distance in our case with our boolit; it is a variable in its own right and not necessarily accurate or trustworthy.

Let me throw out what may be causing the proportional amount discrepancy you are seeing... I think maybe 'torsional distortion' ... Almost ALWAYS for me when I see a serious accuracy degradation with fast twists at fast speeds; and if I can find or recover a fired boolit; I see WIDER land engravings on the boolit than actual land width! This 'torsional distortion' can really mess with distance traveled per revolution!

Your thoughts on more 'bearing' surface on the boolit is a good one Larry... I agree if HV is the goal. But if we think what is imparting our 'spin' to our boolit, the length is short. Even 5/8" is little to guide one turn in 14" as we leave the muzzle. With a perfect boolit/rifling fit you'll guide the rotation to 1 in 14"... If you wallow out the land travel you might get anything for 1 in ??" 'Torsion distortion' is aggravated as the twist goes faster for any given velocity that initiates it.

I think I would add your same exact test boolits, but sized down and paper patched to the equation... I know you want to achieve a 'bare boolit' application... But this would be a good indicator if 'torsional distortion' was the culprit of your 'proportional amount' changes if they suddenly improved using a boolit with better traction!

Eutectic

[Larry Gibson]

Eutectic

Your 'proportional amount' is talking to you (us).... It may be in a language we don't understand at the moment. But it's a clue to success......

I think you are misunderstanding what I meant by "proportional amount(?). The "proportional amount" I refer to is simple a quantification of the difference in accuracy capability between the 3 rifles. Let's say at the best accuracy (intrinsic accuracy) one barrel produces with the best of match jacketed bullets is 1.3 moa accuracy, the 2nd barrel 1.6 moa and the 3rd barrel 1. 75 moa. Then with our cast bullet load the 1st barrel gives 1.95 moa, the 2nd barrel 2.4 moa and the third barrel gives 2.6 moa. We can say the accuracy is consistent because each load is about 1.5% of the intrinsic accuracy with each barrel when it is compared to it's own intrinsic accuracy. However, if the same load then produces 3.1 moa in the 1.3 moa barrel and 2.6 moa in the 1.75 moa barrel we know something is afoot as the "proportional amount" is now askew at 1.5% to 2.4% difference. Basically "proportional amount" is comparing the accuracy difference of each barrel to itself before we compare it between the barrels.

While I understand your goal here; I think your use of the term 'RPM Threshold' is giving too much credit to a variable which has many variables already in its makeup. I certainly am not discrediting all your hard work on this! You are working hard for some repeatable baselines which is good. Please let me throw out some thoughts as this is not my first rodeo.

The title simply is a title. The RPM creates centrifugal force which is the real culprit. There are a lot of variables which is why the RPM threshold is not a hard and fast figure or "limit" as some want to think. The RPM Threshold is that point generally between 120- 140,000 RPM where, because of the many variables, that accuracy will begin to degrade.

"RPM".... This term is usually used for the rotational speed of an object that rotates in a stationary position. Our boolit has both rotational speed and linear (forward motion) speed. An engineer can calculate the RPM of a cast iron flywheel and the resulting surface feet per minute to know if said flywheel is safe at that RPM. Our boolit is adifferent story...

Let's take your 14" twist gun for our example. You know the muzzle velocity from your chronograph. So some simple calculations gives us an "RPM". IS THIS A REAL NUMBER?
Put another way..... when your boolit leaves the barrel is it in fact making ONE REVOLUTION IN 14"? How about 100 yards? I've tested a lot on these questions; so let me answer: One revolution in 14"? The boolit can make one revolution in 14" just out of the gun. BUT IT MIGHT NOT AS WELL! At 100 yards? NO! The distance traveled per revolution becomes LESS! It will continue to change and will not be 14" again! I've proven this and so has Mann over one hundred years ago. This is the definition of "going to sleep" by the way.

Would like to see how you've managed to "prove" that. It is a ballistic fact that rotational speed of the bullet degrades very, very little over the normal muzzle to target distances (0 to 1000+ yards) How do we "know" the rotation is 1 in 14" out of a 1 in 14" twist barrel? Law of physics says a body in motion tends to stay in motion unless acted upon by another force. The bullets velocity decreases because it is acted upon by another force; the air density. The rotational force degrades very, very little (there are calculation formulas for this in most ballistic books btw) because there is little to no air resistance or another force to act upon a stabilized bullets rotational speed. So out of a 1 in 14" twist barrel we can say for certainty the stabilized bullet is making 1 turn in 14" and thus correctly calculate the RPM on that.

Bottomline... Being RPM is related to distance in our case with our boolit; it is a variable in its own right and not necessarily accurate or trustworthy.

Bottom line that is an incorrect assumption. Would the bullets rotational speed slow down that quickly the bullet would then lose rotational stability at a very close range and we could not shoot the distances we do with accuracy and bullets would not have the maximum ranges they do. It is proven that the rotation sped does not slow down appreciably

Let me throw out what may be causing the proportional amount discrepancy you are seeing... I think maybe 'torsional distortion' ... Almost ALWAYS for me when I see a serious accuracy degradation with fast twists at fast speeds; and if I can find or recover a fired boolit; I see WIDER land engravings on the boolit than actual land width! This 'torsional distortion' can really mess with distance traveled per revolution!

And what then would cause this "torsional distortion" to make the bullet inaccurate by not following the line of flight? Let me answer that; "torsional distortion" imbalances the bullet by moving alloy and thus moving the center of gravity away from the center of spin. And then pray tell what causes the center of gravity not coinciding with the center of form and the center of spin to lose accuracy? Centrifugal force is what. And then where does centrifugal force come from? The answer is RPM.

Your thoughts on more 'bearing' surface on the boolit is a good one Larry... I agree if HV is the goal. But if we think what is imparting our 'spin' to our boolit, the length is short. Even 5/8" is little to guide one turn in 14" as we leave the muzzle. With a perfect boolit/rifling fit you'll guide the rotation to 1 in 14"... If you wallow out the land travel you might get anything for 1 in ??" 'Torsion distortion' is aggravated as the twist goes faster for any given velocity that initiates it.

The % of bearing surface to bullet length is not important for the reason of "imparting spin" to the bullet. It's importance comes from it keeping the bullet aligned concentrically from case to throat, in the throat through engraving on the lands and in supporting the entire bullet. The more of the bullet we have at groove diameter the less there is to bend, slough or obturate in any direction to imbalance the bullet. That long bore rider has a lot of leverage to bend, slough, or obturate it one side or the other into the .003 - .004 (usual groove depth). Also in the case of the Loverin designed bullet the lube in all those groove is not very compressible (laws of hydraulics) and supports the bearing surface as does a PP or jacket somewhat. You don't have that with the shorter bearing surface long nose bore riders. Even with a 50/50 land to groove ratio you still have 50% of the bore rider nose that is unsupported. None of the bearing surface is unsupported. Thus it is better to have more bearing surface and less nose.

I think I would add your same exact test boolits, but sized down and paper patched to the equation... I know you want to achieve a 'bare boolit' application... But this would be a good indicator if 'torsional distortion' was the culprit of your 'proportional amount' changes if they suddenly improved using a boolit with better traction!

Not necessarily so as the PP does a lot more than simply provide "a boolit with better traction". If you (I already have) tested a pure lead, a COWW and a linotype cast bullets PP'd and worked up loads from 1800 fps to 3000 fps in a 10" twist '06 you will find that even PP'd bullets have an "RPM Threshold". Actually jacketed bullets do to. The RPM Thresholds are just higher.

Your input is appreciated and has given us additional food for thought. You're actually pretty correct on a lot but are only looking at the obvious and not yet seeing the root causes. Look deeper with the laws of physics and ballistics in mind and you will see many of the "variables" we can change and affect. However, the laws of physics and ballistics we can not change but we can affect them by changing the variables.

Larry Gibson

[Eutectic]

Larry,


Eutectic

Your 'proportional amount' is talking to you (us).... It may be in a language we don't understand at the moment. But it's a clue to success......

I think you are misunderstanding what I meant by "proportional amount(?). The "proportional amount" I refer to is simple a quantification of the difference in accuracy capability between the 3 rifles. Let's say at the best accuracy (intrinsic accuracy) one barrel produces with the best of match jacketed bullets is 1.3 moa accuracy, the 2nd barrel 1.6 moa and the 3rd barrel 1. 75 moa. Then with our cast bullet load the 1st barrel gives 1.95 moa, the 2nd barrel 2.4 moa and the third barrel gives 2.6 moa. We can say the accuracy is consistent because each load is about 1.5% of the intrinsic accuracy with each barrel when it is compared to it's own intrinsic accuracy. However, if the same load then produces 3.1 moa in the 1.3 moa barrel and 2.6 moa in the 1.75 moa barrel we know something is afoot as the "proportional amount" is now askew at 1.5% to 2.4% difference. Basically "proportional amount" is comparing the accuracy difference of each barrel to itself before we compare it between the barrels.

No, I understood what you meant Larry. That increased % of in-accuracy is what I said was talking to us.

While I understand your goal here; I think your use of the term 'RPM Threshold' is giving too much credit to a variable which has many variables already in its makeup. I certainly am not discrediting all your hard work on this! You are working hard for some repeatable baselines which is good. Please let me throw out some thoughts as this is not my first rodeo.

The title simply is a title. The RPM creates centrifugal force which is the real culprit. There are a lot of variables which is why the RPM threshold is not a hard and fast figure or "limit" as some want to think. The RPM Threshold is that point generally between 120- 140,000 RPM where, because of the many variables, that accuracy will begin to degrade.

"RPM".... This term is usually used for the rotational speed of an object that rotates in a stationary position. Our boolit has both rotational speed and linear (forward motion) speed. An engineer can calculate the RPM of a cast iron flywheel and the resulting surface feet per minute to know if said flywheel is safe at that RPM. Our boolit is adifferent story...

Let's take your 14" twist gun for our example. You know the muzzle velocity from your chronograph. So some simple calculations gives us an "RPM". IS THIS A REAL NUMBER?
Put another way..... when your boolit leaves the barrel is it in fact making ONE REVOLUTION IN 14"? How about 100 yards? I've tested a lot on these questions; so let me answer: One revolution in 14"? The boolit can make one revolution in 14" just out of the gun. BUT IT MIGHT NOT AS WELL! At 100 yards? NO! The distance traveled per revolution becomes LESS! It will continue to change and will not be 14" again! I've proven this and so has Mann over one hundred years ago. This is the definition of "going to sleep" by the way.

Would like to see how you've managed to "prove" that.

Larry, I take it you haven't read Franklin Mann's book?

I am not to keen about posting proof as it created quite a stir last time! If you remember some five years ago we had a rather heated thread on this 'proof'. Not you and I, but another that adamantly argued a boolit COULDN'T make one revolution downrange in a length less than the twist length of the gun it was shot in. He was wrong and didn't like it much.....

It is a ballistic fact that rotational speed of the bullet degrades very, very little over the normal muzzle to target distances (0 to 1000+ yards)

Why my above statement is true.... Sorry you misunderstood I didn't know this.

How do we "know" the rotation is 1 in 14" out of a 1 in 14" twist barrel? Law of physics says a body in motion tends to stay in motion unless acted upon by another force.

Like 'torsional distortion' maybe?

The bullets velocity decreases because it is acted upon by another force; the air density. The rotational force degrades very, very little (there are calculation formulas for this in most ballistic books btw) because there is little to no air resistance or another force to act upon a stabilized bullets rotational speed.

So out of a 1 in 14" twist barrel we can say for certainty the stabilized bullet is making 1 turn in 14" and thus correctly calculate the RPM on that.

Certainty may not be correct Larry. If the boolit loses its 'locked in' grip (Like widened land runners maybe) You may just lose you 1 in 14" with some certainty.....

Bottomline... Being RPM is related to distance in our case with our boolit; it is a variable in its own right and not necessarily accurate or trustworthy.

Bottom line that is an incorrect assumption. Would the bullets rotational speed slow down that quickly the bullet would then lose rotational stability at a very close range and we could not shoot the distances we do with accuracy and bullets would not have the maximum ranges they do. It is proven that the rotation sped does not slow down appreciably

Sorry Larry.... That was a poor way of wording my sentence The distance I spoke of was the 14" twist to determine probable RPM.

Let me throw out what may be causing the proportional amount discrepancy you are seeing... I think maybe 'torsional distortion' ... Almost ALWAYS for me when I see a serious accuracy degradation with fast twists at fast speeds; and if I can find or recover a fired boolit; I see WIDER land engravings on the boolit than actual land width! This 'torsional distortion' can really mess with distance traveled per revolution!

And what then would cause this "torsional distortion" to make the bullet inaccurate by not following the line of flight? Let me answer that; "torsional distortion" imbalances the bullet by moving alloy and thus moving the center of gravity away from the center of spin.

Not necessarily Larry... The 'torsional distortion' caused by high velocity, higher pressures, and steeper twists. Maybe all three... This distortion can displace metal evenly around the circumference of our boolit by widening land engraved width. You could still be in balance but you may not stay against the lands' driving edge... Humm?

And then pray tell what causes the center of gravity not coinciding with the center of form and the center of spin to lose accuracy? Centrifugal force is what. And then where does centrifugal force come from? The answer is RPM.

Your thoughts on more 'bearing' surface on the boolit is a good one Larry... I agree if HV is the goal. But if we think what is imparting our 'spin' to our boolit, the length is short. Even 5/8" is little to guide one turn in 14" as we leave the muzzle. With a perfect boolit/rifling fit you'll guide the rotation to 1 in 14"... If you wallow out the land travel you might get anything for 1 in ??" 'Torsion distortion' is aggravated as the twist goes faster for any given velocity that initiates it.

The % of bearing surface to bullet length is not important for the reason of "imparting spin" to the bullet.

It may be important to 'hold' our "imparted spin" as we push the envelope though???

It's importance comes from it keeping the bullet aligned concentrically from case to throat, in the throat through engraving on the lands and in supporting the entire bullet. The more of the bullet we have at groove diameter the less there is to bend, slough or obturate in any direction to imbalance the bullet. That long bore rider has a lot of leverage to bend, slough, or obturate it one side or the other into the .003 - .004 (usual groove depth). Also in the case of the Loverin designed bullet the lube in all those groove is not very compressible (laws of hydraulics) and supports the bearing surface as does a PP or jacket somewhat. You don't have that with the shorter bearing surface long nose bore riders. Even with a 50/50 land to groove ratio you still have 50% of the bore rider nose that is unsupported. None of the bearing surface is unsupported. Thus it is better to have more bearing surface and less nose.

I understand this point Larry. "Bore riders" do seem more correct for accuracy from a design
perspective... but I fight them more times than not!

I think I would add your same exact test boolits, but sized down and paper patched to the equation... I know you want to achieve a 'bare boolit' application... But this would be a good indicator if 'torsional distortion' was the culprit of your 'proportional amount' changes if they suddenly improved using a boolit with better traction!

Not necessarily so as the PP does a lot more than simply provide "a boolit with better traction". If you (I already have) tested a pure lead, a COWW and a linotype cast bullets PP'd and worked up loads from 1800 fps to 3000 fps in a 10" twist '06 you will find that even PP'd bullets have an "RPM Threshold". Actually jacketed bullets do to. The RPM Thresholds are just higher.

Granted, one can 'push' any of them hard enough to create centrifugal force problems outside the bore. My comment was for a suspected in the bore problem I call 'torsional distortion'.... maybe circumferential distortion would be more clear? At any rate, what you were shooting could be handled with PP even at 1 in 10" with ease as hard a boolit as you were using.

Your input is appreciated and has given us additional food for thought. You're actually pretty correct on a lot but are only looking at the obvious and not yet seeing the root causes. Look deeper with the laws of physics and ballistics in mind and you will see many of the "variables" we can change and affect. However, the laws of physics and ballistics we can not change but we can affect them by changing the variables.

Larry Gibson

[Larry Gibson]

Eutectic

Yes, I have read Mann's book and find nothing there that says the bullet RPM is faster than it is at the muzzle. Is that what you are inferring? The RPM changes very little down range and the centrifugal remains consistent. The slow increasing helical arc or the bullets flying off on a tangent to the line of flight is a result of that. We have proof of that with the results on the targets posted. I'm not sure what your trying to say?

Not necessarily Larry... The 'torsional distortion' caused by high velocity, higher pressures, and steeper twists. Maybe all three... This distortion can displace metal evenly around the circumference of our boolit by widening land engraved width. You could still be in balance but you may not stay against the lands' driving edge... Humm?

I would refer you to the test results. What you say is nice in theory and is argued ad nauseum by a couple in previous threads. The tests here disprove that the faster twists do not really raise the psi. Also if the acceleration/velocity is equal the obturation, set back, soughing or bending would be the same. Also if the bullet was "still in balance" then the centrifugal force would have nothing to act on and accuracy would be equally proportionate. Fact is if, at a given velocity, the centrifugal force will be greater in a faster twist. Thus the adverse affect on accuracy is greater. That's why the 10" twist loses accuracy at a lower velocity; the centrifugal force is greater as the RPM is greater than in the 12 or 14" twist at the same velocity.

It may be important to 'hold' our "imparted spin" as we push the envelope though???

As mentioned that is part of it.

I understand this point Larry. "Bore riders" do seem more correct for accuracy from a design
perspective... but I fight them more times than not!

Exactly! What seems "more correct" doesn't mean that it is.

As to your argument to PP, I suggest you have at it. As stated the purpose of this test is to determine the RPM Threshold of naked cast bullets of a ternary alloy. That has been done. My follow up tests have also proven excellent accuracy can be had by controlling the RPM via a slower twist, still with naked cast bullets of a ternary alloy. My intention is to see how high in velocity we can push the naked cast bullet of ternary alloy and that is my direction. There is a "Start a Thread" button. I suggest you work the PP'd bullet question since that seems your interest. I'll be glad to help on your new thread but this thread isn't the place for it.....that would make this :hijack:

Larry Gibson

[Larry Gibson]

goodsteel

Not a problem with the 21.5" barrel on your 30 XCB. I shall be glad to help you wring out the best we can. That is the same I extend to btroj. No, I don't think they are the right twist (and yours the barrel length also) to ring out the best the cartridge may offer but I am more than willing to help prove me wrong. Be my pleasure.

Larry Gibson

[MBTcustom]

goodsteel

Not a problem with the 21.5" barrel on your 30 XCB. I shall be glad to help you wring out the best we can. That is the same I extend to btroj. No, I don't think they are the right twist (and yours the barrel length also) to ring out the best the cartridge may offer but I am more than willing to help prove me wrong. Be my pleasure.

Larry Gibson

Hopefully I can have a good time "wringing it out" without bringing "who's right and who's wrong" into the experience at all. I think we both agree that the rifle is right. Always has been, always will be. First thing I want to do is find the RPMTH for my 21.5" X 1-10 twist barrel and see how it compares to your results up yonder. I'm hoping to get a chance to shoot soon. I'll be sure to bring my camera.

Once that is established, I will load up and test till I flatten the primers ( I expect to be able to get nearly 2900fps before that happens), and I will document what the groups do. I expect of there is any semblance of a higher RPM/FPS accuracy potential, that I would see the patterns constrict at a certain point. If that happens, then I will experiment more right in that area. If the groups just get more and more terrible then I wouldn't think there would be anything to investigate further.
We'll see.
Maybe I'll get there by Christmas. LOL!

[35 shooter]

goodsteel i for one will be looking forward to your tests with that rifle.From what little i know at this point about the rpmth you certainly have a twist rate to challenge it head on with. I guess i mean if you blow by it at some point with 1/10 twist and accuracy returns then i should be able to bring the thunder with my 1/14" easier. I fall on the rpm side of things mostly because i keep shaking hands with it at the range and Larry does such a good job of explaining what's going on that has me scratching my head at times.
If you want to take it head on to see what happens i think you made the right choice to do it with and it should be fun to try. Even if you don't find anything "beyond", your still gonna have one accurate rifle where ever it chooses to shoot at. I'll be watching this for sure and won't be dissapointed whatever the results.

[MBTcustom]

goodsteel i for one will be looking forward to your tests with that rifle.From what little i know at this point about the rpmth you certainly have a twist rate to challenge it head on with. I guess i mean if you blow by it at some point with 1/10 twist and accuracy returns then i should be able to bring the thunder with my 1/14" easier. I fall on the rpm side of things mostly because i keep shaking hands with it at the range and Larry does such a good job of explaining what's going on that has me scratching my head at times.
If you want to take it head on to see what happens i think you made the right choice to do it with and it should be fun to try. Even if you don't find anything "beyond", your still gonna have one accurate rifle where ever it chooses to shoot at. I'll be watching this for sure and won't be dissapointed whatever the results.

Well, it sounds like we are in the same boat. I have kept an open mind on this subject for months (almost years) and after spending hours on the phone, on line, and at the range, I found there was an overwhelming amount of evidence to support Larry's position. Three of my rifles (OK, three of my barrels) have confirmed Larry's position as shockingly accurate and true. In fact, in all that time, I gave the naysayers my full, undivided attention and ear. Pretty much all I got was that Larry is wrong because Larry is just wrong. No argument that RPM is the force that acts on imbalances (three separate critics admitted this to me over the phone). No evidence to the contrary. No logical reasoning. Nothing but emotionally charged accusations and random information.

I rebarreled a rifle for one person free of charge, hoping he could provide me with something solid. I never heard anything more about this "high velocity cast boolt shooting that anybody can do." yet he continued to troll Larry, even in my threads, asking for proof while providing nothing on his part.
I built a custom scope mount from scratch for another of these free of charge, and I got the worst cussing of my life via e-mail because I wouldn't discard the RPMTH and asked for a cessation of hostilities over the issue.
I am currently building a rifle for another, free of charge, who seems to have made it his mission in life to troll any thread dealing with this issue, in spite of his horribly obvious lack of providing one shred of empirical data to the contrary (or of anything else for that matter).

Well I've had it with leprechauns with crummy attitudes and not a gold coin about their person and barely the faintest hint of a rainbow to point at. I'm interested in science and facts. I have not discounted anything that anyone has claimed, but since I have to be a hating troll in order to get that pot at the end of the rainbow, I'm going my own way and running some tests that might actually mean something to somebody with half a brain.
Since I can't stick any of these people except Larry in the same room with logical thought, then I will have to run my own tests and come to my own conclusions. My mind is still wide open, but I have accepted the RPMTH as a very valid measure of success.

BTW, I have assembled a new group of shooters. Each are true booliteers with a level head and an eye on science. They will each be provided an XCB rifle, and I have high hopes that real results will be forthcoming.
The rifles will be in 10, 12,14, and 16 twist. I took the 10 because I'm an incorrigible masochist.......obviously. LOL!

[frnkeore]

Thanks a lot for you research, I learn quite a bit and it explains why my 1:8 Blackout shoots so well at 1700 fps and probally will not go much faster with cast.

As others say, I may not re-barrel my 1:8 Blackout Ar to shoot faster light boolits but I will look into better twist rates for my next Rifle.

Don't give up on your 8 twist rifle. You just need the proper throating and a little load delevopement.

This what a 9 twist can do at 160,000 rpm :

CBA match at Tamaqua, PA

Bottiger, Jerry, Cartidge, 7mm BR - Barrel, Shilen 23" lg, 9 twist - Weight, 12.62 lb - Scope, Weaver 36x

Bullet, NEI 170, Nose .276, Band .285 - Alloy, Lino - Primer, Rem 7 1/2 - Load, Varget 27 gr - Vel, 2000 fps

100 yd, May 2014, ave. of four, five shot groups, 1.395 - June 2014, 100 yd ave. of four, five shot groups 0.774

One very important aspect that hasn't been discused here, is barrel harmonic's and accuracy nodes. Barrel vibrations, displace shots in different positions. The barrel needs to release the bullet in the same position, each shot and unless the harmonics remain the same each shot, there will be a random displacement, regardless of twist.

The accuracy nodes are what you are looking for when you do ladder tests.

Note that of the pictured barrels, used in Larry's tests that the 10 twist barrel is the thinest of the rifles and it looks like it might even have a barrel band. It is also a a 6 groove barrel as opposed to the 4 groove of the others. I would especially call the 10 twist rifle more of a apple than a orange, regarding harmonics.

Frank

108778

[freebullet]

Thanks Larry for sharing the fruits of your labor. Thank you also for not running away when folks seem to get their panties all twisted. Your insight has been helpful in a few of my own projects.

I really like to read about the experiences fro all here and then go test what works for me.

That chrony setup has me a bit intrigued. I see they don't make it anymore. I have been thinking of getting a cheap one to further my loading pursuits but reading of the unit you used in these tests makes me want to spend a lot more $$$$. Do you know of any comparable units in current production that would be of equal quality with pressure estimation capabilities?

[btroj]

Tim, are personal attacks becoming from a mod?

Don't forget that I offered to have you send the rifle in whatever form it was in and send me a bill for services rendered. You refused. Martyrdom isn't very becoming.

[MBTcustom]

I'm not martyring myself. I'm doing what I promised and keeping my end.
I'm merely stating how very disappointed I am with everyone I have talked to on the other side of this argument, and it's a little hard not to feel a little singed to be perfectly frank!

Anyway it was late at night, and I was venting.

[Larry Gibson]

frnkeore

Thought you were done with me......oh well, it had been peaceful in your absence. As usual you base arguments on misunderstandings. Suggest you re-read the parts in the beginnings of this test (Chapter I) where it is explained the accuracy degradation is not compared between barrels but each barrel is compared to itself. The "proportional accuracy" is then compared between barrels. In that comparison we are not looking for "best accuracy" or bench rest accuracy but are looking for that point at which accuracy begins to degrade as we increase velocity.

You are fan of picking out a few examples from CBA matches where the RPM Threshold has been pushed up a bit, just as I've continually said it could be. CBA matches are shot with accuracy in mind BTW and not to push a naked cast bullet of ternary alloy as fast as we can with accuracy (the object of these test....remember?). I suggest you go back to the CBA archives and research the match results going back several years. There you will find (I have researched them as others have) the greatest 99.99% of scores (the few winners and all the losers) are shot with cast bullets with in or well under the RPM threshold. How well does Mr. Bottiger's 7mm BR shoot that bullet at 2100 fps or 2200 fps? Probably not very well or he would be using that. His load is probably exceeding the RPM threshold right in the 2100 fps range which is exactly where many of us have pushed the RPM Threshold up to with 9 - 10" twists.

As goodsteel states; "all I got was that Larry is wrong because Larry is just wrong. No argument that RPM is the force that acts on imbalances (three separate critics admitted this to me over the phone). No evidence to the contrary. No logical reasoning. Nothing but emotionally charged accusations and random information."

Me thinks thou doest protest to much and you perhaps fall in that category. Why don't you prove me wrong by conducting your own tests and present the information/data here in a logical scientific manner instead of random selections from CBA matches of what other shooters do?

You observe; "Note that of the pictured barrels, used in Larry's tests that the 10 twist barrel is the thinest of the rifles and it looks like it might even have a barrel band."

Uh, what barrel band?

Larry Gibson

[Eutectic]

Would like to see how you've managed to "prove" that.
Larry Gibson

Here's your proof Larry. See posts #87 and #88. Then jump up to post #84 (between thread drift) and finally a poster has figured it out. Then one poster, a "Larry Gibson", agrees with him in post #85 !!!!!

Eutectic

http://castboolits.gunloads.com/showthread.php?95248-Borderline-Stabilization-at-long-range/page5

[dtknowles]

Here's your proof Larry. See posts #87 and #88. Then jump up to post #84 (between thread drift) and finally a poster has figured it out. Then one poster, a "Larry Gibson", agrees with him in post #85 !!!!!

Eutectic

http://castboolits.gunloads.com/showthread.php?95248-Borderline-Stabilization-at-long-range/page5

What both you and Mann have demonstrated is consistent with accepted theory. Let us assume that the RPM of the bullet decreases very little in the 75 yards traveled but that the velocity does decrease over that distance then the distance traveled for a single rotation of the bullet also decreased.

Using an example of a bullet fired from a 1/12 inch twist barrel at 2000 ft per second

MV = 2000 FPS
RPM = 120,000 RPM

If the velocity decreases to 1800 FPS at 75 yards but the RPM stays the same then the bullet only travels 10.8 inches per revolution at 75 yards.

120000 rpm divided by 60 is 2000 revs per second. The reciprocal of 2000 rps is .0005 seconds per rev. at 1800 fps that is .9 feet per rev or 10.8 inches per rev.

It is normal and expected that the inches per revolution will decrease the farther the bullet get from the muzzle.

Since the RPM remains the same the stability of the bullet remains the same, the distance travelled per revolution is not the driving factor in bullet stability just the RPM achieved.

Tim

[Larry Gibson]

Thanks Tim, I get what Eutectic was saying now;

"Since the RPM remains the same the stability of the bullet remains the same, the distance travelled per revolution is not the driving factor in bullet stability just the RPM achieved."

The rate of twist part of the equation is established by the twist with the bullet in the barrel in the barrel, not any distance the bullet travels outside the barrel. The measurement of the velocity (while I measure the velocity outside the barrel the M43 Computer, knowing the BC, distance to the start screen and other variables converts the measured velocity back to muzzle velocity. The velocity simply establishes the time element in the equation.

What Eutectic is talking about is the reason why the group dispersion is non linear once the bullet has gone beyond that RPM Threshold. It is most noticeable with the helical arc that increases in a larger diameter as the range increases. It is because the RPM remains constant while the distance traveled is less per the RPM. Essentially as the range increases more RPMs are traveled for the distance traveled which means the helical arc increases in a non linear fashion. Hard to get one's head wrapped around that but once there it makes perfect sense.

Larry Gibson

[Larry Gibson]

Here's your proof Larry. See posts #87 and #88. Then jump up to post #84 (between thread drift) and finally a poster has figured it out. Then one poster, a "Larry Gibson", agrees with him in post #85 !!!!!

Eutectic

http://castboolits.gunloads.com/showthread.php?95248-Borderline-Stabilization-at-long-range/page5

Yup, slept on it over night and it clicked what you were talking about. Then I read dtknowles post and it all came together. Mea culpa on the misunderstanding. Turns out we are definitely on the same page!

Larry Gibson

[dtknowles]

So to maybe expound on Eutectic and Larry's stuff. So if a bullet is not perfectly balanced then every rotation it alters its trajectory (it is really a continuous process but breaking it down into per rotation chunks helps me visualize it) away from ideal. So in traveling to the 100 yard target the bullet rotates 32 times and produces a 1 inch group. If it only rotated 32 more times to get to the 200 yard target we would expect a 2 inch group but it actually it rotates 35 times to get from 100 to 200 yards, I would think that this only opens the group up to 2.2 inches. This was for the 2000 FPS and 120,000 rpm. If we examine 2600 FPS and 156000 rpm I get 32 rev's to 100 and 37 move revs to 200 for a 2.4 or so inch group. I used a BC of .3 which may be a little high so the effect may be more pronounced than this example shows. While it is nonlinear it is not as dramatic of an effect as Larry's experiment shows so something else must be causing the RPM effect other and the compression of the helical path. This has been a very simplified analysis and it attributes all the shot dispersion to the lack of balance of the bullet and nothing to barrel harmonics or velocity or bullet weight variations. If those were accounted for the effect would be reduced.

Tim

[357maximum]

Yup, slept on it over night and it clicked what you were talking about. Then I read dtknowles post and it all came together. Mea culpa on the misunderstanding. Turns out we are definitely on the same page!

Larry Gibson

Well gee darn Larry...NOW if I could just get you to call it the RPM "hurdle" where excellent accuracy with higher rpm gets tougher (not impossible) to achieve.......instead of threshold we too would agree almost entirely. :lol: :drinks:

[garym1a2]

This " helical arc" seems aweful close in speed to the sound barrier, any corralation?

Thanks Tim, I get what Eutectic was saying now;

"Since the RPM remains the same the stability of the bullet remains the same, the distance travelled per revolution is not the driving factor in bullet stability just the RPM achieved."

The rate of twist part of the equation is established by the twist with the bullet in the barrel in the barrel, not any distance the bullet travels outside the barrel. The measurement of the velocity (while I measure the velocity outside the barrel the M43 Computer, knowing the BC, distance to the start screen and other variables converts the measured velocity back to muzzle velocity. The velocity simply establishes the time element in the equation.

What Eutectic is talking about is the reason why the group dispersion is non linear once the bullet has gone beyond that RPM Threshold. It is most noticeable with the helical arc that increases in a larger diameter as the range increases. It is because the RPM remains constant while the distance traveled is less per the RPM. Essentially as the range increases more RPMs are traveled for the distance traveled which means the helical arc increases in a non linear fashion. Hard to get one's head wrapped around that but once there it makes perfect sense.

Larry Gibson

[Larry Gibson]

dtknowles

;2832477]So to maybe expound on Eutectic and Larry's stuff. So if a bullet is not perfectly balanced then every rotation it alters its trajectory (it is really a continuous process but breaking it down into per rotation chunks helps me visualize it) away from ideal. So in traveling to the 100 yard target the bullet rotates 32 times and produces a 1 inch group. If it only rotated 32 more times to get to the 200 yard target we would expect a 2 inch group but it actually it rotates 35 times to get from 100 to 200 yards, I would think that this only opens the group up to 2.2 inches. This was for the 2000 FPS and 120,000 rpm. If we examine 2600 FPS and 156000 rpm I get 32 rev's to 100 and 37 move revs to 200 for a 2.4 or so inch group. I used a BC of .3 which may be a little high so the effect may be more pronounced than this example shows. While it is nonlinear it is not as dramatic of an effect as Larry's experiment shows so something else must be causing the RPM effect other and the compression of the helical path. This has been a very simplified analysis and it attributes all the shot dispersion to the lack of balance of the bullet and nothing to barrel harmonics or velocity or bullet weight variations. If those were accounted for the effect would be reduced.

The above would hold true if every bullet had exactly the same imbalance and exactly the same velocity. We know neither is the case. Additionally your computation is based on the linear expansion of the group + the linear expansion of the deviation. We know that is not correct. No I do not know the formula to figure it out but I'm sure there is one. What we do know is the results on target. The farther from the muzzle the greater effect the centrifugal force has. The helical arc such a bullet takes or the tangent it may go off on (the bullets above the RPM threshold can do that also) does not increase in linear fashion as range increases. Your computations compute what should be happening at 100 and 200 yards but do not take into account the continual centrifugal force on the bullet in between the muzzle and the 200 yard target. The effect is compounded.

Several mention "harmonics" or "barrel harmonics". We all know the barrels vibrate (the "harmonics") as the bullet goes down the bore. We all know that can be the cause of shot dispersion, good or bad. We all know that the shot dispersion should be linear as the range increases. However, can you explain to me and everyone else how the barrel harmonics can cause the bullets flight path to curve in a non linear fashion?

Reducing velocity variation and bullet weight variations are 2 of the ways we produce accurate loads and push the RPM Threshold up. Reducing velocity variation is how we uniform the "barrel harmonics" shot to shot. If you've read any of the additional posts on how I push the 311466 to 2600+ fps with the accuracy shown below you know I get very anal about "bullet weight variations". Don't pay attention to either and the RPM Threshold goes down. Pay very close attention to both and the RPM Threshold goes up. Note the ES/SD on the velocity printout. Not bad for 10 shots at that velocity pushing 40,000 psi with a cast 311466 at 2620 fps (corrected to muzzle). Note the maintained linear expansion of the groups to 300 yards (wind out of 9 o'clock I did not correct for). Go back and review the non linear expansion of the groups posted during the test. No, that non linear expansion is not caused by barrel harmonics or bullet weight variation. Something else happened to those bullets during acceleration. The greater the acceleration the more it happened. What could have it been? Only one thing left; bullet deformation which cause non uniform imbalances to the bullets.

Larry Gibson

108821108822

[Larry Gibson]

Well gee darn Larry...NOW if I could just get you to call it the RPM "hurdle" where excellent accuracy with higher rpm gets tougher (not impossible) to achieve.......instead of threshold we too would agree almost entirely. :lol: :drinks:

Feel free to call it what you want as we agree it is there. I'll buy.

Larry Gibson

[Larry Gibson]

This " helical arc" seems aweful close in speed to the sound barrier, any corralation?

No correlation at all. The bullets are still well above the sound barrier when this occurs. Dropping back down through the sound barrier is another matter entirely. Thanks for the good question.

Larry Gibson

[btroj]

Well gee darn Larry...NOW if I could just get you to call it the RPM "hurdle" where excellent accuracy with higher rpm gets tougher (not impossible) to achieve.......instead of threshold we too would agree almost entirely. :lol: :drinks:

Well said Mike.

I'm not interested in pushing a threshold, I want to leap a hurdle.

[cainttype]

Well gee darn Larry...NOW if I could just get you to call it the RPM "hurdle" where excellent accuracy with higher rpm gets tougher (not impossible) to achieve.......instead of threshold we too would agree almost entirely. :lol: :drinks:


"Just what do we mean by “RPM threshold”. The RPM threshold is that range of RPM where almost all cast bullets will lose accuracy if exceeded. For practical purposes when using a gas checked cast bullet with a BHN of 14-18 the RPM threshold is between 125,000 RPM and 140,000 RPM. But let us remember here that a “threshold is not a ‘limit’."... Larry Gibson, 03-25-2008

Seems to me you've both been agreeing for quite some time.

[btroj]

To Goodsteel.

a few things to ponder about why no solid info from those who may be skeptical.

Leaping the rpm hurdle is no small task in many cases. To quote someone else, it isn't rocket science but it does require some attention to details and some work.

Say a guy decides to try 2 bullets, 5 alloys, and 2 powders. He shoots 4 five shot groups per range session, two each with a couple loads.

That is now 20 different combinations but we need to look at working up a powder charge. Say we try 10 charges with each powder. We are now at 200 combinations, 100 range sessions, and 1000 bullets. I would call this a minimal effort, good results may require more permutations. As we shoot and learn we may alter the original plan.

those bullets need to be cast, heat treated, and aged to get consistent results. That takes time. Lots of time. Some alloys when air cooled may need 3 months of more to settle down.

What is the point of all this? That good, solid testing takes lots of time, bullets, and powder. Those 100 range sessions need to be on days with decent weather. If I can shoot 30 weeks per year with weather that makes for good results, not too windy or hot or freezing, the. I may need a few years to get the results in.

Anyone expecting any sort of solid evidence of anything needs to realize that time is a critical factor. Sound study takes time, a plan, and execution. Shooting a few loads doesn't prove a damn thing.

Who knows, in a few years we may be able to have a good discussion on how to leap the rpm hurdle. We can't do it now because the results aren't in. Heck, I don't even have the bullets cast yet.

Yep, good science is a slow process. It takes dedication, record keeping, and a plan. Anything less is just supposition based on a single result. We also need to keep the absolute bane of science out of the equation- bias. Anyone who has truly studied science knows how easy it is to let bias creep into results. This leads to inappropriate conclusions being drawn.

Now do you see why no data has been posted?

[dtknowles]

dtknowles
The above would hold true if every bullet had exactly the same imbalance and exactly the same velocity. We know neither is the case. Additionally your computation is based on the linear expansion of the group + the linear expansion of the deviation. We know that is not correct. No I do not know the formula to figure it out but I'm sure there is one. What we do know is the results on target. The farther from the muzzle the greater effect the centrifugal force has. The helical arc such a bullet takes or the tangent it may go off on (the bullets above the RPM threshold can do that also) does not increase in linear fashion as range increases. Your computations compute what should be happening at 100 and 200 yards but do not take into account the continual centrifugal force on the bullet in between the muzzle and the 200 yard target. The effect is compounded.

Several mention "harmonics" or "barrel harmonics". We all know the barrels vibrate (the "harmonics") as the bullet goes down the bore. We all know that can be the cause of shot dispersion, good or bad. We all know that the shot dispersion should be linear as the range increases. However, can you explain to me and everyone else how the barrel harmonics can cause the bullets flight path to curve in a non linear fashion?

Reducing velocity variation and bullet weight variations are 2 of the ways we produce accurate loads and push the RPM Threshold up. Reducing velocity variation is how we uniform the "barrel harmonics" shot to shot. If you've read any of the additional posts on how I push the 311466 to 2600+ fps with the accuracy shown below you know I get very anal about "bullet weight variations". Don't pay attention to either and the RPM Threshold goes down. Pay very close attention to both and the RPM Threshold goes up. Note the ES/SD on the velocity printout. Not bad for 10 shots at that velocity pushing 40,000 psi with a cast 311466 at 2620 fps (corrected to muzzle). Note the maintained linear expansion of the groups to 300 yards (wind out of 9 o'clock I did not correct for). Go back and review the non linear expansion of the groups posted during the test. No, that non linear expansion is not caused by barrel harmonics or bullet weight variation. Something else happened to those bullets during acceleration. The greater the acceleration the more it happened. What could have it been? Only one thing left; bullet deformation which cause non uniform imbalances to the bullets.

Larry Gibson


Larry I was just trying show why I think something else must be happening to explain the results you were getting. I do agree it is RPM dependent and you may be on the right track thinking (at least I was getting that impression)it is something happening to the bullets during their spin up in the barrel. It is clear that the bullet weight and velocity variations are well understood and can be limited. The barrel harmonics effect would be linear and not RPM dependent as well so that is not it either. I was looking for an effect that was RPM dependent as the mechanism for the non-linear dispersion. The compression of the helical is just a second order linear effect that when combined with the normal linear dispersion creates a slightly non-linear dispersion but not to the extreme demonstrated in your testing so something else must be happening and it could be damage to the bullets while they are in the bore.

Tim

[357maximum]

Seems to me you've both been agreeing for quite some time.

How astute of you, we have indeed basically agreed for a long long time....Larry just picked terminology that I have disagreed with from the gitgo. I have been trying to get him to call it something other than a "threshold" for years........I guess that makes two stubborn old fools is all....I know from the Pm's that I have shared with Larry that we both would agree for the most part sitting around a well liquored up campfire....he just chooses the wrong words to describe his thoughts and I totally suck at expressing mine in a way that someone smarter than I can understand. :drinks:

[Larry Gibson]

Tim

Sorry if my response came off wrong. It probably got wrapped up with other responses. I was meaning to converse and discuss the issues with you. Yes there are many variables. That's why we look at things from different angles (the different graphs of data) and work diligently to isolate the variables. Your input is appreciated.

Larry Gibson

[Larry Gibson]

How astute of you, we have indeed basically agreed for a long long time....Larry just picked terminology that I have disagreed with from the gitgo. I have been trying to get him to call it something other than a "threshold" for years........I guess that makes two stubborn old fools is all....I know from the Pm's that I have shared with Larry that we both would agree for the most part sitting around a well liquored up campfire....he just chooses the wrong words to describe his thoughts and I totally suck at expressing mine in a way that someone smarter than I can understand. :drinks:

I've no problem's with anyone calling the RPM Threshold a "wall", a "hurdle" or anything else. However, we all know from past posts by 2 or 3 members that they are just waiting for me to change something and then they'd come back criticizing me for it. And to them I say; no I have not changed anything about the basics of the RPM Threshold. I (we) have learned a lot more about the cause and effects of the RPM threshold as we test and study the phenomenon. The more we know the more we add to our ability to crawl over the "wall", "hurdle" over it or "push the RPM Threshold" up. Call it what you want, won't hurt my feelings.

:drinks:

Larry Gibson

[Larry Gibson]

btroj

"We are now at 200 combinations, 100 range sessions, and 1000 bullets."

Yikes! You really know how to make it difficult! I did no where near that many combinations or made that many range trips. Probably gone through that many bullets though. I've worked with 3 rifles, 5 bullets, 4 alloys and 5 powders. It didn't take 200 combinations and even 50 range sessions to get to where I am. I am willing to help, no sense reinventing the wheel?

Larry Gibson

[357maximum]

I feel your pain Larry..truly I do....you are not wrong on the "I told you so" bunch.

I have just seen the HURDLE :drinks: cleared too many times by a few select shooters around here to call it a wall or a threshold into some other dimension. Not 3 weekends ago I watched as a fellow member blasted the hurdle with an as issued 1903 Springfield and also watched another member go smack over the hurdle with an as issued M1 Garand. The Springer load was actually outdenting military j-word tracers on mild steel at 250 yards and doing it with about MOA accuracy with the issue sights. The hurdle can be cleared sometimes by a little and sometimes by alot...all it takes is alot of work/playing/load/alloy development......I have done it too but mine was based more on others hard work/ sheer luck/pattern recognition than it was on hard diligent work on my part.

[dtknowles]

Larry

You did not upset me I responded to make clearer from where I was coming. I don't expect that anyone still makes gain twist barrels. The only gun I know that used one was the 6.5 Carcano but that might be another way to push up the RPM threshold. Using more twist than required for a given bullet weight will make it harder to get the best accuracy but maybe spinning the bullet up more gradually would help too.

Tim

[dtknowles]

I feel your pain Larry..truly I do....you are not wrong on the "I told you so" bunch.

I have just seen the HURDLE :drinks: cleared too many times by a few select shooters around here to call it a wall or a threshold into some other dimension. Not 3 weekends ago I watched as a fellow member blasted the hurdle with an as issued 1903 Springfield and also watched another member go smack over the hurdle with an as issued M1 Garand. The Springer load was actually outdenting military j-word tracers on mild steel at 250 yards and doing it with about MOA accuracy with the issue sights. The hurdle can be cleared sometimes by a little and sometimes by alot...all it takes is alot of work/playing/load/alloy development......I have done it too but mine was based more on others hard work/ sheer luck/pattern recognition than it was on hard diligent work on my part.

It would be nice to know what the load the Springfield shooter was using, you said fellow member, do you mean a member here, couldn't we get him to share his work. I have a Ruger M77 in 30-06 that is definitely not shooting MOA.

Tim

[357maximum]

Tim

It was Dutch4122 that put that sweet shooting combo together.....he does not post here much....too busy doing things to talk about things I guess. I just let him know about this thread and he will be along with the particulars when he gets a ROUNDTOIT.

[freebullet]

I want to go down around the wall crossover the threshold and leap the hurdle in the next room. It's all the same thing, yet almost a page about it. Wow
Calling it a wall or hurdle would be referring to it as more of a limit than calling it a threshold.

I would rather hear more about the chrono than what to call the rpm thresallurdle.

[357maximum]

Freebullet...semantics....some of us have been arguing about them for years......you trying to ruin our fun? :lol:

[btroj]

If it weren't for semantics we would all agree and that would make for a boring forum.

Sometimes those little differences make all the difference in the world

[MBTcustom]

To Goodsteel.

a few things to ponder about why no solid info from those who may be skeptical.

Leaping the rpm hurdle is no small task in many cases. To quote someone else, it isn't rocket science but it does require some attention to details and some work.

Say a guy decides to try 2 bullets, 5 alloys, and 2 powders. He shoots 4 five shot groups per range session, two each with a couple loads.

That is now 20 different combinations but we need to look at working up a powder charge. Say we try 10 charges with each powder. We are now at 200 combinations, 100 range sessions, and 1000 bullets. I would call this a minimal effort, good results may require more permutations. As we shoot and learn we may alter the original plan.

those bullets need to be cast, heat treated, and aged to get consistent results. That takes time. Lots of time. Some alloys when air cooled may need 3 months of more to settle down.

What is the point of all this? That good, solid testing takes lots of time, bullets, and powder. Those 100 range sessions need to be on days with decent weather. If I can shoot 30 weeks per year with weather that makes for good results, not too windy or hot or freezing, the. I may need a few years to get the results in.

Anyone expecting any sort of solid evidence of anything needs to realize that time is a critical factor. Sound study takes time, a plan, and execution. Shooting a few loads doesn't prove a damn thing.

Who knows, in a few years we may be able to have a good discussion on how to leap the rpm hurdle. We can't do it now because the results aren't in. Heck, I don't even have the bullets cast yet.

Yep, good science is a slow process. It takes dedication, record keeping, and a plan. Anything less is just supposition based on a single result. We also need to keep the absolute bane of science out of the equation- bias. Anyone who has truly studied science knows how easy it is to let bias creep into results. This leads to inappropriate conclusions being drawn.

Now do you see why no data has been posted?

Brad,
That is the closest thing to a real post I have seen you make in some time. I agree with you wholeheartedly, right up to your concluding question.
The claims that this is able to be done by anyone, at significantly less effort than just handing your rifle to a gunsmith, breaking off a few C notes, and enjoying high-"ish" FPS, leads me to believe that it must not be as hard as all that.
Of course, if in reality, if this "perfect storm" is as you say (and I find much more likely) is very difficult to attain, and will cost you more in time, bullet molds, and components/brass, than any custom rifle build, then it boils down to which is capable of more accuracy.
Say the goal is 2800FPS with MOA accuracy so as to allow engagement of targets out to nearly 1000 yards.
One method that has been claimed add nausium, is to make the 1000 yard crawl over broken glass, via the flaming hoops of fire, and traversing the crocodile laden river of acid, till you arrive at a place where sweet fruition is realized with any janky old mil-surp with any twist.
Got it. I love the idea.
Larry is just offering a much more reasonable alternative to achieving that goal:
Spend a few hundred bucks and have your rifle rebarreled to a slower twist and do what Larry is suggesting in this thread. No ten years throwing powder primers, lead, money and time down the toilet like it was free. No butt kissing extraordinaire. No standing on someone else's experience (that cannot conceive of, or allow a less expensive option). Just use what you've got and rock on, under the RPMTH.

Personally, I want to do both, and I'll settle on whichever one is more accurate. Since Larry asks nothing and gives information freely (like what rifle, what range, pictures of real groups (and different groups at that. Not different pictures of the same group. "Ahem") graphs, clear explanations, and unbiased references that are taken in context.)I'm going to go this way for now.
Larry's method is so well written and laid out, It won't take me (or anyone with any rifle) long to put it into practice, and experience what is capable from my bench.
It's cheap, effective, and anyone who can read can git-er-did pronto.

By the same token though, I have not disregarded what I have been told might be possible if I am well healed enough in time money, components and patience.
Unfortunately, certain people have been swearing to high heaven and low hell that this can be done in any rifle since the mid 2000's, yet have not produced a clear argument in public in that entire time. You would certainly think that all that effort would be based on something but sadly, any sort of convincing argument to the contrary (sorry, trolling, vague allusions, carrots on a stick, rabbit trails, and hatred don't count, and would not be accepted by anyone of higher learning or education) have not been forthcoming.

So regarding your final question, I certainly do not see how in ten years, none of the people who argue so vehemently against the simple, cheap and effective method that Larry has laid out here have managed to produce a single thread or post that comes even close the level of professional communication that Larry has demonstrated here. It's truly a mystery.
Even if one decent irrefutable group had been shot and posted over and over and over, it wouldbe something but there is nothing of the sort.
Strange!

[btroj]

Why do that which is easy? That doesn't teach us anything. It doesn't further the knowledge. It doesn't fulfill a basic human inquisitiveness to learn.

I would rather fail trying the difficult that stick with the easy.

I always told my daughter that accomplishing the easy isn't very rewarding because it is easy. It is in accomplishing the difficult that we learn about ourself.

From what Larry is saying anyone can shoot well with a 16 twist barrel but it takes a truly accomplished caster and shooter to do so with a 12 twist.

Which do YOU want to be? I know what I want and it certainly isn't to take the easy way out.

[btroj]

As for those who say it is possible they have posted here. People just refuse to believe them. Well, some people do.

Just because you haven't seen it with your own eyes doesn't mean it isn't possible.

[MBTcustom]

Why do that which is easy? That doesn't teach us anything. It doesn't further the knowledge. It doesn't fulfill a basic human inquisitiveness to learn.

I would rather fail trying the difficult that stick with the easy.

I always told my daughter that accomplishing the easy isn't very rewarding because it is easy. It is in accomplishing the difficult that we learn about ourself.

From what Larry is saying anyone can shoot well with a 16 twist barrel but it takes a truly accomplished caster and shooter to do so with a 12 twist.

Which do YOU want to be? I know what I want and it certainly isn't to take the easy way out.


Because people have lives that don't revolve around shooting. Because people have limited money with which to buy components, and the prospect of just blowing what they have in order to find something that might be there is not an option, especially when they have an option right in front of them that will work just great for much less outlay (you know: so they can get back to actually shooting groups).
Because people have limited time such that one range trip every two weeks without fail is pushing it.

Which do I want to be? I want to be the guy that shoots tiny groups at long range with cast, and I really don't care how I get there as long as I can do it while I'm still young. LOL!
That's the object here. If you really believe what you are saying, then I expect you drive a horse drawn buggy to work everyday yes? LOL!
That's the way I see shooting high velocity the other way. I want to do it, but it's for the novelty of knowing how. Seeing as how I get all my gunsmithing done for free it really makes waaaaaaaaaayyyyyy more sense for me to go with slower twist wouldn't you say? Double whammy! It's cheap and then it's cheaper!

[bnelson06]

Because people have lives that don't revolve around shooting. Because people have limited money with which t obuy components!

I say we start a collection and I can devote all my time to this quest. A few dollars from many goes a long way for one :)

[MBTcustom]

As for those who say it is possible they have posted here. People just refuse to believe them. Well, some people do.

Just because you haven't seen it with your own eyes doesn't mean it isn't possible.

Whatever. Heard that lament for months now, and I wouldn't' say they strained themselves. If they had put one tenth the effort into helping people with their point of view that Larry has, they wouldn't be so dangerously close to taking their "secrets" to the grave with them.
More people would believe them if they'd quit fighting all the time and post about what they are doing, instead of running off the people who do believe in them and want to learn (such as myself).
They sure have posted here though. You just have to eat the meat and spit out the bones. Never mind the fact that you have to dig through 25 trash barrels full of bones before you find a stale half eaten Twinky.
I have never said it was impossible. I believe it is. I said it was impossible for the people who claim to be capable of it to find the little button that operates the shutter, or climb out of the trenches and have a little fun teaching people instead of fighting with them in open forum.
It's not about believing in them or not. It's about getting them to teach instead of troll that's the real trick.
Look at the lengths Larry has gone to to explain his point of view in spite of all the trolling. He's kept at it in spite of all the naysayers and guess what? People are catching on! Had the people on the other side not been wasting their time trying to undermine any alternative viewpoint, they might have actually gained some ground on this forum. As it is, if they endure just one fraction of what Larry has had to, they fold up their kite and sulk off.
I really don't know what to say about that, but if you want to lose my respect, that's certainly one of the best ways.

[cainttype]

A firearm is a tool. It's as simple as that.
Knowing how to accomplish the task at hand with an inferior tool is never a bad thing. Knowing the best tool for the task is pretty high on the priority list, too. Using the best tool available for accomplishing the same task is just good common sense.
If HV using cast, while maintaing accuracy, is easier to achieve by using a slower twist...Where's the problem?
It would seem to me that anyone wanting to "learn" as much as he can about shooting cast at high velocity would consider that information as critical knowledge, even if they know it can be done with more difficulty using a less than optimal "tool".

[357maximum]

Because people have lives that don't revolve around shooting.

Preposterous and I do not believe it for a minute.....BS...liar liar. :lol:

Most of what you seek was posted here: http://castboolits.gunloads.com/showthread.php?238815-Making-the-most-of-a-good-rifle , just do not look for Larry style, take you by the hand and show you methods, not only are some unwilling to do such things...some people are simply not born with the ability to teach the way Larry does......believe it ...for it's true. Not everyone was born a teacher...accept that fact and do some work on your own.....the basic blueprint is there waiting for you, and there are several ways to skin a cat........accepting that a cat cannot be skinned in less than 5 minutes is not the way to a fur coat made by your own hands...,...... you could just go to the store and buy a coat too...always an option...your call/your money/your time/your goals. To each their own, but calling others names for taking a different approach...solves what exactly......not everyone comes here to gain notariaty or to teach a certain method to reach mediocracy...and no that was not a slam on Larry....to each to their own desires.


BTW.....I would have piotentially flagged a few of your posts in this thread when I was a mod...please lighten up Tim, this is nothing to pop a vessel over.....your best way to go fast may very well be to re-barrel to a slower twist....it is a good option....a certain one....some people do not like easy/certain....to each their own....you pays your money not I...so do what YOU want, but please do not so believing it is theee only way.


sincerely,
Mike

[freebullet]

so can i shoot a gas checked boolit without the gas check or not?

[frnkeore]

Larry says,


Thought you were done with me......oh well, it had been peaceful in your absence.

No larry, It was you that said that you were done with me, in one of our past discussions. I said that I did not want you to leave the thread and ask that you stay and follow it through. You can look it up if you like.


You are fan of picking out a few examples from CBA matches where the RPM Threshold has been pushed up a bit, just as I've continually said it could be. CBA matches are shot with accuracy in mind BTW and not to push a naked cast bullet of ternary alloy as fast as we can with accuracy (the object of these test....remember?).


Match shooters are looking for the best accuracy that they can generate, no matter what RPM it is. They are ALSO looking for the highest velocity they can obtain, while doing so, to reduce wind drift as much as possible. It can go hand and hand.

You'll note that 90% of the HV shooters are using medium burning rate powers, just as the jacketed shooters are using.

For your "threshold" to hold up, at all, it needs to be with any powder, including Unique. Other wise, RPM is just one factor of MANY and that IS, all it is!

Your term "threshold" seem conveniant to me. I see so many times that you try to turn people away from 2000 fps loads in a 10 twist and use loads in the 1600 - 1800 fps range because 2000 fps is not in your "threshold". I say give them the oppertunity to try it and give them the best info you can to get them there.

Then you tell people like me that it's just "threshold" and it can be pushed up when I/we have conflicting factual results, trying to minimize the conflicting info. It's kinda like your trying to "have your cake and eat, too".

It sounds to me that you use it more as a limit because you're not able to exceed it and don't know what it takes to do so.

While I will agree with the others that you put in a lot of work doing your test and it might prove that each rifle has a level of accuracy with the given powder and bullets that you fed them. It doesn't prove that the 10 twist, isn't as accurate as the others at any given RPM. I really couldn't call it scientific at all. It would have to be a blind test, with the same rifle, same chamber, same barrel weight & lenght, with different twist barrels. Even so, it can't test HV w/o the proper chamber and throat design. If you know anything about testing, you know that the tester can make his preceived out come a reality and not relalize it, himself.

The following are more match results for fast twist HV rifles. As you know, the shooters use these loads as there best and can go even higher (how high, I can't say) with better than average accuracy, they aren't looking for a "threshold" or hunting accuracy, just the best they can get, if it happens above the "threshold" so be it!

That said, I can tell you the basic reason that the following shooters can do what they are doing. It's in the chamber and throating first, next, the use of linotype for bullets and their fit, powder and other things come as tuning ingrediants. Note the alloy, most match winners and records are set with linotype.

Standard chambers, just won't cut it! The neck, freebore and leade angle are paramount when it comes to accurate cast bullet shooting, whether it's slow, medium or HV.

In closing, let me say again......... If one person can do something, reliably, then ANY other person can do that same thing! This is not magic, it's knowing how to put the whole package together.

Tamaqua, PA

Bottiger, Jerry, Cartidge, 7mm BR - Barrel, Shilen 23" lg, 9 twist - Weight, 12.62 lb - Scope, Weaver 36x

Bullet, NEI 170, Nose .276, Band .285 - Alloy, Lino - Primer, Rem 7 1/2 - Load, Varget 27 gr - Vel, 2000 fps (160,000 RPM)

100 yd, May 2014, ave. four, five shot groups, 1.395 - June 2014, 100 yd ave. of four, five shot groups 0.774

Bottiger, Jerry HVY 196 7x, Nesika Shilen 1 deg. Weaver 12 Lb. NEI 170 L Lino- nose .276, band .285 - 27.0 gr Varget - 7 1/2 Rem - 2000 vel


May, 2014 Charlotte, NC


Galindo, Adolph, Class, UnP - Cartridge 30BR - Barrel, Lilja 22" lg, 8 twist
Scope, Leupold 40x - Weight, 22Lb. - Bullet, LBT 180 sp - Alloy, Lino - Nose .304, Base .310
Primer, Fed 205m - Powder Chg, 28.5, Varget - Vel 2100 (189,000 RPM)

Galindo, Adolph UnP 197 8x 100 yd, 193 2x 200 yd, 100/200 Agg 390 10x

Galindo, AdolphUnP 5 shot group, 0.469 100 yd, 200 yd,1.807 100/200 MOA 0.686

Galindo, AdolphUnP 10 shot group, 0.951 100 yd, 3.232 200 yd, 100/200 MOA 1.283


Lowther, Scott, Class HVY - Cartridge, 30 BR - Barrel, Lilja, 24" lg, 10 twist
Scope, Leupold 36x - Weight, 13.5 lb - Bullet, Accurate 311205 - Alloy, Lino - Nose .3005, Base .311
Primer, Fed 205m - Powder chg, 28.3 N133 - Vel 2100 (151,200 RPM)

5 shot groups (ave of four, five shot groups) 0.759, 100 yd, 1.532, 200 yd, 0.763, Combined MOA

10 shot groups (ave of two 10 shot groups) 1.587, 100 yd, 3.633, 200 yd, 1.699, Combined MOA

Lowther, Scott, Class, Production - Cartridge, 308 Win - Barrel, Savage 26" lg, 10 twist
Scope, Weaver 36x - Weight, 11.75 lb - Bullet, Accurate 310220 - Alloy, Lino - Nose .300, Base .310
Primer, Fed 210m - Powder chg, 27.5 N130 - Vel, 2000 (144,000 RPM)

5 shot groups (ave of four, five shot groups) 1.321, 100 yd, 200 yd 3.081, 1.431 Combined MOA

10 shot groups (ave of two, ten shot groups) 3.242, 100 yd, 200 yd, 4.322, 2.701 Combined MOA

[357maximum]

so can i shoot a gas checked boolit without the gas check or not?


Has Carpetman been re-born???...RAY IS THAT YOU, boy you have been missed round here, got any spare gubmint cheese to share?

Yes you can shoot a gaschecked boolit without the check, but the world will go off it's axis and spin us all into space, destroying the atmoshere/stratosphere and then the sun will scroch the Earth into a Mars like landscape....do not do it please....we all need atmosphere.

[freebullet]

I'm doin it lol.

My name is Bruce and I do play with carpets.

[357maximum]

Bummer but I guess it all had to end sooner or later...oh well, maybe I can say hey to Ray in the spin cycle. :drinks:

[Dutch4122]

357maximum is way to kind.[smilie=s:

My rifle is a CMP Greek return Remington made 03A3 produced in May, 1943; with a brand new (in the wrapper & cosmo'd when I bought it) Remington made July of 1943 two groove replacement barrel. Barrel was installed by Badgeredd. As of this date the barrel has had only 103 rounds fired through it of the following load and no other:

Bullet Design: RCBS 30-180-SP (Late version, bore riding nose)
Actual weight lubed & checked: 190 grains

Cast of an alloy that is: (according to Badgeredd's alloy calculator)

92.35% Pure lead and other trace elements
3.73% Tin
3.5% Antimony
.22% Copper
.20% Arsenic

(Note: This is a copper enhanced alloy, and not the type of alloy that the OP used in the testing he has presented in this thread)

The easy way to mix this alloy is to follow this simple recipe of 8 lbs. Clip On Wheel Weights, 1.5 lbs. of Pure Lead, and .375 lbs. of Rotometals Grade 11 Babbit for a 10 pound pot. Double the amounts for a 20 pound pot and quadruple the amounts for a 40 pound pot, etc. Here's a hint, don't assume that your soft range scrap is in fact pure lead that's ok to use in this mix, it probably isn't. Use what this recipe calls for, don't deviate. There are enough variables to deal with in Clip On Wheel Weight alloy as it is. No need to have the other components skewed.

Bullets were water dropped from the mold into a five gallon water bucket. They were allowed to stabilize for two weeks, BHN was 28, sized/checked to .310" diameter and lubed with MML + 5% Soap. My mold casts a bullet nose that is .302" diameter using the above alloy from my mold.

The load itself is as follows: (loaded and shot as projected in Quickload)

46 grains of IMR-3031

CCI #200 Large Rifle Primer

54,000 psi / 100% powder burn / muzzle pressure = 7,849 psi

5 shot average over the chronograph is 2,510 fps. I was hoping to match the U.S. MkI ball load which was a 175 grn FMJ Spitzer at 2,600 fps. However, given the accuracy potential this load is showing I'm not going to quibble over 90 fps, especially since my boolit is 15 grains heavier.

Ok, so here's the deal with this rifle and load. When I say 103 rounds I mean that is the absolute total number of rounds which have ever gone down this barrel, period. The barrel has only ever fired this particular load. The 1st round went down the tube at the end of May. First 5 shots fired went into 3" at 100 yards with one flier I believe to be the very first shot opening the group from 2.5" to 3" Either way, that is within acceptable U.S. Ordinance accuracy standards for these rifles as they came off the line at any manufacturer. I was shooting that day with Castboolits Member "Mostlyonthepaper" and he can verify this plus I have the target saved. Minor sight adjustments were made and after that the rifle has not been put through any serious target work since; just pounding rocks and steel at 250 yards. The plan has been to give it about these 100 rounds of shooting for the bore to season with lube before getting serious on paper. While shooting at Badgeredd's place on June 8th the rifle seemed to be shooting better as the round count rose. 357maximum was spotting for me through 10x binoculars and advised I was hitting the same 2"-3" spot on a rock @250 yards repeatedly before I split the thing.

So, the load shows some real promise out of a 24" barreled 03A3 with issue receiver sights. Enough to warrant some real testing.

dtknowles -

Right off the bat I will tell you this. Bullet fit is king. Also, my rifle has a 24" barrel and yours has a 22" barrel. I believe, based on my experience, that keeping muzzle pressures below 8,000 psi is very important for even usable accuracy. Your barrel will produce higher muzzle pressures than mine with the same load due to the fact that it is shorter. Find a bullet in the 200-210 grain weight range when cast out of this alloy that fits your rifle properly when chambered. Start out at 43 grains of 3031 and work up. If you have the alloy, lube, and fit right I think you could find a good load.

[btroj]

Well, that answers that. Thanks Dutch and Mike.

Tim, you need to listen to Mike. You are way too worked up over this. Some don't post here because they don't want to. That doesn't make them evil, they just may not care. Just because a person doesn't share everything doesn't make what they did impossible or unachievable. Like Mike said, not everyone is a teacher. We also know a few aren't good at spoon feeding people.

The info is out there. Do the research. Learn.

Yes, a poorly balanced bullet will be affected by higher rpm. Any spinning load requires better balancing as the rpm goes up. A washing machine, tire, centrifuge, lathe, or whatever. The answer lies not in limiting how fast we spin things, it lies in how to better balance the load we are spinning.


We choose to go to the moon. We choose to go to the moon in this decade and do the other things, not because they are easy, but because they are hard, because that goal will serve to organize and measure the best of our energies and skills, because that challenge is one that we are willing to accept, one we are unwilling to postpone, and one which we intend to win, and the others, too.

I wasn't alive for this speech Tim. Neither were you but let it be your guide. Don't do this because it is easy, do it because it is difficult. Doing the difficult things in life are what give us meaning. The difficult things are what give us purpose, they are the things that make us learn, grow, and push the envelope.

larry has given us a hurdle. It is now up to each of us to decide if we see a hurdle or a barrier. We can either learn to leap over it or we can be held back because of it.

[MBTcustom]

Your right, I am worked up over this because it's tearing down my favorite forum.
I never said anything was impossible or unachievable. I have a lot of faith in the human spirit and our ability to understand science, but I also realize that in any setting, you can spend years getting nowhere (like we have on this issue) if your research is based more on disproving someone else's research and fighting over who's righter, than pushing for your own viewpoint and then trying to see where it fits in the puzzle.

I'm only trying to help people to see the foolishness of fighting over different points of view, and trying to ram them into the same bottle.
There will come a day that we can take an all encompassing look at the HS castboolit issue, but for the moment, we need to divide and concur.

Its like looking into a dark place and trying to see the landscape in front of you. Larry illuminated a very specific piece of that landscape and instead of everybody shining their flashlight at different spots so that we might get a whole picture, lots of effort has been expended to snuff out his light because it doesn't encompass the whole panorama.

Dutch, thank you for that amazing post, but I wish it was a thread instead of a post in the middle of an RPMTH discussion.

To the rest of you, please, if you disagree with the OP, go start your own threads on what your research is telling you and leave this viewpoint out of it, and stay out of this discussion. I will defend your viewpoint from being attacked, squelched, subverted, or destroyed with the same fervor, but not if your whole basis for research is to disprove something that someone else has done. That's not science. That's using something that looks like science as a weapon to beat people over the head with. If your research is based on your rifles and your point of view, and is honestly looking for truth (like this thread started, then I want to hear everything you have to say, and so do a lot of other people.

If everybody did this, then I think we would get where we are trying to go much faster and happier.

[btroj]

Rpm arguing, disagreement, and the like isn't what is tearing down this forum. That is an entirely different problem, call it forum evolution.

larry and others have been arguing over this for a decade or more. This is hardly a new battle.

Any time you get people who are deeply engaged in an activity there will be heated disputes. Thinking people often don't agree. If they do then someone isn't thinking.

A constant focus on the issues that separate us is far more divisive than the issue itself. Is the fact others insist I agree with the theory any worse than my refusal to do so? Singling out naysayers as trolling leprechauns doesn't do anything to solve the problem does it?

[Newtire]

I'm glad to see that the arguments about spelling and other unrelated nit-picking has come to a halt and things have gotten more civil and to the point of the topic. Somehow, I keep seeing how a spinning top acts as it slows down and begins it's "death wobble" just before it finally starts walking all over the floor and crashes into the nearest wall. It helps me understand that there seems to be a certain point where it loses stability but it never regains it once it begins that wobble and is slowing down. I couldn't explain it but know it happens because I can see it. That's what I like about this experiment, the results are visible.

[Eutectic]

We choose to go to the moon. We choose to go to the moon in this decade and do the other things, not because they are easy, but because they are hard, because that goal will serve to organize and measure the best of our energies and skills, because that challenge is one that we are willing to accept, one we are unwilling to postpone, and one which we intend to win, and the others, too.

I wasn't alive for this speech Tim. Neither were you but let it be your guide. Don't do this because it is easy, do it because it is difficult. Doing the difficult things in life are what give us meaning. The difficult things are what give us purpose, they are the things that make us learn, grow, and push the envelope.

larry has given us a hurdle. It is now up to each of us to decide if we see a hurdle or a barrier. We can either learn to leap over it or we can be held back because of it.

Great post Brad! Thank you for it!

I want to share a couple thoughts.....

WW2 was just over and I was in grade school. I was already a shooting 'nut' and already casting boolits! Under the strict eye of my father I might add. We shot with a guy I'll call 'Benny' ... Even as a kid I saw his arrogance and opinionated nature. My father like him and I listened to their conversations quietly and learned.
A few years later I went to work for a company that 'Benny' worked for as well. It those days companies had enough talent on board to train their employees in a college like atmosphere.... 'Benny' taught me metallurgy... He was the most arrogant person I had ever met at that time of my younger life. But he knew metal! Did he ever! He is now still, the smartest man on metallurgy I have ever known. 'Benny' has been dead for many years now.... a sad part of growing old. But he left me with a philosophy about life... one worth sharing.... "One should tolerate extreme arrogance if vast knowledge is being offered.... Yet extreme arrogance without knowledge can sound like a clanging bell!"

A gathering of vast knowledge such as we have on 'Cast Boolits' could be compared to a piece of hardened steel. It is strong and it won't bend! When you work to reshape it, you need to grind it... When you do sparks will fly! That's just how it is! You don't anneal the piece to more easily shape it without sparks..... IT MAY NEVER BE THE SAME AGAIN! (Attn: Mods)

I have supervised many brilliant people over the years... Brilliant people don't like to be micro-managed.. I've found it better to 'drop' a few hints and then let them 'take root' in their own brilliant mind... You see, people can't (or won't) tolerate a 'Benny' anymore.... It's sad for an old guy to see...

This site to survive, cannot be turned into a flock of sheep. Shepards are needed. The best of sheep will fail without them.
Moderators...... Let the sparks fly within reason! Political correctness has run amok in these times and shouldn't be the primary concern here at 'Cast Boolits' for us to survive. Some of my best friends have ground sparks from me and visa-versa......

You see, I did hear the speech Brad related to. In fact I was married and had a child. Old people have a wealth of knowledge even if their delivery is sometimes misunderstood.

Eutectic

[Larry Gibson]

Dutche4122's post settles what?

What you see in his post is exactly what I say can be done; push the RPM threshold up. He has used a good rifle with a good bullet cast of a non- ternary alloy. He has strengthened that bullet over the Ternary alloy......get it!

357amximum says in his post Dutch's accuracy was "about moa". Dutch says it is a documented 2.5 - 3 moa based on an actual target with only one load and only with a single 5 shot group. How many of you have gone out one day and shot the proverbial "eureka" very small group with a load, gone home and loaded up some more and then found out they really shot into much larger groups? I dare say all of you have. One 5 shot group is a very poor indication of actual accuracy potential.

I've also watched a lot of rocks and other things get shot at through binoculars and spotting scopes upwards of 25+ power. What we "think" is 2 -3" most often is a lot larger. How many shots hit the rock? Did any miss? In this case it was 'thought" the load to be "about" moa capable when, with insufficient sample size, it might have been, on an actual target, 2.5 to 3moa capable....maybe. Bit of a discrepancy in what was "thought"? We need to have sufficient data such as targets at sufficient ranges shot with sufficient shot groups to "settle" this. What we "thought" just doesn't settle anything.

I've no problem with Dutch's report, he is telling it as it was. But are we making assumptions based on insufficient data/results? Too many times we have made erroneous conclusions based on insufficient data. Until Dutch puts that load on paper at 100, 200 and perhaps even 300 yards with 10 shot groups we really won't know and neither will he.

So, btroj, what Dutch's post really "settles" is one way to push the RPM threshold up; harden the bullets by adding babbitt and heat treat/WQ. That is just as I have said many, many times as one way to push the RPM Threshold. But still, we don't know if Dutch's load really pushed the RPM Threshold simply because Dutch's test was not conclusive based on sufficient data. You went to great lengths explaining how you'd need a 100+ trips to the range, 200+ load combinations and 1000+ bullets to figure it out. But now you say Dutch with one inconclusive five shot group with one load, with just over 100 rounds (only 5 put on target) and then busting rocks with the rest "settles it"? Are you serious?

Look at the target below that has exceeded the RPM threshold by as much as Dutch's load. The 311291 was cast of the ternary alloy and was pushed at 2515 fps by 4895. Note out of 10 shots which gives the real picture of the accuracy potential there are 5 shots within 4" of each other at 200 yards. Those certainly would have been rock bustin' shots with a sight adjust too, wouldn't they? If I had only shot those 5 shots I might have come to the erroneous conclusion the RPM threshold was bunk too. With sufficient data (sample size of 10 shots) the truth emerges as we see the actual accuracy potential of 14.5" at 200 yards. I can show you many examples BTW including a MP 30-180 at 2509 fps cast of the same alloy as Dutch used. There were 6 of the 10 shots in that target which went into 3.5" at 200 yards. Problem was the other 4 shots stretched the actually accuracy to 11.5" for the sufficient sample group of 10 shots. That was out of my 10" twist '06 test rifle BTW. You might study "random selection" and "random dispersion" to understand why a sufficient sample size is necessary for surety of a conclusion. Surety of conclusion trumps "what we thought" every time.

Again, I have no problem with Dutch's post. It is quite interesting, informative and at least contains details on what he has actually done (not what someone else has done, especially as taken of match results where we really don't know the details). Realizing that the 2.5 - 3 assumed moa may be "acceptable U.S. Ordinance accuracy standards" at 100 yards but in the case with HV cast bullets does it hold that accuracy potential as the range increases? It may indeed prove very interesting if he can follow up with 10 shot groups at 100, 200 and 300 yards? Is the group expansion going to be linear of non linear? The answer found there would "settle it".

Larry Gibson

108885

[Newtire]

An experiment like this one could take forever if you really think about it. It does work if everyone puts in a little bit of factual stuff. It's all useful as long as it's based on fact. Thanks again Larry and all you other guys with facts to share.

Now, we need someone to start a thread on rifles using gain-twist. I always thought that would be the way to go with cast. Only one I can think of that used gain-twist, aside from a few muzzle-loaders was the Carcano. It's gotta be someone with more money than I have!

[dtknowles]

357maximum is way to kind.[smilie=s:

My rifle is a CMP Greek return Remington made 03A3 produced in May, 1943; with a brand new (in the wrapper & cosmo'd when I bought it) Remington made July of 1943 two groove replacement barrel. Barrel was installed by Badgeredd. As of this date the barrel has had only 103 rounds fired through it of the following load and no other:

Bullet Design: RCBS 30-180-SP (Late version, bore riding nose)
Actual weight lubed & checked: 190 grains

Cast of an alloy that is: (according to Badgeredd's alloy calculator)

92.35% Pure lead and other trace elements
3.73% Tin
3.5% Antimony
.22% Copper
.20% Arsenic

(Note: This is a copper enhanced alloy, and not the type of alloy that the OP used in the testing he has presented in this thread)

.........Bullets were water dropped from the mold into a five gallon water bucket. They were allowed to stabilize for two weeks, BHN was 28, sized/checked to .310" diameter and lubed with MML + 5% Soap. My mold casts a bullet nose that is .302" diameter using the above alloy from my mold.

The load itself is as follows: (loaded and shot as projected in Quickload)

46 grains of IMR-3031

CCI #200 Large Rifle Primer

54,000 psi / 100% powder burn / muzzle pressure = 7,849 psi

5 shot average over the chronograph is 2,510 fps. I was hoping to match the U.S. MkI ball load which was a 175 grn FMJ Spitzer at 2,600 fps. However, given the accuracy potential this load is showing I'm not going to quibble over 90 fps, especially since my boolit is 15 grains heavier..........dtknowles -

Right off the bat I will tell you this. Bullet fit is king. Also, my rifle has a 24" barrel and yours has a 22" barrel. I believe, based on my experience, that keeping muzzle pressures below 8,000 psi is very important for even usable accuracy. Your barrel will produce higher muzzle pressures than mine with the same load due to the fact that it is shorter. Find a bullet in the 200-210 grain weight range when cast out of this alloy that fits your rifle properly when chambered. Start out at 43 grains of 3031 and work up. If you have the alloy, lube, and fit right I think you could find a good load.

Thanks Matt

This looks like something I could use. I might try this alloy in my 30 BR. too.

Tim

[dtknowles]

........... Standard chambers, just won't cut it! The neck, freebore and leade angle are paramount when it comes to accurate cast bullet shooting, whether it's slow, medium or HV.

In closing, let me say again......... If one person can do something, reliably, then ANY other person can do that same thing! This is not magic, it's knowing how to put the whole package together.

May, 2014 Charlotte, NC

Galindo, Adolph, Class, UnP - Cartridge 30BR - Barrel, Lilja 22" lg, 8 twist
Scope, Leupold 40x - Weight, 22Lb. - Bullet, LBT 180 sp - Alloy, Lino - Nose .304, Base .310
Primer, Fed 205m - Powder Chg, 28.5, Varget - Vel 2100 (189,000 RPM)

Galindo, Adolph UnP 197 8x 100 yd, 193 2x 200 yd, 100/200 Agg 390 10x

Galindo, AdolphUnP 5 shot group, 0.469 100 yd, 200 yd,1.807 100/200 MOA 0.686

Galindo, AdolphUnP 10 shot group, 0.951 100 yd, 3.232 200 yd, 100/200 MOA 1.283



While all the examples are very good shooting, better than any that I have shot with cast bullets none of them are over 2200 fps and the point of this thread is to get higher velocity. Only one was over the 160,000 RPM which is where I think Larry has established we have pushed the Threshold. Adolph's example that I retained in the quote demonstrates exactly what Larry has demonstrated with his testing. You can see he is clearly over the 160,000 RPM at 189,000 RPM and his 200 yard groups are more than 3 times larger than his 100 yard groups indicating non-linear dispersion. Now maybe if he used Matt's hard alloy with copper and water dropped, his 200 yard groups would shrink.

Thanks for posting those data. I hope to shoot like those guy some day.

Tim

[Eutectic]

Now, we need someone to start a thread on rifles using gain-twist. I always thought that would be the way to go with cast. Only one I can think of that used gain-twist, aside from a few muzzle-loaders was the Carcano. It's gotta be someone with more money than I have!

I think this is a good idea too. dtknowles has also mentioned it in regards to this thread.

I would like to see if gain twist could raise this RPM hurdle we are pursuing in this thread.

Harry Pope did some gain twist barrels many years ago and he may have forgotten more than we all know about rifling a barrel for cast boolits.

Heck, I think Pope's rifling configuration alone might raise the RPM hurdle.

Gain twist will 'mess' with engravings on our boolit? But it's down the bore with pressures and torque lower and still may pass the test; even raise the bar.

Eutectic

[Larry Gibson]

A test with a gain twist would probably prove interesting but what should the final bullet rotation be?

Since we already know we shoot higher velocity in slower twist barrels with cast bullets why bother with the gain twist? Why not just use the slower twist?

Larry Gibson

[MBTcustom]

A test with a gain twist would probably prove interesting but what should the final bullet rotation be?

Since we already know we shoot higher velocity in slower twist barrels with cast bullets why bother with the gain twist? Why not just use the slower twist?

Larry Gibson

In theory, because the reason for using a slow twist is so that the boolit is damaged less during launch. Ie. you can push up the RPMTH by delivering a less damaged boolit to the crown.
The big expensive question is: Which damages the boolit less? a 16 twist, or a 15-10 twist?
My money's on the 16 twist, but we'll never know for sure until somebody pony's up some serious cash.
Seems I read somewhere that the gain twist was tried and the results were demoralizing, but I can't remember which book I read that in.....

[357maximum]

Your right, I am worked up over this because it's tearing down my favorite forum...........
To the rest of you, please, if you disagree with the OP, go start your own threads on what your research is telling you and leave this viewpoint out of it, and stay out of this discussion.

If you think for one minute that true heated/opinionated discussions BASED ON EXPERIENCE are what is bringing this forum to it's knees you could not be more wrong in my opinion. Look around in the staff discussions (I cannot provide a link as I no longer have access to that info) and find where I nominated Mr. Gibson for the Golden Boolit Award back when I was a mod......heated/opinionated discussions are what used to drive this forum to the truth and also towards the advancement of the common good. A mod taking sides and snuffing out the other viewpoint(s) is not gonna help........the problems this forum face have ZERO to do with heated discussions and opposing ways of interpreting the same info. Further thoughts by me are not wanted here......I can live with that.....so my final thought.........just because someone says this is the way, does not mean he is right...or wrong.....anything is possible with cast if you seek it....you may fall face down in the mud trying, but you will get farther swinging for the fence........ is all I got to say...good day/good week/good life/goodbye.

[MBTcustom]

If you think for one minute that true heated/opinionated discussions BASED ON EXPERIENCE are what is bringing this forum to it's knees you could not be more wrong in my opinion. Look around in the staff discussions (I cannot provide a link as I no longer have access to that info) and find where I nominated Mr. Gibson for the Golden Boolit Award back when I was a mod......heated/opinionated discussions are what used to drive this forum to the truth and also towards the advancement of the common good. A mod taking sides and snuffing out the other viewpoint(s) is not gonna help........the problems this forum face have ZERO to do with heated discussions and opposing ways of interpreting the same info. Further thoughts by me are not wanted here......I can live with that.....so my final thought.........just because someone says this is the way, does not mean he is right...or wrong.....anything is possible with cast if you seek it....you may fall face down in the mud trying, but you will get farther swinging for the fence........ is all I got to say...good day/good week/good life/goodbye.

You don't understand.
I'm not trying to snuff anyone's opinion out. Unlike the people who refused to teach me anything more about shooting HS cast lead unless I BAN LARRY GIBSON FOR NO REASON WHICH I REFUSED TO DO!!!!
talk about snuffing out information! That's about as low/underhanded as you can get, and why I am so very angry!

That's why I'm doing what I am doing! Even after all that, I want to hear all the sides, but this has gone beyond heated discussions online here.

Larry even offered in good faith to meet one member while he was in that members state and was turned down flat like he was scum.
That's not even getting into the death threats.
No, I'm not making any of this up. I have emails and phone conversations to back up what I am saying.

DO NOT accuse me of trying to silence anyone. I'm just trying to hear all sides and get people to quit acting like this, and if you think it is not having a negative effect on the forum, you are dead wrong. No one should have to endure that level of hatred for posting their opinion on what happens to a piece of lead in flight.

[swheeler]

LOL Newtire you and LoveLife must really like the Idea of that gain twist.
I don't have any experiance with the process personally I have heard from both sides of the camps for and against. I know that several barrel makers (quality) do offer this service and product at a reasonable rate. The Carcano I'm iffy on that one as most have been probably had more damage from bad cleaning methods than shot out. I think I would lean towrd a new barrel if I wanted to play this route for testing. It would be interesting to utilize it during this same Topic for testing because IF that gain was finished at the same twist say a 1-14 then it "could" show differant results as to where that "hurdle" is.

I thought Colt used gain twist barrels on their C&B revolvers, could be wrong though. Bartlein offers transitional rifling(gain twist) and suggest it could be useful for cast bullet shooting, but at a much lesser "gain" on the twist than as used in the Carcano.

[swheeler]

Darn it thank you I could not remember if Bartlien or Brux offered it.
I would have to look up the old Colt pistols but I suspect you are correct But right off memeory I can not validate that. I do know a Lot of Smiths made gain twist in Black powder and was reportably accurate.
I copied this from Bartleins site:
For a .22 rimfire shooter or a cast lead bullet shooter, we can increase the twist very slowly. As an example, from 1-16.25 at the breech and end with 1-16 at the muzzle, on any length of barrel being made. The rifling machine will automatically calculate out the twist rate over any given length of the barrel.

[swheeler]

I think the info for Carcano came from here, but could've been another site? Twist started at 11 and went to 8 at muzzle, I can see this not being good for cast bullets in them, lots of gas leakage by muzzle exit.

[Larry Gibson]

...........so my final thought.........just because someone says this is the way, does not mean he is right...or wrong.....anything is possible with cast if you seek it....you may fall face down in the mud trying, but you will get farther swinging for the fence........ is all I got to say...good day/good week/good life/goodbye.

I am not a "mod" but I have been on this forum a long time. This how I see it; first of all I don't think this discussion or any one like it is "bringing this forum to it's knees". If we didn't have discussions like these we would make no progress at all. We might just sit around in purple and sing "I love you, you love me". No one has to read this thread. They do because they want to. If they don't like it they can stop reading anytime. Everyone has their own mouse and bliss is just a click away if they don't like it.

Yes some have left. I have almost left a couple times myself in anger. But the more I thought about all the good members here who I helped and who helped me learn more about cast bullets I chose to stay. On of those who convinced me to stay was you 357maximum. You and I have disagreed several times, mostly based on semantics though. This is a forum. It is a place for discussion. Discussions by their very nature many times are opposing viewpoints. Granted we do need to conduct ourselves in a reasonable manner even though we may disagree. To those who don't like the discussions don't read them. To those who want to leave, leave. There are many members here with a lot of knowledge left to pick up the football and run with it. I've seen no lack of posting information or asking questions since several "old timers" have left. Enough said on that.

Now to the crux of my post; you are absolutely correct in that there are many ways to accomplish the same thing. No doubt about that. But those different ways are with in the laws of physics and ballistics. That is the problem with some; they think they have the power, knowledge or ways of doing something that will violate those laws. No matter how some may wish they did the fact is they don't. So, there are different alloys to use, different powders to use, different bullet designs to use, different lubes to use, etc. Yes there are a lot of variables we can use to do the same thing. But we are not going to violate or change the laws of physics and ballistics. The foolishness comes from those who think they can and argue vehemently that they can.

I understand that it is probable there is a "limit" to just how fast we can push a naked cast bullet of ternary alloy with accuracy (2 moa or less with linear group dispersion as the range increases). I do not know what that "limit" is with ternary alloyed naked cast bullets yet as I have not found it. I have found now through continued experiments measuring accuracy, velocity and pressure that there are other "games afoot" that seriously affect the solid state of the bullet. I have found the RPM threshold for these ternary alloyed naked cast bullets with barrels of 10" twist, of 12" twist and of 14" twist. I am next going to find it with the 16" twist. Each time I am able to control the RPM a higher velocity with accuracy is attained. The pressure and plasticization of the bullet during acceleration to such HV is now a problem to overcome if possible. Where the probable limit is I do not know.

I will ask once again to those who chose to post on this thread that my experiments are to determine how high a velocity we can push a ternary alloyed naked cast bullet to and yet maintain accuracy. That is with any twist. Let us keep to the topic of this thread. Please stop attempting to obfuscate the results of these test (for personal or any reason) by the use of other alloys or by posting what is "thought" someone else did. If you have conducted tests with targets, chronographed and load/test data with the use of ternary alloyed naked cast bullets that differ in results or are the same as these tests I have conducted then by all means post them. Let us discuss them. Those of us interested in this are interested "in the facts, just the facts". Let us continue to learn.

If you (btroj or anyone else) wants to push the RPM Threshold, jump it, hurdle it or whatever with whatever cartridge in whatever rifle then let's start a new thread and get on with it.

Larry Gibson

[swheeler]

Didn't mean to muddy the waters, the gain twist subject was brought up so thought I would add some info, sorry. No Hijack Intended.

[ol skool]

Larry:

noobie here, THANK YOU for your hard work, meticulous records and clean experimention. I (maybe the only one) am VERY interested in seeing your data for the 16" twist esp. relative to 14" twist you have tested. I couldn't determine whether you had it in hand or was waiting for it, nonetheless I have a request. If you have that gun ready to go, back away from the computer and go shooting.

Take Care,
Steve

PS: dtknowles post #132 - Good catch, real time data...

[Eutectic]

A test with a gain twist would probably prove interesting but what should the final bullet rotation be?

Since we already know we shoot higher velocity in slower twist barrels with cast bullets why bother with the gain twist? Why not just use the slower twist?

Larry Gibson

I believe it's the small number on the gain... In other words a 16-10 gain twist would achieve a 10" RPM rating....

I see the big advantage being at the start especially if the 'gain' allowed full engraving at a good reduced twist rate. Be 'maybe' better with heavy weights if case capacity will push them to high velocity?

It would be nice in this equation though; sometimes the solution isn't where it is expected....

Eutectic

[dtknowles]

In theory, because the reason for using a slow twist is so that the boolit is damaged less during launch. Ie. you can push up the RPMTH by delivering a less damaged boolit to the crown.
The big expensive question is: Which damages the boolit less? a 16 twist, or a 15-10 twist?
My money's on the 16 twist, but we'll never know for sure until somebody pony's up some serious cash.
Seems I read somewhere that the gain twist was tried and the results were demoralizing, but I can't remember which book I read that in.....

a more fair comparison would be a gain twist that starts a zero and ends at the muzzle at a 16 twist compared to a straight 16 twist. Which do you think would damage the bullet more? Both should stabilize bullets of the same weight. The reason to go with faster twists is to shoot heavier bullets. I am pretty sure a 16 twist will not stabilize a 220 gr. bullet in 30 cal. I think even 180's would be iffy.

Tim

[frnkeore]

Goodsteel says:

Larry even offered in good faith to meet one member while he was in that members state and was turned down flat like he was scum.

Blanket statements aren't good! I want to clear up my part of the above statememt, whether it's OT or not!

larry offered and I invited him to come to my range here in Oregon, to shoot in front of other witnesses. He said that he still travels back to WA and it's right on I-5. I have not resended my offer and larry has not taken me up on it since that time.

Frank

[frnkeore]

Regarding gain twist, the formost maker of gain twist in North America is Ron Smith of RKS barrels in Canada. I shoot with him at the yearly match that I attend in Spokane, WA. In general, his barrels double the twist rate.

He says that the gain offers no advantage in accuracy but, in high power, with jacketed bullets, the barrel life is approx. doubled. His barrels win most of the schuetzen matches in the West and he says that the reason that his barrels have a advantage in cast is the sight choke that he puts in them.

Frank

[Larry Gibson]

Goodsteel says:


Blanket statements aren't good! I want to clear up my part of the above statememt, whether it's OT or not!

larry offered and I invited him to come to my range here in Oregon, to shoot in front of other witnesses. He said that he still travels back to WA and it's right on I-5. I have not resended my offer and larry has not taken me up on it since that time.

Frank

I haven't been up there since that offer was made. I don't travel on I-5 from here to WA or back so you are out of the way. I made the same offer to you to come down here.......is that supposed to mean something that neither of us made it? No, it simply means we will shoot together when I can make an effort to get to your location sometime.

Besides, goodsteel was not referring to you.

Larry Gibson

[frnkeore]

I haven't been up there since that offer was made. I don't travel on I-5 from here to WA or back so you are out of the way. I made the same offer to you to come down here.......is that supposed to mean something that neither of us made it? No, it simply means we will shoot together when I can make an effort to get to your location sometime.

Besides, goodsteel was not referring to you.

Larry Gibson

Since the person wasn't named or that it isn't someone in this discussion, I just wanted to make it clear that it wasn't me.

Frank

[Larry Gibson]

frnkeore

No, it wasn't you. But to our previous discussion here's what you actually said; "A quick little reply lary and then I am acually done with it!" (where's the spelling Nazi's when you need them[smilie=l:) I took it to mean you didn't want to chat with me anymore.....apparently you do?

Well if so then to the point; You just don't get it do you? This thread is about pushing a ternary alloyed cast bullet to as high a velocity as possible while maintain a certain level of accuracy (2 moa or less). All of your quoting of CBS match results tells us nothing we don't already know; yes you can push the RPM threshold to 160,000 RPM quite successfully. We've been doing that for some time. The point of the CBA matches is accuracy only; they don't care what the velocity is. Velocity with accuracy (not match winning accuracy but accuracy) is our purpose/goal here. What part of that don't you understand?

The idea is to push to as high a velocity as possible regardless of the twist. If you'll bother to go back a few posts and look close at the 2620 fps groups you'll see what the goal is. While we appreciate your love for CBA match results that level of accuracy at that low of velocity is not the goal here. Get it?

Now you apparently have an interest, an ability and some equipment. So why not do something constructive for a change? I believe you have a M98 in 8x57 and a very good Loverin mould? Why don't you give us ten 10 shot groups shot at 100 yards covering 1600 fps to 2400 fps with; a faster burning powder such as 4227, 2400 or even H110 and a medium burning powder such as 3031, 4895, 4064 and with a slower burning powder such as 4350, RL19, H4831? Post the data (group size and velocity) and we'll graph them out to see where accuracy goes south (exceeds the RPM Threshold) with each. Then we'll pick a load below the found RPM Threshold with each powder and a load above the RPM threshold. You can then shoot 10 shots with each at 100, 200 and 300 yards to find out if the group dispersion is linear or non linear. That should definitely show us something, ya think?

So there's your big chance frnkeore, to show us I'm wrong and to show us you can really do something other than quote someone else's work.

Larry Gibson

[MBTcustom]

Well Larry, regardless of whether Frank takes you up on your challenge, I'm going to. I have a nice Mauser with a nice 10 twist barrel, and enough five shot loads to incrementally work right over the proposed RPMTH, and if it's not raining Sunday (I'm praying) I'll be doing a little testing with medium burn rate powder. I may haul my press to the range with me along with some fast and slow burn powders.
If that happens, I'll post some pictures here with your permission.

And no Frank, I wasn't talking about you in my previous post.
What do you say? Wanna burn some powder with me?

[btroj]

A gain twist is intriguing but I wonder how it will do with cast. Will the changing angle of the lands cause leading? Will a good seal be easily maintained along an ever changing landscape?

I don't know.

[dtknowles]

A gain twist is intriguing but I wonder how it will do with cast. Will the changing angle of the lands cause leading? Will a good seal be easily maintained along an ever changing landscape?

I don't know.

I have asked myself the same questions and have not convinced myself that I could guess how it would work for better or worse. I think that since the radius of curvature is decreasing (getting tighter) so that should work to cut-off blow-by but it means the lead is being continuously worked the whole trip down the barrel. Only testing would tell.

Tim

[swheeler]

Brad maybe you can settle this once and for all when your new toy arrives. Seems like Gears rifle had the same twist as yours, 1 in 12 IIRC and remember reading a post by him where he hit a "wall" right at 2400 fps. Hum that's about 144000 rpms, wonder what happened? I will stay tuned for your test results before I make any decisions of my own;)

[Dutch4122]

Last night after Mike called me and asked me to get on this thread and post the results achieved thus far with my 03A3 Springfield I took a few hours to mull it over. Problems I had with even posting the information came from the fact that I knew there would be backlash. Not a huge deal.

However, it was not my intention to muddle up Larry's thread with my initial results obtained with a different type of alloy than he is working with in his testing. Notice that I mentioned in my post that this load needs more testing to see if it will stand up on paper. I also did add in to my post that I was using a different alloy than Larry.

My only intention was to help a fellow member who asked about the load that Mike mentioned. In hindsight, it would have been a better idea to PM dtknowles and give him the information that way or start another thread. Instead, the good old Cast Boolits thread drift that we are famous for has reared it's ugly head again. Not to mention the inevitable arguing over the distraction that drags the whole thing into the mud.

Larry and Tim do make a valid point. My post was off topic and could be counterproductive to Larry's testing.

Good luck with your discussion.

[swheeler]

Thread drift, NAW! I wouldn't do it on purpose and don't think you would either, it just happens.

[Larry Gibson]

A gain twist is intriguing but I wonder how it will do with cast. Will the changing angle of the lands cause leading? Will a good seal be easily maintained along an ever changing landscape?

I don't know.

Those are excellent questions. In addition would the changing angle add to the damage/imbalance done to the bullet?

Larry Gibson

[onceabull]

Dutch4122: Thread drift or not,I found enough value in your post to say THANKS..But,this being Cast Boolits,there has to be a ?... At the stated BHN of 28, is there anything available by actual testing,than shows some advantage to a copper enhanced alloy Vs.straight Linotype ??? Onceabull

[frnkeore]

frnkeore

No, it wasn't you. But to our previous discussion here's what you actually said; "A quick little reply lary and then I am acually done with it!" (where's the spelling Nazi's when you need them[smilie=l:) I took it to mean you didn't want to chat with me anymore.....apparently you do?

Well if so then to the point; You just don't get it do you? This thread is about pushing a ternary alloyed cast bullet to as high a velocity as possible while maintain a certain level of accuracy (2 moa or less). All of your quoting of CBS match results tells us nothing we don't already know; yes you can push the RPM threshold to 160,000 RPM quite successfully. We've been doing that for some time. The point of the CBA matches is accuracy only; they don't care what the velocity is. Velocity with accuracy (not match winning accuracy but accuracy) is our purpose/goal here. What part of that don't you understand?

The idea is to push to as high a velocity as possible regardless of the twist. If you'll bother to go back a few posts and look close at the 2620 fps groups you'll see what the goal is. While we appreciate your love for CBA match results that level of accuracy at that low of velocity is not the goal here. Get it?

Now you apparently have an interest, an ability and some equipment. So why not do something constructive for a change? I believe you have a M98 in 8x57 and a very good Loverin mould? Why don't you give us ten 10 shot groups shot at 100 yards covering 1600 fps to 2400 fps with; a faster burning powder such as 4227, 2400 or even H110 and a medium burning powder such as 3031, 4895, 4064 and with a slower burning powder such as 4350, RL19, H4831? Post the data (group size and velocity) and we'll graph them out to see where accuracy goes south (exceeds the RPM Threshold) with each. Then we'll pick a load below the found RPM Threshold with each powder and a load above the RPM threshold. You can then shoot 10 shots with each at 100, 200 and 300 yards to find out if the group dispersion is linear or non linear. That should definitely show us something, ya think?

So there's your big chance frnkeore, to show us I'm wrong and to show us you can really do something other than quote someone else's work.

Larry Gibson

larry says:


Well if so then to the point; You just don't get it do you? This thread is about pushing a ternary alloyed cast bullet to as high a velocity as possible while maintain a certain level of accuracy (2 moa or less). All of your quoting of CBS match results tells us nothing we don't already know; yes you can push the RPM threshold to 160,000 RPM quite successfully. We've been doing that for some time. The point of the CBA matches is accuracy only; they don't care what the velocity is. Velocity with accuracy (not match winning accuracy but accuracy) is our purpose/goal here. What part of that don't you understand?

This is actually the title of this thread:

"RPM Threshold; A Tale of Three Twists, Chapter II"

Nothing about velocity. I think you need to open another thread about velocity if that is what you want to talk about. They are two different things.

With what we have learned in this thread, do you at least concede that YOUR "threshold" is actually somewhere between 160,000 and 190,000 RPM and not 120,000 to 140,000 RPM or, can larry, never say that he was mistaken?


"A quick little reply lary and then I am acually done with it!" I took it to mean you didn't want to chat with me anymore.....apparently you do?

I did say that, it was in reference to THAT thread and that thread only. The reason that I said it that way is because, you've said that you where "done with it" in that thread and many threads that we have had discussions in but, you have NEVER kept your word when you have said it. I didn't repost in that thread. I guess you call it "being a man of your word".

Dinner time, more to follow.

Frank

[Larry Gibson]

btroj

yes Larry, that Dutch did DOES prove something. I mentioned the need for hundreds of groups as you mentioned. Did you fire those hundreds of groups with each rifle? Did you vary anything? what makes your testing any more valid than what Dutch did?

Have you not really read chapters 1 & 2? Have you not read any of the reports I've made in other threads on this topic on all the groups I've fired, different bullets used (311299, 311334, 311284, 311291 (2 different moulds), 311041 (2 different moulds), MP 30-180-FN, 311466 (2 different moulds), 311465 (2 different moulds), 30-150-FN, C312-155-2R, LBT 30-160, 311359, 311413), different powders used (4895, Varget, 4064, RL19, AA4350, IMR4350, H4831, RL22, AA3100), different primers used (WLRs, CCI 200s, Rem 9 1/2s and Fed 210s), different GCs used (Hornady, Lyman (new and old), Blammer's and my own aluminum and brass and different lubes (Javelina, Tamarack, Lars 50/50, 2500+, LBT Blue, LBT Blue soft, Carnauba Red, RCBS rifle, 3 different Lyman lubes and a couple others I don't recall off the top of my head. I have tested all the variables mentioned including different bullets sizings (.308, .309, .310, .311, .312 and even .314) and several different alloys (6 to be exact). No I did not fire all those with each rifle because as you indicate the task to do that is daunting to say the least. What I found was what worked in one rifle the best most often worked the best in all 3 rifles. Yes some favored one a little more than the other but there was no set pattern as to which rifle. Conversely I found if one item worked poorly in one rifle it also worked poorly in all three rifles. As I narrowed down the variables to what was working I also narrowed the test to one rifle and then used what worked in it. As my objective was to push a ternary alloyed naked cast bullet to as high a velocity as possible with accuracy I focused on the 14" twist Palma rifle because the 10 and 12" twist rifles could not push velocities and hold accuracy to the level it could.

Now as to yours and a couple others continuing comment about the "different barrels". Understand this; 3 different twists were required. Ergo no matter if the barrels were from the same maker of the same make of steel or had the same contour the important part to the test, the interior of the barrel i.e the bore, would be different. This is because the twist is different so the cutter, the button or the mandrel that the grooves were made with would be different. Your continuing complaint that they are "different" is a moot point because they have to be different if we are going to have 3 different twists (note the adjective "different"). The scientific methodology for testing such is to use comparative analysis. In this case we simply compare a loss or increase in accuracy of a particular barrel to itself since the point of interests is simply that point (velocity and RPM) at which accuracy begins to degrade for each barrel. That 12" twist M70 Target rifle is more accurate than the 14" twist Palma rifle yet the Palma rifle shoots more accurately at a higher velocity with cast bullets. Yes they are "different". Different barrels or not; show me your 10" twist or even your 12" twist barreled rifle that is shooting with the same accuracy at 2620 fps as the 14" twist barreled rifle is with naked cast bullets of a ternary alloy. You can't, I can't and no one else has. The reason is because there is a difference; guess what that difference is?

Everyone except you and a couple others understand that. You will begin to understand it as you begin to push velocities up in the rifle goodsteel is building for you. You spent a whole long post outlining almost the exact testing methodology you need to use that I have been using for the last, what(?) 6 or 7 years in my own testing? And then you say you don't like my methodology.....that's the pot calling the kettle black isn't it?

Larry Gibson

[Larry Gibson]

larry says:


This is actually the title of this thread:

"RPM Threshold; A Tale of Three Twists, Chapter II"

Nothing about velocity. I think you need to open another thread about velocity if that is what you want to talk about. They are two different things..........Frank

I suggest you go to post #1 of this thread ("RPM Threshold; A Tale of Three Twists, Chapter II" which the "II" means it's a new chapter with a new direction) and read the 2nd paragraph which states; "My testing and load development then took the turn to see just how fast I could push a regular cast bullet of a ternary alloy with the 14” twist Palma rifle and maintain accuracy of 2 moa or less and maintaining linear group dispersion out to aminimum of 300 yards. "

Apparently with this being a gun related shooting forum you don't understand what "how fast I could push " means..........so apparently what you think isn't correct?

Since you don't understand that the rest of your post isn't worth responding to, especially since you fail to respond to whether you are going to do the test I suggested and that goodsteel is willing to participate in. If not it is obvious your intent is simply to criticize me and interrupt this thread with your nonsense. Do us all a favor and contribute something useful for once.

Larry Gibson

[Dutch4122]

Dutch4122: Thread drift or not,I found enough value in your post to say THANKS..But,this being Cast Boolits,there has to be a ?... At the stated BHN of 28, is there anything available by actual testing,than shows some advantage to a copper enhanced alloy Vs.straight Linotype ??? Onceabull

Question answered by PM.

[frnkeore]

Well, larry, I do think your intent for this thread was to see how RPM affected your ACCURACY with 3 different rifles, with 3 different twist and not just how fast your 14 twist would go. Am I wrong? What does the "tale of 3 twist" mean? The way I read this thread is that you were proving that RPM was the reason that accuracy fell off as velocity increased. Am I wrong again?

I would like to ask you again:

With what we have learned in this thread, do you at least concede that YOUR "threshold" is actually somewhere between 160,000 and 190,000 RPM and not 120,000 to 140,000 RPM or, can larry, never say that he was mistaken?

Frank

[Nrut]

357maximum is way to kind.[smilie=s:

My rifle is a CMP Greek return Remington made 03A3 produced in May, 1943; with a brand new (in the wrapper & cosmo'd when I bought it) Remington made July of 1943 two groove replacement barrel. Barrel was installed by Badgeredd. As of this date the barrel has had only 103 rounds fired through it of the following load and no other:

Bullet Design: RCBS 30-180-SP (Late version, bore riding nose)
Actual weight lubed & checked: 190 grains

Cast of an alloy that is: (according to Badgeredd's alloy calculator)

92.35% Pure lead and other trace elements
3.73% Tin
3.5% Antimony
.22% Copper
.20% Arsenic

(Note: This is a copper enhanced alloy, and not the type of alloy that the OP used in the testing he has presented in this thread)

The easy way to mix this alloy is to follow this simple recipe of 8 lbs. Clip On Wheel Weights, 1.5 lbs. of Pure Lead, and .375 lbs. of Rotometals Grade 11 Babbit for a 10 pound pot. Double the amounts for a 20 pound pot and quadruple the amounts for a 40 pound pot, etc. Here's a hint, don't assume that your soft range scrap is in fact pure lead that's ok to use in this mix, it probably isn't. Use what this recipe calls for, don't deviate. There are enough variables to deal with in Clip On Wheel Weight alloy as it is. No need to have the other components skewed.

Bullets were water dropped from the mold into a five gallon water bucket. They were allowed to stabilize for two weeks, BHN was 28, sized/checked to .310" diameter and lubed with MML + 5% Soap. My mold casts a bullet nose that is .302" diameter using the above alloy from my mold.

The load itself is as follows: (loaded and shot as projected in Quickload)

46 grains of IMR-3031

CCI #200 Large Rifle Primer

54,000 psi / 100% powder burn / muzzle pressure = 7,849 psi

5 shot average over the chronograph is 2,510 fps. I was hoping to match the U.S. MkI ball load which was a 175 grn FMJ Spitzer at 2,600 fps. However, given the accuracy potential this load is showing I'm not going to quibble over 90 fps, especially since my boolit is 15 grains heavier.

Ok, so here's the deal with this rifle and load. When I say 103 rounds I mean that is the absolute total number of rounds which have ever gone down this barrel, period. The barrel has only ever fired this particular load. The 1st round went down the tube at the end of May. First 5 shots fired went into 3" at 100 yards with one flier I believe to be the very first shot opening the group from 2.5" to 3" Either way, that is within acceptable U.S. Ordinance accuracy standards for these rifles as they came off the line at any manufacturer. I was shooting that day with Castboolits Member "Mostlyonthepaper" and he can verify this plus I have the target saved. Minor sight adjustments were made and after that the rifle has not been put through any serious target work since; just pounding rocks and steel at 250 yards. The plan has been to give it about these 100 rounds of shooting for the bore to season with lube before getting serious on paper. While shooting at Badgeredd's place on June 8th the rifle seemed to be shooting better as the round count rose. 357maximum was spotting for me through 10x binoculars and advised I was hitting the same 2"-3" spot on a rock @250 yards repeatedly before I split the thing.

So, the load shows some real promise out of a 24" barreled 03A3 with issue receiver sights. Enough to warrant some real testing.

dtknowles -

Right off the bat I will tell you this. Bullet fit is king. Also, my rifle has a 24" barrel and yours has a 22" barrel. I believe, based on my experience, that keeping muzzle pressures below 8,000 psi is very important for even usable accuracy. Your barrel will produce higher muzzle pressures than mine with the same load due to the fact that it is shorter. Find a bullet in the 200-210 grain weight range when cast out of this alloy that fits your rifle properly when chambered. Start out at 43 grains of 3031 and work up. If you have the alloy, lube, and fit right I think you could find a good load.
Thanks for your write up Matt..
Always interesting to see how you, Mike, Bruce & Edd are approaching the HV with cast puzzle..
I use a lot of information that you all post and I bet others do also..
Wasn't really planning on fooling with HV this summer myself but happen to have a Smith Corona O3A3 (43) similar to yours
It was the first rifle I shot cast out of and did quite well at low velocity back when my eyes where good..
My target was a small black square the same width as the front sight at 100 yards..
Also have a new in the white two groove wrapped in paper with grease..
Naw, think I'll just shot PP when I get to it..
But I will try 3031 thanks to your post..


Cheers

[frnkeore]

For those interested in gain twist barrels and what they can or can't do, contact Ron Smith of RKS barrels in Canada (costs no more to call than the US). He has been making, shooting and selling them for more than 20 years.

The way he got started was buy shooting his barrels in matches and winning. His business has snowballed in the last 10 years.

His number is:

403 631 2405

Tell him, Frank Elliott, in Oregon sent you.

Bartlein is another barrel maker that does gan twist. I believe they started making them about 2 years ago. I don't have the number but, a search will bring it up.

Frank

[Mik]

As a new member on this forum, I can't really see how this became an argument of great proportions.

It seems like a simple scientific fact that an imbalanced, asymmetrical, rotating object will become more and more unstable as it rotates faster and faster. An imbalanced wheel on a car will feel fine at 30mph but not at 70mph.

It also seems like a scientific fact that a PERFECTLY balanced and symmetrical object will NOT be affected by increasing rpms because the forces acting on the object remain exactly equal in opposite directions. I think btroj mentioned that the answer lies in creating more balanced projectiles, I think he is correct.

That being said, contractors for NASA have difficulty manufacturing perfectly balanced objects in their multi million dollar facilities. It would be unreasonable to think a guy melting wheel weights in his garage and pouring them into a $100 mold could manufacture a projectile that will be perfectly balanced and symmetrical after being squeezed through a rifle barrel. (does anyone disagree?)

So, logic says there must be an rpm threshold somewhere, there is no such thing as a perfect projectile. Some might get closer than others, but I can guarantee none are perfect when they emerge from the bore.

Larry presented evidence that suggests that with his manufacturing skill (likely greater than that of many members) and his manufacturing equipment (likely similar to that of many members) his projectiles appear to run into that threshold somewhere within the ballistic capabilities of the .308.

Why the huge fight?

[MBTcustom]

Well, larry, I do think your intent for this thread was to see how RPM affected your ACCURACY with 3 different rifles, with 3 different twist and not just how fast your 14 twist would go. Am I wrong? What does the "tale of 3 twist" mean? The way I read this thread is that you were proving that RPM was the reason that accuracy fell off as velocity increased. Am I wrong again?

I would like to ask you again:

With what we have learned in this thread, do you at least concede that YOUR "threshold" is actually somewhere between 160,000 and 190,000 RPM and not 120,000 to 140,000 RPM or, can larry, never say that he was mistaken?

Frank


Hey Frank, I've read Larry's threads on this subject and and from that brief perusal I would say "it depends".
Why do you keep trying to force him into saying that it's a limit?
If he explains it from the viewpoint of RPM you bust him with FPS. If he explains it from a viewpoint of FPS you bust on him with RPM. It's circular reasoning, and I really don't think you are after any answers here. I think you just want to watch Larry dance, insure thread drift, and basically fill up the thread with anything but useful information.
This is trolling.
Why don't you explain what you have done in your rifle hmmmmm? What have you demonstrated that negates this? (or are you actually doing your shooting the same place you pull your information from....online?)
Seems like anytime anybody asks you to give information about what you have done, it's always somebody else, long ago and far away, but written online. Heck you weren't there, it could have been a typo for all you know but it says something different so that'll work. Is your whole argument based on what you read online? That's really weak man.

All Larry is saying is that with a standard trifecta alloy (that's lead, with a sniff of tin and antimony, any mix you like) each rifle and load will have it's own RPMTH. The only way to be sure what that will be is to shoot it, and work up till accuracy falls off. However, the biggest indicator of approximately where that point is, seems to be able to be determined by twist rate. This thread was about demonstrating that to the masses.

You say it's wrong based on alloy change. OK so what? Most of us are not going to go through the hurtles of mixing copper rich alloy. We want to know what is possible with a trifecta alloy (that's lead, with a sniff of tin and antimony, any mix you like). We all know we can push the RPMTH up to about 300,000RPM just by using standard jacketed bullets. To use that argument to say the RPMTH is bunk is just silly.
I'm willing to listen, and I think Larry is too, if some real, first hand, evidence is brought forth that uses a standard trifecta alloy (that's lead, with a sniff of tin and antimony, any mix you like).

Would you please speak plainly? What have you seen that makes all of this null and void?

Personally, I'm starting to really buy the RPMTH as a window of truth if not the whole picture. I am taking this position based on what my rifles have done.
For instance. I have a type 38 Arisaka. It is barreled with a .307 groove 1-11.25 twist barrel 22" long. It is bluprinted, has a 3lb trigger, bedded with milspec bedding compound, the rings are lapped, and installed correctly. It's chambered in 308 Palma.
With jacketed, it's a one hole rifle. Shoots 168 Hornadys into a 1/2" cloverleaf at 100 yards.
Now, the first time out with that rifle (not having read Larrys RPMTH threads) I had it loaded up to about 2400fps with IMR3031, a duplex load of WC867 (that was actually 2100fps out of this rifle) and 4895. That rifle shot patterns at 50 yards with everything but the duplex load. Very disappointing. I've shot better groups with my shotgun launching round balls out of a smooth 12 bore. A few weeks ago I loaded up some 1800FPS loads with 3031 and shot about 1" at 100 yards.
Now granted, that was just one outing, and I'm not nearly finished with that, but when I read what Larry has written here, it sure gives me pause for thought, and one group from my rifle trumps 1000 pages written online.

[PAT303]

I've got to say I'm with Tim,why don't people simply post up their results in plain English so the rest of us can learn,why try to discredit one another?,why are we all here?,to learn. Pat

[garym1a2]

The huge fight is because many people don;t want to agree with Larry. Even though they know that barrel twist has a huge affect with bullet preformance either jacketed or cast. My cast experance with Rifles is limeted to a Blackout 1:8 at 1700fps and a Rossi .357 at about the same speed. My results where accecptable to me but I am not trying to push the limit with these as their goals are piggie blaster for the Rossi and Short range 3Gun for the Blackout.

With Jacket Rifles I have more experance and see where most of the guns made the twist is wrong for the shooters of them. Back in the early 90's when I was shooting high power I purchased a new Colt Hbar with a 1:7 twist, using UMc I could not get decent groups at 100 yards and was off paper at 300 yards. Yet the same rifle with 69 gr match kings was good enough to shoot a 99 prone at 300 yards once and clean at 200.

Now days most AR's come with 1:7 twist, even the military. Yet the preformance is poor with the 55gr and 62 gr bullets they use. Yet a 1:9 barrel works great with these bullets.





As a new member on this forum, I can't really see how this became an argument of great proportions.

It seems like a simple scientific fact that an imbalanced, asymmetrical, rotating object will become more and more unstable as it rotates faster and faster. An imbalanced wheel on a car will feel fine at 30mph but not at 70mph.

It also seems like a scientific fact that a PERFECTLY balanced and symmetrical object will NOT be affected by increasing rpms because the forces acting on the object remain exactly equal in opposite directions. I think btroj mentioned that the answer lies in creating more balanced projectiles, I think he is correct.

That being said, contractors for NASA have difficulty manufacturing perfectly balanced objects in their multi million dollar facilities. It would be unreasonable to think a guy melting wheel weights in his garage and pouring them into a $100 mold could manufacture a projectile that will be perfectly balanced and symmetrical after being squeezed through a rifle barrel. (does anyone disagree?)

So, logic says there must be an rpm threshold somewhere, there is no such thing as a perfect projectile. Some might get closer than others, but I can guarantee none are perfect when they emerge from the bore.

Larry presented evidence that suggests that with his manufacturing skill (likely greater than that of many members) and his manufacturing equipment (likely similar to that of many members) his projectiles appear to run into that threshold somewhere within the ballistic capabilities of the .308.

Why the huge fight?

[Hamish]

The Bell Curve.

There was a post on page three stating that all results must be comparable using all powders, irregardless of burn rate. Think about that one for a moment. I do not wish to start a fight, or even a discussion, but for me, this seems a patently false assumption.

Painting oneself into a corner and refusing to come out even when shown that the paint is dry is a sad thing to see.

The universe operates under the Bell Curve and shooting, particularly shooting cast, is no exception. IF we had enough resources to test every combination of alloys, lubes, powders, etc., then we could graph the "window" that each combination would work, and work best in.

I see all the variables as overlapping Bell Curves, when the all overlap, it works. When they all overlap in the most favorable range, it works best. When they dont overlap, you get poor results or failure.

I have a hard time understanding the efforts made to nail the work done on this to one variable or another, when it is all the ingredients in the recipe that make the cookie.

Frkeore, I can find nothing in your posts to objectively refute anything that Larry has presented. I do however, perceive a personal animosity and not much more.

[waksupi]

I've been meaning to do some experimenting in the testing area. I want to see if an original poster can open and close a thread at will, to be able to put relevant information into a thread without others interfering with the transfer of information. Naysayers could open their own threads. There have been a lot of electrons senselessly and worthlessly wasted in this thread. Heaven forbid someone should do research and post it.

[Larry Gibson]

Well, larry, I do think your intent for this thread was to see how RPM affected your ACCURACY with 3 different rifles, with 3 different twist and not just how fast your 14 twist would go. Am I wrong? What does the "tale of 3 twist" mean? The way I read this thread is that you were proving that RPM was the reason that accuracy fell off as velocity increased. Am I wrong again?

Yes you are wrong, read the 1st post in this thread; the answer is there.

I would like to ask you again:

With what we have learned in this thread, do you at least concede that YOUR "threshold" is actually somewhere between 160,000 and 190,000 RPM and not 120,000 to 140,000 RPM or, can larry, never say that he was mistaken? Frank

No I will not concede because what you want is based solely on your own opinion. The 120 - 140,000 RPM range for naked cast bullets of ternary alloy was derived from facts. Here is a graph of numerous loads I researched for another who couldn't understand. Notice the range of RPM with the numerous loads from several cartridges and rifles where the accuracy begins to deteriorate. I base it on proven demonstrated facts, not erroneous opinions.

Larry Gibson

108976

[popper]

garym1a2 (http://castboolits.gunloads.com/member.php?15096-garym1a2) I think you have it right, the Mil purposely reduces the effectiveness of their weapons & the makers copy it. Rotary inertia is 1/12*m*(3*bore^2+length^2) and is a force that tears our poor boolits apart. Out of balance mass just adds an m*delta D^2 component. Rotary inertia is related to rotary velocity (via torque) and related to fps by twist. It is also the component in gyro equations to provide stability. Jackets & PP are just a strong shell to contain the weaker lead. Cu, Ag, S and other additives add strength to Pb by placing 'bumps' in the Pb lattice so it doesn't 'slide' so easily. Sb/Pb as an aggregate of strong/weak metals, similar to concrete.
So to answer several questions: 1)yes there is a RPMTH. 2) It is related to fps by twist. 3) If you want to extend the RPMTH, change the twist or alloy or use jacketed or PP. There is an old southern saying I learned. Some are so ornery they will argue with a stump (or chair).

[MBTcustom]

Larry modified his rifle to a slower twist, and has demonstrated that it works. He has achieved high speed accuracy.
Others chose to modify their alloy to a harder/tougher result and have demonstrated that it works. They also have achieved high speed accuracy.
Some others have chose to modify the surface of their boolits with a jacket of copper, paper, or plastic. They have achieved high speed with accuracy.
Some others have chosen to modify nothing, and they report nothing, they post nothing but hatred for this particular way of achieving these two goals.
I see that it buggs the fire out of some that this method works, and has more explanation and pictures backing it up than all the other methods combined (with the exception of the jacketed guys.)
That's what I don't understand (I am not kidding, I really don't understand it). If the other methods are so incredibly awesome, then why not post a group instead of an emotionally charged challenge to the OP's character? I mean Larry could be a complete feral human being, but that wouldn't change the fact that he did the work and explained his position. If this method works for people (and it does. I'm building their rifles) and they pursue it, why is that thought of as humping someones leg?

[357maximum]

Tim


MULL TH FOLLOWING STATEMENT OVER FOR A BIT:

I own slow twist barrels too.....why you spose that is????


.........and would I admit to it if I was trying to make Larry look like a fool???? Sometimes "easy" is good.....sometimes the "impossible" is fun to reach for also.......sure at times you are gonna swing so hard trying to get to the fence that you spin around and fall flat on your face while others point and laugh.......but......but....occassionally the ball goes over the fence and that is soooo damn sweet that you buy another "regular" rifle just so you can try it again.

I am not a wordsmith...I cannot express myself via the typed word as others here can......I am not a writer....I am not a ballistician.....I am a try it til I get it kinda feller....I spent most of my working life diggin holes/ditches and filling them with a piece of pipe for more reasons than the simple fact that I truly liked the work. I truly am playing Tetris on high speed with one hand tied behind my back.....it is not by choice however.

[dtknowles]

Tim

You had it right before you switched variables to objectives. MY GAWD MAN this place can be like playing Tetris on the super duper advanced setting. :confused:

I am a different Tim but I like playing Tetris and have moved up a few levels, keeps you sharp.

I feel no shame in contributing to thread drift now as we are no longer having a technical discussion.

I just bought some copper bearing babbit. I will cast and shoot and post the groups. I can think of all sorts of thresholds I can break. Nobody ever told me what the threshold is for plain base bullets so I will have to find that myself. I will have to find someplace with a 200 yard range in southeast La.

Tim

[frnkeore]

Ok guys,
I feel like the messager that when he brought the truth to the king, was at once marched to the nearest wall and SHOT!

One guy says this:

"Frkeore (his misspelling not mine), I can find nothing in your posts to objectively refute anything that Larry has presented. I do however, perceive a personal animosity and not much more."

After I posted the match results with the rifle and all the loading data with it. For not just one person but three.

Match result data is one of the most reliable sources we have for what is actually true. Every match has approx a minimum of 10 witnesses to a max of 100 or more. If you believe a typo was entered 3 times or more well......... I don't know what to say. Match shooters are very zealous and a try to eleminate as many errors as possible, even with there equipment info.

I take offence to any referance of me being a "keyboard shooter" I have participated in rifle shooting matches (Bullseye pistol for 2 yrs, also) since 1982 and you can find my scores published in ISSA & ASSRA match results!

I am a student of rifle accuracy. I'm not a Master as there is ALWAYS something new to learn.

One thing that I don't understand on this forum, in general, is the lack of interest in what is the only organization that is in business to further the shooting accuracy of GC cast bullets, the CBA (Cast Bullet Assoc.). If you follow the results, posted in the match results, you WILL learn something. What happens at at the matches are FACT!!!! Not opinion.

I think that 357Maxium somed it up, very nicely as follows:

2. Honestly my biggest issue with Larry and his "research" is that (in my opinion) it is basically the same as researching the reason why a 4cylinder Ford tempo will not win the Daytona 500. Larry has set out to prove why mediocre boolits/alloys in mediocre guns are mediocre in performance fps wise...why I do not know...to each their own, but the way he gets fired up when someone tells him a V8 would work better in the Daytona500 leads others to get frustrated.....myself included.

To get the maximum proformance from a jacket or cast bullet rifle, you have to have a well bedded action, good barrel and as I posted earlier, the correct chamber and throating. Only with that will you get the most reliable and best available results.

Whether or not, I choose to shoot high RPM loads is irrelevant, my purpose here is TRUTH and accuracy in reporting Fact!

larry's report here is just that a report of 3 differnt rifles with 3 different barrels and how they shot with his skill level. It's not a scientific test. If his "Palma" rifle was built as a match rifle, it will alway produce more accurate results that the other two. The Palma rifle still isn't capable of the best cast bullet accuracy because the "palma" chamber (if it was cut with a Palma reamer) still doesn't have the optimum throating for cast bullet. It is optimum for the 155 gr Palma match bullet, nothing else.

I would be interested in anyones opinion that does scientific testing, as to how reliable this test would be to prove anything regarding a corralation of barrel twist vs velocity or if they think that "threshold" would be a appropriate term. It does make for a very conviniant term, though.

Put the blind fold on me and fire away ;)

Frank

[Larry Gibson]

You really want to degenerate this thread to such a low level personal attack? I don't.

None of the very few of you "others" who can only come up with personal attacks, in the end, as such have posted anything such as you profess; "I and others simply mention the fact that more is possible and it has been done with the right techniques/materials". If that is true then where are the results? Where are "right techniques/materials"? None of you have posted them. I have continually offered to assist you and the "others". What I've gotten is "Oh I don't have any particular bullet in mind and haven't made a decision on powder so it will take me years and hundreds of trips to the range to figure it out."

So if you and the "others" have it figured out why don't you show us right here right now? Why don't you then tell us how you did it right here right now? Then why don't you teach us how we can do what you and the "others" claim can be done right here right now? Numerous "leg humpers" through out this thread have asked any of you or the "others" to post anything to document what you claim you've done. None of you, not you nor the "others", have posted anything. You and the "others" have cried "wolf" so many times no one believes you anymore.

Since I began this discussing the RPM Threshold on this forum and perhaps on the old one I have proved the RPM Threshold exists. Legions of forum members who have found the RPM Threshold now understand what it is and what causes it. Knowing what the RPM Threshold is I have told them many, many times how to push the RPM threshold up. I have pushed the RPM threshold up and have posted the results on this forum with details in how it was done. I have helped numerous of them to do the same, I have offered continuously how they can do it also.

All you and the "others" have offered anyone is ".......more is possible.....if you want it......". Yet you offer nothing. I will give you credit with your admission of "......that's all I am ever trying to point out in this type of thread......" because that "point" is all you and the "others" make. You show nothing, you teach nothing. And now you have the unmitigated gall to call the rest of the forum members "leg humpers".

If you don't like the "drama" don't go to the play.
Doesn't matter what I think What matters is what all the forum members now think............

Might be wise if a moderator locks up this thread before it really get out of hand?

Larry Gibson

[Larry Gibson]

frnkeore

Why should we shoot you, you continually shoot yourself........mostly in the foot..........

Larry Gibson

[MBTcustom]

I expected you would ask for a blindfold.
Typical.
:kidding: