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Thread: Accuracy at higher velocities and PC method

  1. #1
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    Accuracy at higher velocities and PC method

    Have any other members spent any time conducting accuracy tests at higher velocities (2500+) using different PC methods as the input variable?

    I've been tinkering w/ 3k+ loads...playing around with different PC application (static gun, shake n bake, dip and cook, etc) as well as different cook methods (stood up and laying flat mostly) to see what, if any, impact they have on high velocity loads.

    Interestingly enuf (purely anecdotal at this point) bullets that were cured lying flat seem to be more consistent than bullets that were cured standing. Application method hasn't appeared to be a big factor that I can tell (haven't tried acetone or solvents yet)

    Educated guess:

    * Standing the bullets slumps the paint toward the base and creates a bullet profile that increases the taper from tip to base (ever so slightly), taking the bullet out of its designed profile.

    * Laying them flat allows the paint to flow over the bullets more or less with the same thickness across its entire surface. Eg- no top-to-bottom taper increase.

    I've not noticed anything like this in my 9mm loads. They've always grouped the same no matter what I do, but 1k fps is a far cry from 3k fps.

    Thoughts?
    Last edited by 36Power; 07-27-2020 at 01:52 PM.

  2. #2
    Boolit Master
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    What size bullets? Accuracy in my .308 starts to go bad just over 2000fps (1:10 twist barrel). Smaller diameters should do ok at a bit higher velocities.

    Yes, I stand them up to bake. FWIW I have measured diameters and the only increase in dia is if there is build up at the base or just in front of a driving band. Sizing removes any build up at the base. There is a variation in PC thickness from bullet to bullet. When using 'shake and bake' that variation is minimized if you 'tap' the excess powder off. To prevent base build up I 'wipe' the base of the bullet before standing it on the baking sheet.

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    Tiny mothers.....223. My curiosity has to do with different coat/cure methods having different performance as velocity increases.

    EG: Is anyone else noticing that as velocities increase different PC methods seem to perform differently? Never noticed such a thing when doing my 9mm. With these 223s, it seems like the heavier the coat of PC and the more sizing required, the wilder the grouping gets...Two batches, both dip and cooked. One cured standing, one lying flat. Neither produced great groups, but the standing ones were worse noticeably worse...Trying to figure out why that might be. Paint slumping was my best guess, but who knows tbh.

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    Quick question...when you wipe the base of your bullets, do you remove all of the PC? IOW- the bottoms of your bullets are not coated, they are bare lead?

  5. #5
    Boolit Grand Master popper's Avatar
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    i don't do 223 but you are adding weight to the already light boolit. If the PC has anomalies in thickness, you unbalance them. I tried wiping the PC off the base (308W) and found little difference. Again, for 223 there probably will be a difference, TL PC will be uneven on the base. I push to 2700 in 308W with the rifle upper, still accurate but your fast twist 223 will get the rpms up and any unbalance will definitely cause a problem. Standing up to cook they tend to get fins on the base (of PC) so try running the base across sand paper to remove them.
    Whatever!

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    36Power good to see people experimenting with PC.

    More information please:
    Platform used (AR, Mini14,----)?
    barrel twist rate?
    GC or no GC?
    powder coating used?
    Bake time and temperature for powder coating cure?
    smokeless powder and charge used.?
    Did you tap off all excess PC or not?
    Have you tried any spraying yet?

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    Quote Originally Posted by popper View Post
    i don't do 223 but you are adding weight to the already light boolit. If the PC has anomalies in thickness, you unbalance them. I tried wiping the PC off the base (308W) and found little difference. Again, for 223 there probably will be a difference, TL PC will be uneven on the base. I push to 2700 in 308W with the rifle upper, still accurate but your fast twist 223 will get the rpms up and any unbalance will definitely cause a problem. Standing up to cook they tend to get fins on the base (of PC) so try running the base across sand paper to remove them.
    TL PC? What is that?

    And yeah, these little bullets are a BUGGER. Hyper sensitive to the smallest variations...Interesting observation: My bullets cured standing have this slumping toward the base AND this very slight ripple effect in the surface running along the length of the bullet. Think in terms of the PC flowing down the bullet in very fine 'streams'...as opposed to the PC flowing around the bullet's circumference as it lies flat. Make sense? You can feel the ripple if you lightly touch the surface of the PC while rotating the bullet, but you cannot see it with the naked eye. This doesn't happen on those that are cured flat.

    No idea if this stuff matters. Just hunting for reasons I'd see such variations in grouping when everything else is basically the same. Hoping some of you guys might have tinkered with curing methods and found any differences as velocities increased.

  8. #8
    Boolit Master
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    I wipe the bases of my .30 cal bullets to prevent the 'finning'. What little is left is taken care of when sizing.

    I have tried without wiping and noticed not much difference when using gas checks. The sizing process takes off the extra and the tough gas check is not distorted in the process. The powder left on the base of the bullet has no impact on the bullet. Yes, you can sand them and the gas checks won't suffer much. I just think sizing is easier.

    Plain base bullets, if I do not wipe, do have a 'fin' on the base that has to be taken off somehow. When sized it distorts the lead base and creates problems. I tried sanding and it just means the base is distorted as well unless you are VERY careful and can sand a perfectly square base. I just find that wiping them before baking takes care of the problem and leaves me with more accurate plain base bullets.

    The ripple may be because your PC coat is too heavy. Do you tap the bullets to shake off the excess?

    PS what powder and temp are you using?

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    Quote Originally Posted by Conditor22 View Post
    36Power good to see people experimenting with PC.

    More information please:
    Platform used (AR, Mini14,----)?
    barrel twist rate?
    GC or no GC?
    powder coating used?
    Bake time and temperature for powder coating cure?
    smokeless powder and charge used.?
    Did you tap off all excess PC or not?
    Have you tried any spraying yet?
    Basic 5.56 load I've been working on...I've chatted about it in the plating thread. Same super hard alloy.

    This is an AR. 1/9 twist, 20" barrel. Good gun, always been accurate. I have a Ranch Mini but haven't ran them thru it yet.

    23.8 gr VV N133 or 24.1 gr VV N530
    No GC...we're going commando here
    Custom spitzer mold, NLG.

    PC is a dual cure rate poly clear coat. Can cure at 400 at 12-15 mins or 350 at 20 mins. I do a cold oven start so I ramp the heat up to 400, then start the timer.

    Coat is super thin (needs to be in this case). I drop the bullets into the PC, pull them out, tap them off, and either stand or lie them flat.

    I have a HF ES gun...used it many times on my 9's. Everything works with the 9s tbh. Haven't used it on these cuz that thing throws such a heavy coat.

  10. #10
    Boolit Grand Master popper's Avatar
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    You might try a different powder. I tried smokes black and it rippled too - due to faster 'cure' time. His red flows very well, no ripples. TL is shake & bake. PC has a flow/liquid temp range where it melts/flows but doesn't cure. Higher temp then cures it. Your hard alloy is now AC hardness, need to W.D. after baking. And wait a week before shooting.
    Whatever!

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    PC is a dual cure rate poly clear coat. -- what brand and color are you using?

    You don't mention what part of the US/world you are in

    1 in 9 is a really fast twist

    what are you sizing to?

    super hard alloy.--- 20 bhn? 30 bhn?

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    I do water drop after PC. I use the copper sulfate method you first talked about here. It's primarily Lino/WW with Cu...Not terribly worried about losing hardness. This is tough stuff.

    I have some HF red, I'll give it a shot. That stuff's always coated well, too well for this application tbh.

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    Quote Originally Posted by Conditor22 View Post
    PC is a dual cure rate poly clear coat. -- what brand and color are you using?

    You don't mention what part of the US/world you are in

    1 in 9 is a really fast twist

    what are you sizing to?

    super hard alloy.--- 20 bhn? 30 bhn?
    Pac NW...Great climate, not humid at all. (but to all of you lurkers from California it SUCKS here...you'll hate it. Rains all the time. People are ********. Don't come here anymore...seriously, just don't )

    Alloy deets are above. Bullets go into PC somewhere near 30. Can't speak to after PC but I water drop them again.

    Prismatic Paints clear coat, I size to .224 before and after the PC.

    Re twist rate- I'm pushing it for sure. Mostly why I'm being so anal about all of this little stuff. I may find different result from the Mini. Ya know, I have a carbine upper for the AR. I could try that, but it's 1/9 also.
    Last edited by Minerat; 08-01-2020 at 12:32 PM. Reason: language

  14. #14
    Boolit Grand Master popper's Avatar
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    I sprayed with HF red 308 and it worked fine.
    Whatever!

  15. #15
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    Here is a question for you guys. How can one tell what the base line accuracy is? I would think that there comes a speed where you would achieve poor accuracy from your cast bullets if they were Powder Coated or just using a very good lube such as some of the ones from white label/lars. So when or how can you know if it's too fast for PC or just too fast for cast.

  16. #16
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    Nothing is really too fast for PC. The coating protects the bullet and bore.

    Conventional lube and gas checked bullets can also be fired at quite high velocities, if the lube is good enough. Not all lubes are created equal.

    For the proper lube/PC bullet the velocity limit is based on the spin rate of the bullet. The faster it spins the more problems you will get. Two theories, 1) at higher spin rate minor flaws cause the bullets to spiral or 2) at the higher spin rate the tensile strength of the lead allows deforming of the bullet in flight. The spin rate is dependent on diameter of the bullet, ie, the larger the dia the lower the critical spin rate. Either way at some velocity you begin to lose accuracy.

    To get a baseline you need to start at lower speeds and work up. My most accurate loads in the .308 are in the 1700-2000fps range, depending on the bullet (both weight and shape). Barrel is a 1:10 twist.

  17. #17
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    Thanks Charlie,

    Exactly what I was thinking, but a further question for you and/or the group.

    Just because we can push a cast bullet fast using PC, doesn't mean that it's going to be accurate. It just means that it didn't lead the barrel or disintegrate after leaving the barrel. I have been casting for 5 or so years. Advice in this craft has gotten so good, that I never have leaded a barrel. We have lubes, bullets, and documented instructions that would make it hard for someone to lead a barrel.

    But for the AR... I see lots of posts saying "I get 2.7k fps (or insert other number) with my AR cast loads" but at what accuracy? Does PCing AR loads at high velocities lead to better accuracy?

    Personally I would take 2moa at 100yards any day for a cast AR load with speeds above 2.5k. But how does a person know it's the PC that was the key allowing for accuracy at higher velocities? I suspect if there is a general rule here but as of yet unknown.

    We have the guidelines/rules that you laid out, very concise and proficiently I must add, I have a hard time eloquently explaining that to friends of mine. I personally believe that both rules apply.

    Quote Originally Posted by charlie b View Post
    1) at higher spin rate minor flaws cause the bullets to spiral or 2) at the higher spin rate the tensile strength of the lead allows deforming of the bullet in flight. The spin rate is dependent on diameter of the bullet, ie, the larger the dia the lower the critical spin rate.
    So when one introduces PC to the mix, do either of those rules above change? Or is a PC bullet that is accurate at 2,500fps a bullet that would have been accurate at 2,500fps with the right traditional lube? That's the question I can't seem to figure out. And I'm talking as a general rule, not case by case basis depending on the barrel stats.

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    ^^^^ Great post.

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    Quote Originally Posted by Dimner View Post
    So when one introduces PC to the mix, do either of those rules above change? Or is a PC bullet that is accurate at 2,500fps a bullet that would have been accurate at 2,500fps with the right traditional lube? That's the question I can't seem to figure out. And I'm talking as a general rule, not case by case basis depending on the barrel stats.
    Can't say for sure...but educated guessing suggests: 1) No, but it could make it worse. 2) Maybe...if PC can prevent or mitigate said deformation.

    My observations after reading about everybody's efforts w/ ARs here and including them w/ my own: Lotsa guys have gotten to 2500+ in their ARs using lube/GC/PC or some combination thereof. I have to believe, that a bullet that can be made accurate with a GC and lube, can be likewise accurate with a GC and PC.

    Can't say how many have been able to get 2" groups at those speeds, but of those who have, you can bet the farm it's been done with both PC and lube.

    The real zeitgeist on Cast Boolits is finding a way to get 3k and be accurate w/ the tools we have available right now. Not impossible, but so difficult.

  20. #20
    Boolit Master
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    YW.

    Please do state what caliber and twist when asking or describing how fast a cast bullet is fired. It is extremely difficult to have an accurate cast bullet much above 2000fps with a .308 and 10 twist. With a 14 twist, then 2700fps is probably doable. I do not know what the rpm limit is for a .223.

    You can use a 12 twist .223 barrel and shoot a much higher velocity accurately than you can with a 7 twist.

    If you really want higher velocities, go find a slower twist barrel, or have one made. If you do, understand that you may not be able to shoot reduced loads in it due to bullet aerodynamic stability issues.

    PC may or may not increase the limiting velocity of the cast bullets. I suspect it does add strength to the bullet itself but cannot prove it. I suspect the thickness of the coating makes a difference. But, does it put off the balance of the bullet if applied unevenly? And how uneven can it be before there is an issue? Don't know that either.

    Lot of things to explore with cast bullets in rifles.

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BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
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