30-30 accuracy loads

[mainiac]

Im working with a 336a marlin in 30-30. 1949 model,with a very pretty nice bore. Using the lee 170 boolit.
My latest alloy is about 13.With this alloy,the gun shoots very,very small groups between 1600-1700 f.p.s. Sometime after 1850 or so,the gun starts shooting huge groups.Once 2000 arrives the gun is shooting around 4 inch groups.

I get no leading with this alloy,but i cant push it up to factory speeds.Using h-335 powder.
My other marlins can shoot cast right up to,and past factory speed with no issues.35 rem,32 special,,,have no issues.Is this because of the 30-30,s relatively fast twist?

Also, this boolit measures close to .309 on the nose,and engraves the rifling pretty severe.Am thinking about buying a 308041,,and am wondering if the nose cast a little thinner then this lee?Maybe this old gun,has a tight throat?

[Larry Gibson]

Is this because of the 30-30,s relatively fast twist?

BINGO!!!!

Another fine example of a load combination exceeding the RPM threshold in a 10" twist. The tight fitting nose will be benificial to increased velocities. So will using a harder alloy of 16 - 20 BHN. A little slower powder like IMR4895 or Varget may help but I relly suggest LeveRevolution Powder with that harder bullet. Try starting at 32 gr and work up to 34.5 gr with a 16 - 20 BHN bullet.

Larry Gibson

[mainiac]

H-335 is really my go to powder in these levers,cause i have alot on hand,and it works so well in all my other guns.But i should try something slower.

This gun has the 24 inch barrell,so i envisioned alot of extra speed with this gun,but if it wont shoot tight groups,speed dont mean nothing to me.

Think a heavier boolit would counteract the fast twist?

I should make up a batch of boolits from straight lino,just to see how a tough boolit will shoot...

Larry,,whats so special about the leverution powder? Sounds intresting,,would like your thoughts.....thanks


BTW,,this is the fussiest levergun i ever fooled with.From 1400-to 2000 f.p.s.,,,there is about a foot of vertical between.If i aint paying attention to what loads im shooting,and i dont adjust the peep sight before hand,,i can be clean off the paper,@ 50 yards. Never seen so much vertical.

[Marlin Junky]

H-335 is really my go to powder in these levers,cause i have alot on hand,and it works so well in all my other guns.But i should try something slower.

This gun has the 24 inch barrell,so i envisioned alot of extra speed with this gun,but if it wont shoot tight groups,speed dont mean nothing to me.

Think a heavier boolit would counteract the fast twist?

I should make up a batch of boolits from straight lino,just to see how a tough boolit will shoot...

Larry,,whats so special about the leverution powder? Sounds intresting,,would like your thoughts.....thanks


BTW,,this is the fussiest levergun i ever fooled with.From 1400-to 2000 f.p.s.,,,there is about a foot of vertical between.If i aint paying attention to what loads im shooting,and i dont adjust the peep sight before hand,,i can be clean off the paper,@ 50 yards. Never seen so much vertical.

I've got the same rifle... could be it has a very long throat. I remedied the situation with an LBT-LFN mold. Now my range buddies call this particular rifle the 30-30 Magnum. 180 grain boolit propelled by H380 to 2400 fps and 1-1.5 MOA. That's over 170,000 RPM... RPM, SCHMAR-PM. :mrgreen:

Got a fast twist? Increase the BHN or slow down the powder burn rate so the boolit is not damaged during initial engravement. In the 30-30 Magnum's case I also strengthened the boolit by using LBT's rather unconventional cast boolit design. Now Larry's gonna tell you that there are ways to defeat the infamous RPM theory but I say it doesn't have much basis in reality if it's so easy to defeat. What we're really dealing with here is the management of shearing forces.

MJ

[mainiac]

I've got the same rifle... could be it has a very long throat. I remedied the situation with an LBT-LFN mold. Now my range buddies call this particular rifle the 30-30 Magnum. 180 grain boolit propelled by H380 to 2400 fps and 1-1.5 MOA. That's over 170,000 RPM... RPM, SCHMAR-PM. :mrgreen:

Got a fast twist? Increase the BHN or slow down the powder burn rate so the boolit is not damaged during initial engravement. In the 30-30 Magnum's case I also strengthened the boolit by using LBT's rather unconventional cast boolit design. Now Larry's gonna tell you that there are ways to defeat the infamous RPM theory but I say it doesn't have much basis in reality if it's so easy to defeat. What we're really dealing with here is the management of shearing forces.

MJ

with this lee boolit,the rifling engraves the nose of the boolit,for about.200-.250 of an inch.Real hard deep engraving.Im thinking this may be an accuracy advantage,but sucks for hunting,being that if i load the shells in and out of the gun,multiple times,the boolit is gonna be all grooved up....i guess if i had any better luck,i would only load the shell once in the gun....

Think my next trials will be with harder boolits,only place i can go,is up the hardness. I shot some 8-9 bn alloy a few weeks back,kind of by mistake.That stuff leaded my bore terrible, at no more than 1300 f.p.s.,,first time i ever leaded with a gas check boolit.these old guns are fun to play with....

[runfiverun]

waterdrop.

[Larry Gibson]

No, MJ is incorrect, I'm not going to tell you how to "defeat" the RPM threshold. He still thinks it's still some sort of "limit". It's not, The RPM threshold is just that; a threshold. Cross over it and accuracuracy goes south, just as you've found. You can push the threshold up or down ina any cartridge capable of achieving it. Exactly where the threshold is RPM wise depends on the componants and loading techniques used.

I've already given you a couple suggestions on how to raise the RPM threshold in your rifle. The way you do that is with a better designed bullet, a harder alloy and a slower burning powder. My, oh my,....but isn't that exactly what MJ did:smile: Pitty MJ can't see he's doing exactly what I keep telling him to do. He has success at it and thinks the RPM threshold is "infamous" and doesn't exist but it does, the joke is on him[smilie=s:

LeveRevolution is specially blended powder that has a very slow time/pressure curve allowing higher velocities with lower pressures. Well worth a try. It now is my "go to" powder for my softer cast 311041HPs for hunting. A safe load (within SAAMI MAP of 42,000 psi for the 30-30) is 36 gr. However, accuracy suffers a bit a the 2289 fps even with the 12" twist of the Winchester with 24" barrel. I back that off to 34.5 gr for a mild psi (several factory J bullet loads have a higher psi) and 2218 fps with excellent accuracy. Cast harder I can push to 2300+ fps and still stay within SAAMI psi and get excellent accuracy.

Larry Gibson

[Marlin Junky]

No, MJ is incorrect, I'm not going to tell you how to "defeat" the RPM threshold. He still thinks it's still some sort of "limit". It's not, The RPM threshold is just that; a threshold. Cross over it and accuracuracy goes south, just as you've found. You can push the threshold up or down ina any cartridge capable of achieving it. Exactly where the threshold is RPM wise depends on the componants and loading techniques used.

I've already given you a couple suggestions on how to raise the RPM threshold in your rifle. The way you do that is with a better designed bullet, a harder alloy and a slower burning powder. My, oh my,....but isn't that exactly what MJ did:smile: Pitty MJ can't see he's doing exactly what I keep telling him to do. He has success at it and thinks the RPM threshold is "infamous" and doesn't exist but it does, the joke is on him[smilie=s:

LeveRevolution is specially blended powder that has a very slow time/pressure curve allowing higher velocities with lower pressures. Well worth a try. It now is my "go to" powder for my softer cast 311041HPs for hunting. A safe load (within SAAMI MAP of 42,000 psi for the 30-30) is 36 gr. However, accuracy suffers a bit a the 2289 fps even with the 12" twist of the Winchester with 24" barrel. I back that off to 34.5 gr for a mild psi (several factory J bullet loads have a higher psi) and 2218 fps with excellent accuracy. Cast harder I can push to 2300+ fps and still stay within SAAMI psi and get excellent accuracy.

Larry Gibson

Larry, the problem is the RPM "threshold" is only loosely correlated to diminishing accuracy and not the cause. Understanding the actual cause of diminished accuracy is what makes one a better cast boolit handloader. I'm sure you have witnessed situations where your load was significantly below your RPM threshold and it still didn't shoot worth a darn. Similarly, we all at one point in time have wondered why a load doesn't shoot OK even though the alloy is no where near it's point of plastic deformation (e.g., chamber pressure <= .9*1422*BHN). You just can't be a good cast boolit handloader if all you look at are a couple simple minded formulas. This whole RPM thing probably got started during the wildcatters heyday because hyper velocity varmint rifles started blowing apart their thin skinned varmint bullets before reaching the entended targets. And that's all I have to say about that. ;-)

mainiac,
Engraving the boolit with too much force is generally not desirable. Knowing something about old 336's, I would make a chamber impression from the shoulder forward with a dead soft plug of lead.

MJ

[Larry Gibson]

MJ

Go back and reread the OP's 1st post. He has a good load and it is accurate until he pushes it past a certain level of RPM. The accelleration of the bullet, at the point of inaccuracy, is unbalancing the bullet in the barrel. Outside of the barrel, during flight, it is the centrafugal force at that point that is the cause of the inaccuracy of the bullet in flight. Understanding that cause then enables the shooter to mitigate, as much as he can, the adverce affects of accelleration on the bullet while in the barrel.

This can be done with a properly designed bullet, correct alloy and fit, proper lube, squarely seated GC, and a slower burning powder. However, even then this only pushes the RPM threshold upwards. At some point, if the cartridge can reach that velocity, the bullet with cross the RPM threshold and accuracy will suffer.

You can also use a slower twist. The loads I shoot at 2600+ fps out of the 14" twist .308W exceed the "point of plastic deformation (e.g., chamber pressure <= .9*1422*BHN) " by quite a bit which disproves that theory. Paper patching also disproves that theory.

If you can push that 180 gr cast bullet at 2400 fps out of the 10" twist Marlin 30-30 with such accuracy then why can't you do the same in the 30-06 you got? In reality you discovered the M70 shot best down in the 1800 - 1950 fps range but instead of understanding the real cause you assume something is wrong with the old M70......in reality your accuracywith the M70 is right at or under the RPM threshold for the componants you were using. Now as to the 2400+ fps load with a 180 gr bullet out of your 30-30 with H380 powder.....you would care to share that load data would you?

Larry Gibson

BTW; "You just can't be a good cast boolit handloader if all you look at are a couple simple minded formulas." is absolutely correct. It also applies to those who choose to disbelieve or ignore some "formulas" with out proof otherwise. Maniac's example here is a good example of proof the RPM threshold exists.Your own experiences with your M70 '06 also are also proof.

[Larry Gibson]

I really don't intend this thread to turn into another "discussion" of the RPM threshold as I am doing a CastPic article on it. However, the OP, mainiac, brought the subject up with his obvious example of the RPM threshold. MJ vehemently objects to the concept regardless of his own experiences with it. In another thread DrB asked about data, graphs or charts that i may have. Well I've gone back through some old data and charted the results of 14 different load workups in 5 different cartridges with 6 different bullets using 5 different bullets; all in barrels of 9.8 - 10" twist.

In the charted data you'll see the 2 red lines. Those are the 120-140,000 RPM range where I say the RPM threshold will generally be. In all these example you see it is. If we chart out other twist barrel's loads we will find the same range of RPM where the best accuracy is found. NOTE; I said "best accuracy". Useable accuracy, within a limited effective range, can still be found above the RPM threshold.

Larry Gibson

[Marlin Junky]

Larry,

Vehemently? That's a pretty strong description... let's just say I believe the RPM Theory has limited use; however, it is loosely correlated to more pertinent variables. I did notice from your graph that there is one function which remains relatively flat beyond 160000 RPM, though. Send me a PM describing this load and barrel configuration. Perhaps you can PM me a larger, more legible file containing your chart too. I don't want to take up anymore space on this thread. I'd like to make a suggestion or two before you publish, if I may. Find yourself a 336 in .35 Remington with an "H" or earlier date code, (and a clean barrel, naturally) scope it and test against a Remington rifle with a hammer forged barrel possessing equivalent twist and length. Shouldn't be too hard to find these two test platforms. Hopefully the difference in groove diameter and chamber dimensions won't be a problem... right there is one variable (chamber dimensions) that is very difficult to control unless you're cutting your own chambers. You can "factor-in" the difference in inherent accuracy between the two firearms platforms by giving the lever action a 1/2 MOA handicap. Actually, why not just buy two 336's in 30-30! One made with a date code of "G" or "H" (stay away from the "F" date code guns because of the possible "Magnum" chamber) and one with MicroGroove rifling? Actually, that won't even work because of the difference in bore diameter... hey, testing is hard! :-D To provide more credence to your analysis, start with no preconceived notions about RPM Theory... just shoot the two guns and report velocity, group size, pressure (you do have that capability, don't you) and RPM. Then we can all draw conclusions about which is more important: firearm attributes and design or calculating how fast the boolit spins down range. Don't forget to measure BHN and always use the same boolit mold... wow, that's even hard because of chamber variation vs. boolit fit!... I'm glad I'm not doing this... sounds too much like work! Please allow me to suggest an LBT-LFN 358-210. Then you can start all over again with an RCBS 35-200-FN that'll drop a .360-.361" boolit (you might need to call RCBS but I bet they'll accommodate you).

Looking forward to a legible version of your chart.

Thanks,
MJ

[Char-Gar]

I don't want to get into the RPM discussion, but I will only say that with both Marlin and Winchester leverguns, I get excellent accuracy, (2 MOA or less) at 2,100 fps. The charge is 29/3031 and an appropriate bulelt (fit wise) for each rifle of a nominal weight of 170 grains (gas check of course). The alloy is Lyman No. 2 at about 15 Bhn.

The Marlin is a 1972 336A and the Winchester is a 1951 Model 94 Carbine. I also get the same result in a Savage 340. I also have a Browning Traditonal Hunter SS in 30-30 and accuracy with that rifle and above load runs 1 MOA or slightly less. I use 311467 in the Browning.

The bullets are SAECO 325 in the Marlin, 311291 in the Winchester and Savage, and there are several bullets (311291, 311467, RCBS 165 Sil) that do well in the Browning. Of course, each bullet is a proper fit to the rifle.

I am pushing hard up against age 70, so am getting leery of my memory, but IIRC the Marlin twist if 1-10 and the rest are 1-12.

I have no problems pushing cast bullet past 2,000 fps with good accuracy in my numerous .308s and 30-06's, Some of the .308s are 1-12 and one is 1-10. The 30-06s of course are all 1-10.

I certainly won't claim to have the depth of scientific knowledge that some here have, but I do have many years of trigger time and many, many targets fired with various 30 calibers rifles and cast bullets. All I know is what the targets tell me.

[mainiac]

All i can really think about is my J model marlin in 32 special.This gun will shoot groups@ 50 yards well under .5 inch,,on demand,and it will do it @ 2270f.p.s. with the rcbs boolit.

I want this F model 30-30 to shoot as well.Thats what im gonna strive for.

I have considerable past experience with benchrest rifles,and with them,the barrell twist is right on the verge of not enough,and thats where they shoot the best.So,I think it all boils down to is the slowest twist possible shoots the tightest groups.Over twisting puts tremendous stress on a jacketed bullet,so i can just amagine how the cast pill feels.

[NHlever]

Shooting, especially with cast bullets is lots of fun, and a very learning experience. I've been casting, and shooting for about 50 years now, and it has been both fun, and interesting to see the changes in our craft over the years. If one reads the earliest Lyman cast bullet manuals he can see how much of it was almost witchcraft at that time. Things like boolit fit in the throat, alloy, etc. weren't understood very well. We are doing things today that were unheard of back then routinely, and yet certain truths can't be ignored. When the forces acting against a boolit exceed the strength of the alloy the boolit is made of, the boolit is damaged to one extent, or another. Damaged boolits don't group as well as undamaged ones do. We can call this truth by any name, and often it is called different things by different folks here but the results are the same. It is not some theory that needs to be proven, or defended, it is just one of the facts that we work with in our quest for ever better results.

[northmn]

I get factory velocities in my Marlin using a 188 grain (cast weight) Lee bullet designed for the 303's sized down to 310. I use a flat nose punch for sizing. I water harden the bullets after sizing and soften the nose for hunting bullets by placing them in a shallow pan of water and annealing the noses. They are harder than WW and shoot pretty fair.

DP

[Char-Gar]

mainiac.. Do not forget the 32 WS comes with 1-16 twist barrels. You have work hard to find a cast bullet load that will not shoot well in them.

The 30-30 with its 1-10 or 1-12 twist barrel will shoot cast bullets very well, do not use a 32 WS as the gold standard for 30-30s. They are two very different critters!

Shooting cast bullets in a 32 WS will spoil you very quickly with their cast bullet accuracy.

When I got my 32 WS (a 1959 Winchester 94 Carbine) I loaded up some ammo with the RCBS 170 GC bullet and 30/H-335 and went to the range. My first group like yours was 1/2 inch at 50 yards and the velocities were full snort. Easiest cast bullet accuracy load I have every found.

[mainiac]

mainiac.. Do not forget the 32 WS comes with 1-16 twist barrels. You have work hard to find a cast bullet load that will not shoot well in them.

The 30-30 with its 1-10 or 1-12 twist barrel will shoot cast bullets very well, do not use a 32 WS as the gold standard for 30-30s. They are two very different critters!

Shooting cast bullets in a 32 WS will spoil you very quickly with their cast bullet accuracy.

When I got my 32 WS (a 1959 Winchester 94 Carbine) I loaded up some ammo with the RCBS 170 GC bullet and 30/H-335 and went to the range. My first group like yours was 1/2 inch at 50 yards and the velocities were full snort. Easiest cast bullet accuracy load I have every found.

char-gar,,thats what happened to me with my 32. I have never really spent much load work time with it.I used h-335,and kept turning up the wick until the gun started to be painful,and the hotter i load it,the better it shoots.Ive tried a few powders,but come back to 335,and the gun shoots such pretty tiny groups,,its so simple

Guess this thutty-thutty,is gonna be my pay back.

[Char-Gar]

The 30-30 is not a difficult nut to crack as it is one of the better cast bullet rounds. You are just going to have to work for what you get. The 32 WS gifts us with accuracy, the 30-30 isn't so generous.

[Marlin Junky]

After looking at the pic of your chamber casting, I'm going to recommend a 150 grain LBT-LFN. I would send a chamber casting to Verl Smith too... especially if you can create a little better filled out one. I don't think your freebore is long enough to handle the 180 grain LBT-LFN; however, you should be able to get some pretty spectacular results with a 150-155 grain LBT-LFN.

MJ

[JIMinPHX]

I've found that I get my best hi speed cast .30-30 accuracy with RE7. That was using a 150-grain Lee RNFP. I haven't tried the 170.

[Marlin Junky]

I've found that I get my best hi speed cast .30-30 accuracy with RE7. That was using a 150-grain Lee RNFP. I haven't tried the 170.

The Lee 150 may work for him but it should cast .311" on the bands and .301" on the nose. The nose diameter isn't as critical on the 150 as on the 170 because of the shorter length of the former's nose; however, it should cast as close to round as possible. I have a Lee 309-170 that actually is one of the best molds I have for my M70 in 30-'06. Fit is King.

MJ

[JIMinPHX]

I'm sizing mine at .310" & getting full clean up on the driving bands. I haven't measured the nose diameter.

[1Shirt]

Never had bad advice from Larry Gibson. He is one of a half dozen or so on this forum that I really pay attention to and appreciate. His threads are well thought out and well written.
1Shirt!:coffee:

[Marlin Junky]

The main problem I have with Larry's (and he'll say it's not his) RPM threshold is that it's too simplistic. I don't know if this has been discussed before; however, without considering the boolit's inertia, using RPM alone provides limited insight into what is physically happening as the boolit accelerates down the barrel. I've got more testing to do before establishing the following as my guidelines; however, I believe a more meaningful parameter would be obtained by multiplying the boolit's SD (sectional density) by its RPM. There must be a trade off somewhere between inertia and bearing length but when I jumped from 300 to 345 grain boolits in my 444, (20" twist) I really needed to start shooting harder alloy in order to maintain the same level of accuracy. I'm not saying that SD*RPM is the answer to all my problems because it doesn't incorporate the all important acceleration variable.

Larry, if the booilts inertia is something you've considered before, then my hat's off to you. Frequently, I simply don't have the time to analyze your entire posts. Try to be more pithy. ;)

Good Shooting,
MJ

[Larry Gibson]

The 30-30 is not a difficult nut to crack as it is one of the better cast bullet rounds. You are just going to have to work for what you get. The 32 WS gifts us with accuracy, the 30-30 isn't so generous.

As already mentioned; the difference is a 16" twist of the .32 vs the 10 or 12" twists of the 30-30s.

Also I've no problems with "good accuracy" over the RPM threshold. The question is where does the "best accuracy" come? Also, I'm sure you've found, that beyond "good accuracy" very poor accuracy comes rather quickly.

Larry Gibson

[frnkeore]

This data was shot in my 340 Savage 30/30 with a 12 twist, 22" barrel but should work in any 30/30.

34.0 gr WC852F
F210 primer
311291 bullet
2130 fps
10.2 fps SD
26 fps ES
1 1/4", 5 shot group @ 100

Frank

[Larry Gibson]

MJ

Yup "testing is hard". I don't need to get 2 other Marlins as I've shot numerous of them and the RPM threshold applies to all of them in 30-30 whether 4 groove or Micro-groove. The .35 Rems you suggest have twists that you can not safely exceed the RPM threshold with safe loads using RCBS 35-200-FN 200 gr cast bullets or the other one for that matter. Your concept of that test would not then be valid now would it?

Too bad you can't read the graph. PM me your email address and I'll email the full size copy. You'll note on it the the graph represents loads fired in 5 seperate rifles all with the variances you suggest would alter the results if I only used the 2 Marlins you suggest. Thus those "variances" are already there. The graph represents loads fired with "no preconceived notions about RPM Theory... just shoot the two guns and report velocity, group size, pressure (you do have that capability, don't you) and RPM." and "vehemently" do demonstrate the point. besides the different rifles and cartridges used there are also 5 different powders, 3 different alloys and 6 different bullets sized to the particular rifle, different psi's (yes, I do measure them) represented. Lots of "variances" eh? And the end result is well represnted between the 120 - 140,000 RPM level isn't it.

"I did notice from your graph that there is one function which remains relatively flat beyond 160000 RPM, though. Send me a PM describing this load and barrel configuration."

I'll post it here; that load is from the tests that Bass Ackward and I did with the "ill fitting" 311291 bullet that 45 2.1 complained so much about. The load was in fire formed, NS'd WW Super '06 cases. Primers were WLRs. Powder was RL19. Alloy was WWs + 2% tin WQ'd. Bullet was sized at .311 with a Hornady GC and Javelina lube used. Rifle is a M98 BRNO action with a 24" heavy sporter barrel with 6 land rifling. The chamber was cut with a match reamer to minimum SAAMI headspace specs. Twist is 1-10". Even though I managed to get "good accuracy" of 2 - 2.5" ten shot groups at 100 yards with it at 2200+ fps/158,000+ RPM you notice that "best accuracy" was still uder the RPM threshold at 1750 - 1800 fps/125-130,000 RPM.

The above load pushed the RPM threshold with useable "good accuracy" because the "ill fitting" bullet actually did "fit" contrary to what 45 2.1 complains about. A slower burning powder was also used to lesson the adverse affects of accelleration on the bullet. Both are atypical of the things i always suggest to use to pushed the RPM threshold. A better designed bullet such as Bass's LBT bullet or the Lyman 311466 I use allow even higher velocity/RPM to be obtained with "good accuracy".

In 10" twist rifles whether the 30-30, .308W or the '06, for example, the bullet won't care what configuration the barrel is or what cartridge it was when in flight. The cause and effects of exterior ballistices will effrect the bullet the same regardless.

It remains the same that the OP here is exceeding the RPM threshold with that load in his 30-30 Marlin with 10" twist at right about 1850 fps. That is why the accuracy goes south for him, just as he suspects.

Larry Gibson

[Larry Gibson]

This data was shot in my 340 Savage 30/30 with a 12 twist, 22" barrel but should work in any 30/30.

34.0 gr WC852F
F210 primer
311291 bullet
2130 fps
10.2 fps SD
26 fps ES
1 1/4", 5 shot group @ 100

Frank

Looks like an excellent load for a 12" twist 30-30 to me:bigsmyl2:

Larry Gibson

[Marlin Junky]

I don't need to get 2 other Marlins as I've shot numerous of them and the RPM threshold applies to all of them in 30-30 whether 4 groove or Micro-groove. The .35 Rems you suggest have twists that you can not safely exceed the RPM threshold with safe loads using RCBS 35-200-FN 200 gr cast bullets or the other one for that matter. Your concept of that test would not then be valid now would it?

Larry, have you honestly ever done load development with a pre-55 336, especially a 7-groove .35R? My point was not too exceed 140,000 RPM with the .35 Remington cartridge, but to compare the accuracy results obtained using the two different barrels with the same twist and load as you approach the "threshold" as you call it (even in your own arguments, sometimes it's a threshold and other times it's a finite boundary). You are closing yourself off to many variables... and I just gave you some credit above for trying to measure things. OK, lets take the following approach. My hypothesis is, (with respect to the .35R experiment) the old Marlin is going to kick the Remington's butt past 2200 fps in the accuracy department given the same barrel length, load and twist. What do you think will happen in a side by side shoot off and why?

MJ

[Marlin Junky]

Originally Posted by frnkeore:
This data was shot in my 340 Savage 30/30 with a 12 twist, 22" barrel but should work in any 30/30.

34.0 gr WC852F
F210 primer
311291 bullet
2130 fps
10.2 fps SD
26 fps ES
1 1/4", 5 shot group @ 100


It'll work just as well with an actual Ballard rifled 336 with BHN 15 metal and a 10" twist (and iron sights).

MJ

[Marlin Junky]

In 10" twist rifles whether the 30-30, .308W or the '06, for example, the bullet won't care what configuration the barrel is or what cartridge it was when in flight. The cause and effects of exterior ballistices will effrect the bullet the same regardless.

Larry Gibson

Exterior ballistics!?... now we're not even on the same planet, again... I give up.

I was going to let sleeping dogs lie, but if this whole RPM thing of yours revolves around boolits/bullets spinning in air, (exterior ballistics) how the heck did you derive the 140,000 figure and how do you explain fragile little .22 bullets spinning at over 200,000 RPM with the ability to center-punch ground squirrels at 300+ yards? I've been trying to adapt the concept of RPM to something useful for cast boolit shooters relative to destructive internal rotational forces. If you're pounding an RPM drum because you think the number of rotations a boolit completes in air, beyond some arbitrary figure, will make boolit accuracy go to heck, then our domains will never intersect, so to speak. Get real, get inside your barrel. :wink:

Good night,
MJ

[Larry Gibson]

MJ

Without being "pithy", might I suggest a better understanding of ballistics on your part might be in order to get you back on planet Earth;)

In any barrel you can accellerate some pretty bad or good bullets the length of the barrel and guess what? They will all follow the exact same path as defined by the bore. Given the same velocity they will all have the same RPM on exit. Inside the barrel their "accuracy" will be identical whether they are good bullets or horrible bullets. It's what happens during flight the the RPM affects both in stability and accuracy.

There are 3 distinct parts to ballistics; internal (that's inside the barrel), external (that's the part where the bullet is in flight) and external(that's the part where it hits and penetrates the target). Until you get "out of the barrel" you will never have a "real" understanding of what the subject is.

Larry Gibson

BTW; I have never said The RPM threshold is a "finite boundary". Also the "destructive internal rotational forces" you mention have nothing to do with the RPM threshold. They are another issue altogether. And those "" have a metal jacket around them, that's how. So I'll just not waste any more time here ..............[smilie=b:

[OnHoPr]

I don't want to hijack or got off topic, but I'm less experienced in the CB doctrine than most of you here. I've read Lyman 3rd edition, Lee 2nd edition, LASC, and a number of threads on cast boolits and trying to gather info with comprehension. I been wanting to ask a question about this RPM theory, but have found it difficult to do so, because of the inexperience of CB characteristics. I would like to ask a prelude question though. Is there a base line type format of this concept, such as Lyman No.2 alloy with a medium published load of IMR 4895 with your average 170gr boolit in a 1 in 10" twist? Thanx

[Larry Gibson]

OnHoPr

"I been wanting to ask a question about this RPM theory, but have found it difficult to do so, because of the inexperience of CB characteristics. I would like to ask a prelude question though. Is there a base line type format of this concept, such as Lyman No.2 alloy with a medium published load of IMR 4895 with your average 170gr boolit in a 1 in 10" twist? Thanx"

Very good question;

Look closely at the chart I posted and you will see that best accuracy with that combo or a similar combo will fall into the 1750 - 1950 fps range or the 122-140,000 RPM range. You can push that higher to 2000-2100 fps and maintain very useable accuracy with slower powders or a larger volume case than the 30-30 with much slower powders. However, at some point close to, within or slightly above that velocity/RPM level, non-linear exapnsion of groups size as range extends (best measured with 8-10 shot groups at 100 and 200 yards) will occur indicating the load has crossed its RPM threshold.

Basically if you are talking a 30-30 with a 10" twist then best accuracy will be in the velocity/RPM range mentioned with a #2 alloyed GC'd cast 170 gr bullet and a medium load of 4895. 30-30s with 12" twist barrels can get best accuracy in the same RPM range but the velocity will be higher, in the 1950 - 2200+ fps range.

Larry Gibson

[geargnasher]

OnHoPr, seems pretty on-topic to me. Larry and I disagree on some of the causes of the RPM theory (a point not pertinent to this particular thread), but I certainly don't disagree that the phenom exists as I've consistently observed the same thing, and even gone back over old targets and figured RPM vs. group size just to see. Most of my best loads were and are within the window he specifies. It's a pretty decent guideline for accuracy loading with regular cast, grease-groove boolits, worth paying attention to.

As far as a "base line format", all I can say is that typically loads I've tried that SHOULD shoot well because the powder burn rate, charge, alloy, primer, case prep, lube, and gun condition are all good and balanced for the desired velocity usually start to degrade in the velocity department around 140-150K RPM. Certain extreme measures can extend this considerably, but it's dicey even then. Essentially, Larry has shown a correlation between twist rate and MOST accurate velocity, and THAT is the baseline here, since so few other factors (powder, lube, exact alloy) affect the accuracy of an otherwise "correctly" assembled load so consistently.

Gear

[rintinglen]

To wander back to the original topic, I like the 311-291 over 33 grains of WW-748 and the 311-041 over 34 grains of WW-748. I have also used IMR 4895, surplus 4895, and 3031 with success, success meaning equal to or better than factory Remington boolits. I have 5 30-30s and for a time was going through 400 rounds a month. I also like the 30-180 FN that RCBS makes, 28.5 grains of WW-748 and 17.5 grains of 2400 work well for me, but the long Nose may be problematic in some guns.

[Larry Gibson]

rintinglen

What make are the five 30-30s?

Larry Gibson

[mainiac]

gun is shooting pretty well now.I finally got a boolit that is fat enough,only trouble is that now i dont have neck clearance,so have very stiff chambering,as a result. Resorting to neck turned cases to ease the chambering.

Found out this gun loves slow burning powder. AA3100 makes the gun shoot under inch groups,and h414 is looking good as well. I toughened up the boolit,run a fatter one,and use slow powder,and the gun is starting to be happy!

It may shoot as well as my .32 special,,in time.One can only hope!

[OnHoPr]

I would like to add another prelude question while this info is swirling around in the ole noodle. Does the length of the boolit come to play in the RPM theory or at least be considered? Such as for example, take the j's .22 cal. 50gr likes the 1 in 14" twist compared to the heavier 75gr which likes the 1 in 8" or 9" twist. Correlate the previous statement with the .30 cal 150gr range and the 200gr range boolits. All these considerations are getting a little more complicated, especially for shooting a doe on public land, but it is interesting.

[Larry Gibson]

OnHoPr

Rate of twist required for for stability has nothing to do with the RPM threshold. The RPM threshold is how, at a certian level of RPM, the accuracy is adversely affected by the centrafugal force actiong adversely on the imbalences of the bullet in flight.

Larry Gibson

[Nrut]

OnHoPr

Rate of twist required for for stability has nothing to do with the RPM threshold. The RPM threshold is how, at a certian level of RPM, the accuracy is adversely affected by the centrafugal force actiong adversely on the imbalences of the bullet in flight.

Larry Gibson
So if you have a perfectly balanced bullet exit the barrel squarely at say 250,000 rpm's there would be not accuracy problem due to centrifugal force?
Is that correct?

[frnkeore]

Is the strength of the bullet a limiting factor? Such as 40/1 as opposed to Linotype. If so, what would be the correction factor?

Frank

[dualsport]

This data was shot in my 340 Savage 30/30 with a 12 twist, 22" barrel but should work in any 30/30.

34.0 gr WC852F
F210 primer
311291 bullet
2130 fps
10.2 fps SD
26 fps ES
1 1/4", 5 shot group @ 100

Frank

Pardon my hijak but isn't AA2700 supposed to be a reproduction of WC852, used for GI M2 30-06 ammo? Or am I remembering that all wrong? I'm going sideways with this while you guys focus on rpms but I have a lot of AA2700 and never thought of using it for full loads in a 30-30. Could be interesting. I'm thinking actually of the Saeco #315 in a M94.

[frnkeore]

I have both WC852 and WC 852F. I've never used AA2700 but, I would like to know if it's the same as 852. My 852 burns much like H4831 or H450 in my '06, 6mm and 22 CHeetah with jacketed loads. I use a load of 46.0 in my 8x57 with a 200+ bullet but, thats been the only cast load i've used with it.

The 852F burns like H380 in my cast loads and that was what they said it would burn like. I haven't used it in jacketed.

Frank

[Larry Gibson]

So if you have a perfectly balanced bullet exit the barrel squarely at say 250,000 rpm's there would be not accuracy problem due to centrifugal force?
Is that correct?

That is correct.

The trick to accuracy at HV with cast bullets is to mitigate imbalances to the bullet during accelleration while in the barrel. That is in addition to casting a ballanced bullet and keeping it balanced during sizing, seating of the GC, during loading and keeping the bullet concentric to the throat and bore curing chambering. All can be a daunting task. Additionally we can mitigae imbalances to the bullet during accelleration by using a bullet of proepr design and fit to throat/bore and the use of slow burning powders to lesson the time/pressure curve.

The lessor or smaller the imbalances in the cast bullet are the less the centrifugal force will have to act upon, thus the higher the RPM/velocity must be to cause inaccuracy from the bullet either departing from the line of flight in a helical arc path. A perfectly balanced bullet during flight leaves nothing for the centrifugal force to act upon because the centrifugal force is exerted equally in all directions.

Larry Gibson

[OnHoPr]

Larry Gibson

Its kinda hard to read your chart on page 1 with my eyes and this computer thing. But, in reference to the chart I would like to ask is the first charted line that stops at 3.6" at 1930fps the 5744 test? Also, the charted line that goes off the chart at 2.8" at 2240 the rel 19? Thanx

Another point to bring up is do the faster powders have a smaller window for optimum accuracy compared to the slower powders with a possible larger window? To where as .5gr increments could be used on the faster powders for testing to try and find the sweeter spot. I usually test at 1gr increments, but with powders slower than 4895. I haven't found any powders faster than the 4895 that have been suitable really unless they were below published start grains.

[Larry Gibson]

OnHoPr

Quick answer as I'm out of town and pretty busy on a work project I got talked into....sorry.

The "window" powders will have is dependent on the where the burning efficiency of the powder with that load and bullet weight begins and ends when it grosses the threshold for that load. Can be larger with some powders, smaller with others and not at all with some.

Yes those charted lines referred to are correct.

Have to agree the published "start loads"for faster powders are most often too high to begin with. Also many medium and slower powders do not begin to burn efficiently with lighter weight bullets until after the RPM threshold is passed. That's the problem with "published data" that relies on internal ballistics only to derive "accuracy" loads.

Larry Gibson

[OnHoPr]

Thanx LG for the info. As I'm getting older and slowing down a bit, I was thinking of getting into Hunter Class BR for starters. I went to a monthly shoot at club and those targets are pretty small at 100 and 200 yards at least to group or score. A lot smaller than a deer. I am trying to get enlightened in this particular form of shooting and there is a lot of info to digest. I haven't even started my lube, alloy, throating, etc., and etc. home schooling classes yet. Again, thanx.:coffeecom

[frnkeore]

Larry,
Could you scroll up to post #42. I was wanting your oppinion on my question on bullet strength.

Thank you,

Frank

[Larry Gibson]

Is the strength of the bullet a limiting factor? Such as 40/1 as opposed to Linotype. If so, what would be the correction factor?

Frank

I hesitate to use the work "limiting" because some in particular then want to think the RPM threshold is a Limit" which it is not. In context with your question how ever the answer is yes with some caveats. With a faster powder such as 2400 a softer alloy will have a lower RPM threshold than if 4895 is used or if 4831 is used. The slowerthe burning rate of the powder the slower the time pressure curve is with less uneven obturation, setback or sloughing of the bullet during accelleration. That means the bullet will maintain its shape and balance better. That means a better balanced bullet during flight with a higher velocity/RPM obtainable before the adverse affects of the centrigugal force become apparent as the bullet crosses the RPM threshold.

Harder alloys that are more malleable than linotype are better when shooting at HV, even those with a slightly less BHN. Linotype has a high antimony content and can be brittle. Depending on bullet design small parts of the driving bands can chip or break off from the rifling during accelleration. This, of course un balances the bullets. Also bullets with high antimony can have hard and soft spots which can cause uneven setback, obturation or sloughing during accelleration. Used to be it was believed only a reallyhard cast bullet could be shot accurately at high velocity. However, many of us have found otherwise. even setback is the probable reason why.

Larry Gibson

[Centaur 1]

I'm reading a lot of numbers being tossed around in this discussion about RPM threshold, perhaps a better explanation could be expressed by using surface feet per minute instead of RPM. SFM is calculated by multiplying the projectiles circumference (diameter x Pi) by RPM, then dividing by 12. Anyone who's ever run a lathe knows that a larger diameter workpiece needs to be turned at a slower RPM. Ideally the machinist adjusts the RPM's so that the same amount of surface feet are cut by the tool bit. As an example there was mention of .22 caliber varmint bullets rotating at 200,000 rpm's without any difficulties. .224@200,000rpm's=11,728s.f.m., this is almost identical to a .308@144,000rpm's=11,611s.f.m. I don't know if this is the answer, but I believe that there's some relevence.

[ammohead]

Went out today with a 1898 yom model 94 winchester with dark but sharply defined rifling. I loaded 15 gr of surplus 4759 under a noe group buy 311466 at 18 bhn. After playing with the rear sight a little I shot a .888 3 shot group at 50 yards. And I don't even know what the twist rate is much less the rpm or sfm. Burned up the rest of the rounds plinking at a bowling pin at 200. Fun stuff.

ammohead

[popper]

LG is correct. Math for gyro action is simplified here. http://www.cleonis.nl/physics/phys256/gyroscope_physics.php Gravity is also an unbalancing force. nutation is why the groups spread, instead of just going one direction. It also explains why groups open up at larger ranges. Eventually, tumbling occurs. As we cannot measure terms for the equations easily for each bullet, we do empirical testing. Is shear strength of the bullet important - yup. Cast em. load em shoot em and see the results.

[mainiac]

Well,i got the gun shooting groups under an inch,@50 yards,and doing over 2100 f.p.s. to boot!
Maybe there is hope in this ol girl afterall.Using a fat boolit,(i have to neck turn my cases in order for them to chamber) and bn of about 19,and using real slow burning powder,,,,now she wants to be a shooter.

[pls1911]

I have several 1936 through 1952 Marlins similar to the subject of this thread.
Throats longer than those found in later microgroove barrels are the norm.
The trick for great accuracy with these pre microgroove barrels is moderation:
Reloader 7 at 25-26 grains pushing either a Ranch Dog 165 or Seaco #136
(about 163 grains), sized through a .312 die is the trick for great accuracy without leading.

THE KEY:
1. I cast soft... about 75% lead ( free) to 25% wheel weights (getting scarce) ; this gives aboit 10-12 bhn, and trace elements for:
2: Haeat treat HARD... in the oven at 450 degrees for an hour, and into an ice water quench... this gives about 25bhn. The alloy is hard enough to be shot at 1800-2000 fps, and retains maleability to flow at impact instead of shattering.
I lube and set the gas check with whatever's in the luber, then lube again lightly with JPW/LLA.
Good groups in many guns including microgroove have been the result, and I'm not too fussy about OAL so long as it feeds through the action.