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Thread: The Components of Going Faster

  1. #101
    Boolit Master

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    So, baby steps.

    Got the 24", 1-10", CZ .30-06 to the range yesterday for my first .30XCB experiment using H4831SC and 2500+ lube. Bullet alloy was 1 part Lyman #2 to 2 parts linotype at about 19BHN. Lapua brass. Primers were Federal Gold Medals. Empty space in the case loosely filled with Dacron.

    Starting charge was 38 grains and worked up in steps of half a grain. Three shots fired for group at each step over an Oehler 35P. Nine shots fired, then the barrel was allowed to cool back down to "room temperature" (a fairly cool, windy day in the '60's).

    For the less intense 38 to 46.5 grain charges, we used our "2nd quality" bullets with the lumpier sprue cuts. These took us from a 3-shot average of 1754 up to 2222fps. Worth noting is that combustion of the propellant was not really complete until we reached 43 grains. Prior to that, there was a significant trail of unburned granules left at the 6:00 position of the bore. None of these loads had trouble staying in the 6" 9-ring diameter of an SR-1 target and we had numerous instances of two in one hole, and plenty that would hold the 3" 10-ring.

    We hit the pretty-based "1st Quality" bullets at 47 grains. Best group for the day was about 1.5" inches at 2267 fps with the 47.5 grain charge.

    The wheels started to come off the wagon shortly thereafter. 50 grains took us to 2374 fps and it was decided that accuracy had left the building. At 51 grains and 2415 fps, we experienced the first bullet completely off the 10" SR-1 repair center. 52 grains got to 2481 fps, were spread out at over a foot. Metal fouling was beginning to appear on the crown over the last several groups. There was an impact mark from a gas check on one of the chronograph's sky screens, so definitely experiencing some of the previously-discussed integrity issues

    We were intrigued enough by the lower speed accuracy and the earlier results from Dad's '95/Krag to heat treat and water quench some of the older WW+2% versions of the bullet. Going to run these from about 46 to hopefully 58 grains to see what transpires. Next range adventure hopefully in a few days.
    WWJMBD?

    In the Land of Oz, we cast with wheel weight and 2% Tin, Man.

  2. #102
    Boolit Grand Master popper's Avatar
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    same total amount of acceleration - but that is not what counts except for muzzle fps. F=m*A and F comes from psi and base area (dia) of bullet. So, A is proportional to psi curve. A= (psi*pi *r*r)/m.
    Metal fouling ... beginning to appear on the crown. Definite leading! I get some in the BO linear comp. Lead scraping by the GC and HV 'dust' exit from muzzle (calculated muzzle gas exit fps is 10-20% greater than the bullet fps -bernouli effect)? I only recovered one GC and it was dished so I assume, as the edges are stiffer than the center, the edges get twercked outward adding to the scraping effect. And possibly loosening the GC.
    My rifle moulds are effectively smooth sided, just a small groove for collecting displace alloy and about half way in the drive band (drive band is approx 1/2 - 3/4 of bullet length). They shoot fast and well. I did put one coat of BLL on some, no difference I could tell. I have some only BLL'd to compare in 308W yet. Shot 2 coats BLL in BO GCd and results were good, compared to PC, both in 18-1900 fps range. 2400 may be different. BLL doesn't get pumped from a groove but may also have a layer effect.
    Last edited by popper; 04-25-2022 at 03:30 PM.
    Whatever!

  3. #103
    Boolit Buddy
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    Quote Originally Posted by popper View Post
    same total amount of acceleration - but that is not what counts except for muzzle fps. F=m*A and F comes from psi and base area (dia) of bullet. So, A is proportional to psi curve. A= (psi*pi *r*r)/m.

    Acceleration is the derivative of the psi curve. The rate of acceleration is greatest at peak chamber pressure. There might be some slow rate of acceleration that is too slow to pump a given lube groove, but it is likely at points in the graph below 5-15k psi depending on lube groove design. Outside of these low pressure times and locations on the graph, if you add up all the time under the curve it will give you a total amount of lube groove pumping acceleration in a load.

    On two loads that both reach a given velocity but with different peak pressures, they will have the same amount of total acceleration above the cutoff PSI (where psi is too low to pump the lube groove) and therefore the same amount of lube groove deformation. The difference is that the lower pressure load pumps its lube out slow and steady as it travels down the barrel and the high pressure load pumps the lube harder and sooner and pressurizes the lube too much, squirting it past the nose of the bullet early in the barrel and making the bullet undersized as it rides on its lube gasket. Then the bullet runs out of lube too soon in the barrel because it was flowing in front of the bullet instead of wiping on the barrel as the bullet goes past.

    Have you ever recovered any of your small displacement groove bullets after firing? I bet the groove gets deformed at least 50% meaning at least some of the tumble lube in there would be pumped out. I have only been experimenting with TL and PC because I have some mold designs with weak lube grooves and small base bands that like to scrub the PC off the base band with high pressure loads. We have seen time and time again that only the tiniest amount of lube is needed if you are using anything modern other than mutton tallow and frog skins. If your small groove is placed to where it moderately deforms at the pressure you commonly shoot, it will probably shoot great and give your PC a free ride for at least the first half of the barrel, leaving it in better condition at the crown leading to less PC fouling in the comp. The small amount of lube fouling will be easier to clean than baked on vaporized PC.

  4. #104
    Boolit Grand Master popper's Avatar
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    Have you ever recovered any of your small displacement groove bullets after firing?
    Nope. They are PC'd and the groove is there to collect alloy from barrel sizing and lands. I load near max in the rifles, have a PB of similar design I've pushed to 2k fps in 300 BO, MOA at 100. Objective was to eliminate the 'tail' at the base from all the moved alloy. Seems to work fine.
    Yea, I tried to give a simplified version of the equation.
    It's interesting if you play with GRT or QL, slow powder doesn't (normally) completely burn but fps increase is very low toward the muzzle. Wasted powder but it won't burn right if you 'short it' of powder, pressure isn't high enough for good burn. One 'solution' is a heavy for cal. bullet (momentum) to get burn eff. up and hard crimp.
    easier to clean than baked on vaporized PC - PC isn't baked on, dissolves with solvent, the hardened lead/powder residue is tougher.
    I have recovered some 40sw and the normal lube groove on them didn't appear to be collapsed much. They were coated, not lubed. Did have some base 'tail'. They were shot into a rock pile, 98% retained weight and the coating was pretty much removed from the sides AND nose (TC design)! Nose was close to body dia. so assume the coating there fractured from impact. Coating left on the body had turned white - coating was green.
    Last edited by popper; 04-26-2022 at 11:04 AM.
    Whatever!

  5. #105
    Boolit Grand Master


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    Here's 5 recovered XCBs from soppy wet newsprint at 300 yards. Velocity from the 30x60 XCB was 2900 fps at muzzle. The bottom bullet is an as cast 30 XCB with just the GC crimped on. The 30 XCBs are sized. ,310 before loading. Note little if any collapse of the lube grooves on any of the recovered bullets as compared to the "as cast" XCB. No gas cutting is seen on any of the 5 bullets. The two recovered GCs show no alloy melting given 2900 fps at 50,000 psi.

    The recovered diameter of each bullet;

    A. .3061
    B. .3063
    C. .3062
    D. .3065
    E. .3065

    The unfired "as cast" XCB is .311

    Click image for larger version. 

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    With a properly designed bullet for the task such as the 30 XCB cast of a proper alloy we see how well the bullet holds up to the higher pressure (50,000 psi) needed for the velocity.
    Larry Gibson

    “Deficient observation is merely a form of ignorance and responsible for the many morbid notions and foolish ideas prevailing.”
    ― Nikola Tesla

  6. #106
    Boolit Master

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    Pop & I did a rocket run to the range yesterday afternoon after I got off work to get a last bit of "SCIENCE!" in before a forced 3-week break (vacation). Gonna need to look hard at the chrono data, but for water quenched WW+2% out of a 1-10" twist, Chuck Yeager's "demon" seems to be living around 2,300 fps and 53 (ish) grains of H4831SC.

    The encouraging bit in there was we did an abbreviated ladder workup string of six rounds across three grains of powder all went into about 3 MOA, so at least once we figure out where the failure point is, there's plenty of space to work further down.

    Getting the lead vapor deposits at the crown despite the 2500+ and a nose-dip of BLL, but in spite of that, the bore itself seems to be running very clean.
    WWJMBD?

    In the Land of Oz, we cast with wheel weight and 2% Tin, Man.

  7. #107
    Boolit Master
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    Larry, have you ever seen anything written about bullets being smaller due to the lube layer? I have not. Have you discovered something no one knew about?

    Just curious, can you measure the dia of the bullets in the nose section, as far forward as you can and just in front of first lube groove?

    PS did you have to remove those GCs from the bullets or did they separate after entering the bullet stop?

    Sorry, last one. What dia are the GCs on the bullets?

  8. #108
    Boolit Master

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    More theory on gas check separation:

    Both copper and lead are getting squeezed equally by barrel and our mysterious "lube force", and there is the possibility of bullet bases getting melted under the gas check.

    Springback is going to be greater on copper than lead, and its affect is most likely to be seen at the front edge of the gas check. If its grip on the bullet has been compromised by compression and liquefaction at the rearmost corner, that front edge is our last remaining point of contact, and now it's gone.

    So on the one hand, I'm now thinking that annealing gas checks to render them as dead soft as possible may be a key part to this. On the other hand, I wonder if, due to the pressures and heat involved at these high speeds, if the gas checks are getting flash-annealed in the bore and this theory is much ado about nothing.
    WWJMBD?

    In the Land of Oz, we cast with wheel weight and 2% Tin, Man.

  9. #109
    Boolit Grand Master


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    charlie b

    Apologies for the late response, just saw the post.

    Larry, have you ever seen anything written about bullets being smaller due to the lube layer? I have not. Have you discovered something no one knew about?

    I take no credit for the "discovery" as such. Perhaps I've just brought it to the forefront is all. In years past I've read several queries from those who have recovered cast bullets and found the diameter was less than the barrel groove diameter. There were many different suppositions as to why but the one that seem most logical was the bullet had to be riding on a layer of lube. The lube, not being compressed, added to the swaging effect on the bullets diameter on muzzle exit. Further testing of various cartridges at low medium and high velocities by myself,goodsteel and Lars45 have verified this.

    Just curious, can you measure the dia of the bullets in the nose section, as far forward as you can and just in front of first lube groove?

    The diameters of the noses are, where not obviously bulled by impact, is the same as the drive bands.

    PS did you have to remove those GCs from the bullets or did they separate after entering the bullet stop?

    No, I did not remove those 2 GCs. They were recovered in the test media about 1/3 to 1/2 the penetration distance.

    Sorry, last one. What dia are the GCs on the bullets?

    The diameter of the 2 GCs still on the bullets is the same as the drive bands. They are still tight with no indication of "springback".
    Larry Gibson

    “Deficient observation is merely a form of ignorance and responsible for the many morbid notions and foolish ideas prevailing.”
    ― Nikola Tesla

  10. #110
    Boolit Grand Master


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    Quote Originally Posted by Bigslug View Post
    More theory on gas check separation:

    Both copper and lead are getting squeezed equally by barrel and our mysterious "lube force", and there is the possibility of bullet bases getting melted under the gas check.

    Springback is going to be greater on copper than lead, and its affect is most likely to be seen at the front edge of the gas check. If its grip on the bullet has been compromised by compression and liquefaction at the rearmost corner, that front edge is our last remaining point of contact, and now it's gone.

    So on the one hand, I'm now thinking that annealing gas checks to render them as dead soft as possible may be a key part to this. On the other hand, I wonder if, due to the pressures and heat involved at these high speeds, if the gas checks are getting flash-annealed in the bore and this theory is much ado about nothing.
    That also, is what I am suspecting........
    Larry Gibson

    “Deficient observation is merely a form of ignorance and responsible for the many morbid notions and foolish ideas prevailing.”
    ― Nikola Tesla

  11. #111
    Boolit Grand Master Tripplebeards's Avatar
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    My avatar was 2100 fps out of my 1970 Marlin 336 chambered in 35 Rem. I shot a group at 200 yards right after the avatar group that measured 2 1/4”. Used smokes PC, a hornady GC, and sized about .0025” over. Alloy is 50/50 COWW and pure with 2% pewter added to total. The boolit is a group buy 200 grain HP. I also had a Ruger American 450 bushmaster I pushed all the way up to 460 S&W velocities but found out the best accuracy came around 2250 fps. It grouped 1 1/4” with 100% COWW alloy the was PCd,GCd, and sized a thousands over. I shot a 1 1/8th group with the same alloy and boolit set up but not water quenched. Boolit was a lee 300 grain FN. I do weigh my boolits and separate within 1 grain increments which imo everything helps when squeezing the tightest groups. They have been the only two rifles I’ve tried cast boolits in to date…so far.

  12. #112
    Boolit Master
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    Thanks Larry. Good info.

  13. #113
    Boolit Mold 450 Fuller's Avatar
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    "Gas check separation..." Even more critical in bottle-neck cases. BTW-If the GC falls off, separates and falls off
    into the powder column during the seating operation or before, you will encounter a serious/dangerous pressure excursion.
    A loose GC moving toward the neck in front of ignited powder IS NOT your friend. (Seen and witnessed.)
    For me and my house: straight wall cases IF a GC is used. The possible exception is the 30-40 Krag case.
    A very long neck that that would allow seating a GC d cast bullet to a chamber with a long leade/free bore. GCs are rattlesnakes sitting under a rock:
    they might stay and not bite...but.

    My use of cast boolits is somewhat limited to the following cartridges and rifles:
    Original 1885 Winchester HW Single Shot chambered in 45 2.1 inch; Sharps 1874 chambered in 45/2.1;
    Winchester pre-war Model 71 in 450 Alaskan; Model 71 Deluxe pre-war in 450 Fuller.


    " Only the dead have seen the end of war" Plato

    "Tolerance and apathy are the signs of a declining society" Aristotle

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  14. #114
    Boolit Master
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    YMMV. I've fired a few thousand rounds through my .308 now. All but a couple hundred have had gas checks seated below the neck and none have shed a check in the barrel. I've only recovered a couple hundred and all still had the GC's on them after penetrating around 12" through a dirt/sand backstop.

    I use only Hornady gas checks that crimp securely onto the base of the bullet. Most of the time I powder coat after applying the GC's.

  15. #115
    Boolit Master
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    So, after looking at this kind of thing for a while I decided to try a few things. First, in a discussion with Mr Gibson about ideal cast bullet barrels he brought up the slower powder again. I used to use Varget for cast loads but at lower levels, frankly where Varget does not do well (it likes high load densities). I've been using a lot of 4198 and 3031 instead and investigated higher velocity accuracy with those. I hit 'the limit' at around 2200fps. It occurred to me after all this that the faster powder was a contributor. I had some 4166 and it has done OK at sub-2000fps loads. Since it was slower I decided to ramp things up a bit.

    Rifle is a Savage Axis. Barrel is a .308Win from a Savage 12BVSS (26" stainless, 1:10 twist, fluted heavy varmint contour) and it has a bit over 4000 rounds through it so far, about 3000 of those have been cast. At sub-2000fps it is consistently under 1 1/2MOA. Most of the time (including this time) I am shooting the Accurate 31-210E bullet.
    They are nose and body sized, powder coated, then nose and body sized again (.302 nose, .310 body).
    They are sorted into 0.1gn batches. Hornady gas checks. Due to the throat they are seated fairly deep. The gas check is below the base of the neck.

    Click image for larger version. 

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    For this series I loaded up at my 'standard' 30gn of 4166 to give me right at 1970fps. This was my 'control' load. I then loaded up 36, 38 and 40gn. Keep in mind the max load for 4166 with a 210gn bullet is just over 40gn at just over 2400fps.

    So, on to the shooting. Early morning, temp in the 40-50F range. Wind was gusty at 5mph from left to right.
    I shot the control group at 200yd to foul the barrel and confirm the zero. I adjusted for wind and went to 500yd.

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    My main target was a 5" square gong. Yes, that is ~1MOA at 500yd. But, with a camera I can see the dirt kick up when I miss. I shot the rest and had some interesting results so I made up a video. I clipped out everything except the shots and only put in the 38 and 40gn series.

    Bottom line was, the 38gn load avg was 2340fps and had nice tight group. The 40gn load avg was 2455fps and definitely showed the effect of exceeding the RPM limit. Note that the extreme spread for the 40gn load was only 10fps!!! The es of the 38gn load was 40fps, and it still was pretty decent on target. The 40gn load was definitely max or over for this rifle with the cases having 'sticky' extraction.

    I think I can see a cone shaped 'wobble' from some of the bullets at the higher vel. I was kind surprised how close the first two came to the target.

    https://www.youtube.com/watch?v=cHZxFLsDLlE&t

    PS forgot. Of the two higher vel bullets that actually hit the target board, the holes were perfectly round. So the bullets did not hit grossly yawed or sideways.
    Last edited by charlie b; 11-12-2022 at 09:05 PM.

  16. #116
    Boolit Grand Master


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    Very interesting aand excellent examples. If you look at the video carefully you can see the helical arc of the bullets flight.
    Larry Gibson

    “Deficient observation is merely a form of ignorance and responsible for the many morbid notions and foolish ideas prevailing.”
    ― Nikola Tesla

  17. #117
    Boolit Master
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    Thanks Larry.

    The 'good news' is I am at least 300fps faster than I thought I could go with this setup and maintain decent accuracy. Being at jacketed velocity for this weight bullet is a bonus. Now I hope I can repeat it.

    I did pick up some N150 powder to try out. It is a little slower than 4166 so will see if I can eek out a little more velocity with it. Will also have to make up some XCB loads at same velocities and see what happens.

  18. #118
    Boolit Master
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    All good info!
    I love this thread!

  19. #119
    Boolit Grand Master popper's Avatar
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    two pieces of copper well enough and just laying one on the other will allow a weld to form over a period of time.
    NASA found a problem with connectors in space - they weld together!
    Getting old so I don't chase HV anymore. Results of my tests are - keep groove shallow - weakest point to twist. Bullet must be a high quality one. Alloy needs to be tough, I add a tad of Cu and NO tin. I did push a 145gr coated PB to 2050 fps (chronyd) from 1:10 18" McGowan barreled 300 BO AR, hot load of H110. Got near MOA @ 100 as sprue cut kept base from being completely flat. Had to really bang the plate to get the cut. IIRC had an almost 10 shot circle on the target.
    Whatever!

  20. #120
    Boolit Master
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    Thanks.

    It's called diffusion welding. The 'smoother' the surface the better the joint. The use I know of was in low temp physics work where any welding 'filler' was a contaminant.

    I am still surprised I got over 2300fps with some accuracy. If I can repeat it I will consider it a success.

    So, the other message might be that if 2350fps is 'ok' with a 1:10 twist, then a 1:12 twist might be good for 2800fps?

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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
PSP Pointed Soft Point Spz Spitzer Point SBT Spitzer Boat Tail
LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check