Driving PC bullets at velocities over 2200 fps-Have you experienced leading or other?

[reedap1]

I am interested in anyone's experience in pushing PC bullets very fast, in this case, say over 2000-2200 fps and higher and if you have seen any deposition of material (lead or powder coat material) in the bore. I have been playing with a few calibers (375 H&H, 375 Winchester, 348 Winchester and most recently the 405 Winchester) with bullets on the lighter end of the scale for those calibers and driving them at higher velocity. To date I have not seen breakdown of the PC or any indication of leading.

I know a few members have commented about pushing their PC bullets to higher speeds and would be interested in feedback. I know accuracy is a different issue and often times lead bullets can be less accurate at higher speeds but do they foul the barrel? Theoretically I would guess there is a limit to the PC before breakdown, but my experiments to date have not show any issues up to almost 3000fps.

I would appreciate any insight from the members on their experiences. Thanks in advance,

Paul

[Bad Ass Wallace]

I have been experimenting with higher velocity PC's for over two years. I started with my 270 Savage pushing a 132gn cast to 2,260 with good accuracy.

https://i.imgur.com/CtMbKoRl.jpg

Worked up a load for the 7.62x39 pushing a 190gn cast boolit to 2,260fps, and a 55gn PC bullet in the 223 Rem to 2720fps.

https://i.imgur.com/Gc8Va4ul.jpg https://i.imgur.com/A5KkvJ4m.jpg

I have not tried any of these boolits on game but found that there is a limit where accuracy drops off. Searching the backdrop the boolits seem to "shatter" in the soil rather than deform.

[Hick]

I accidentally got more velocity than I wanted with plain based PC (2100 fps in an M1 Garand). 50 rounds fired, No barrel deposits and the PC did not come off the bullets (I recovered one and it was undamaged)

[barnetmill]

Does one need a hard alloy when driving a powder coated bullet to 2000 or more fps.

Could be an inexpensive way of shooting old military rifles, especially the 6.5 Carcano rifles. I would be interested in doing so for the 8x57 mauser guns.

[popper]

Need a tough alloy, not necessarily hard. PC will abrade a little, easy to clean, just like powder residue.

[charlie b]

Many of us have done it. The upper end of the vel limit is related to the rifling twist. For my 1/10 twist barrel above 2400fps and things get weird. No fouling issues, just too high a rotation rate.

This was posted in another thread but applies here as well. I do have to say the first three shots were half lucky :)

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

PS these are max loads for jacketed bullets.

[MaLar]

This is from my 35 Whelen 1x14 twist. Alloy 2 lbs Foundry and 12 lbs Lead. Hardness is about 12 plus.
Ranges is 100 yrds. No fouling clean bore when done.
308705

[mikeinnm]

A follow-up question to those who have done this: Are gas checks necessary? Is anyone seeing a limit to velocity without them?

[charlie b]

Yes. At least for me they are. I've tried plain base and they do not seem to hold up well over 1500fps. Also tried GC designs without checks and the start to 'fall apart' for me around 1200fps.

[405grain]

mikeinnm: The requirement for gas checks is more related to pressure than to velocity. That might be a little confusing because you need higher pressure to get higher velocities. There are several things that gas checks do, but the primary one is preventing high pressure gas from leaking passed the bullet as it goes down the barrel. These jets of high pressure/high temperature gas will vaporize lead from the sides of the bullet. When this lead vapor cools it will deposit inside the barrel and cause barrel leading. As a general rule, lower velocity loads like standard pistols, ie: 38 special, 44 special, 45 acp, 45 Colt, etc., don't require gas checks. Higher velocity (higher pressure) loads like rifle cartridges and magnum pistols can benefit from gas checks. For velocities much above 1400 to 1500 fps with any cartridge I'd recommend using gas checks. Without gas checks you might be able to get a little more velocity with powder coating than with conventional lubed cast bullets, but not much. Also, as a general rule, (though not always), bullets designed for gas checks are usually more accurate with the checks installed than without them.

Most reloaders are accustomed to jacketed bullet velocities, and see cast bullet velocities as a drawback. For people new to loading cast bullets there are things to consider. Jacketed bullets are encased in a copper shell that is many times harder than lead alloys. It takes considerably more energy (velocity) to cause this copper jack to upset and expand than it does for the lead core. Cast bullets don't have a hard metallic jacket, and expand properly at a lower velocity. In hunting applications other than varminting, really high velocity can make a cast bullet come apart too soon on impact with game, preventing good penetration. For a cast hunting bullet velocities around or below 2000 fps would probably work best.

For other applications like long range target shooting, a higher velocity bullet might be more appropriate. To get those higher cast bullet velocities with accuracy will require some more advanced casting techniques. Harder alloys, water quenching, visual inspection and weight sorting will be in the cards. Those higher velocities (above around 2000 fps) will require the use of gas checks. Personally I keep my cast rifle loads below 1900 fps, and am more concerned with trying to get good accuracy than I am with higher velocity. Don't make the mistake of judging cast bullet performance with jacketed bullets. They both work their best at different velocity regimes. Even at those velocities that cast bullets work good, using gas checks can be a big benefit.

[Rapier]

I drive the double coated 200 grain 358 RCBS plain base to 2,500 fps without any fouling in an AR. If done right you do not need any gas check at all.They shoot 3/10 inch at 100 with 1680.
You need to get a real hard alloy like 23 bh (70-20-10) to start with and forget the entire lubed bullet process. Shake and bake with a nose down bake.
This is the 358 MGP, on the left, a necked up, blown out 6.8 SPC with adjustable gas block, turned down to just function. It is a hog killing son of a gun.

The 35 Whelen would make 2,700 easy enough in a bolt gun, as would the 350 Rem Mag. More case capacity and slower powder, like 4350.

[popper]

2400 and above with PC, no leading,1:10 AR10 308W carbine. Yes, GC needed. 2000 from BO, still no problem, no GC. Need a tough alloy!!

[reedap1]

Thank you gentlemen for the information and experiences. It mirrors what I have seen in my limited testing ie. no shedding/depositing of the PC in the bore at high velocity (as confirmed by bore scope analysis) and no leading of course. Barrel clean-up is a breeze in most cases just a good liquid bore cleaner, but I will often use two treatments of Wipe Out and end up with a pristine bore.

I'm not trying to go for land speed records with my PC loads. Really my purpose was to develop lead/PC loads at higher velocities for practice and plinking to avoid having to continually adjust my rifle sights when switching back and forth between jacketed loads. I have found that the accuracy for the PC loads even at higher velocity is as we all know more dependent on bullet size and barrel fit. I generally size my PC loads 0.001" or so more than I would a conventional lead/lubed bullet finding in my experience that "fatter" PC bullets seem to shoot more accurately. I think the PC engraves the rifling very well. With many of the bullets I load, I can shoot them PC'ed and unsized with good accuracy thereby saving time in the production process.

I have not seen dramatic differences between gas-checked and non-gas-checked bullets but I am hesitant to draw any conclusion in that regard due to small sample sizes. I found the comment by Rapier to do a nose-down bake to be interesting and will give it a try.

I've been powder coating for about two years and am continually impressed at how well it works, For me, it has been a game changer, especially with my pistol loads. I am loading 38 Special PC light bullets for plinking made from free lead with Alliant America Select (very clean burning shotgun powder) for almost less than current prices for 22 rimfire (at least until my hoard of primers runs out and I'm forced to pay the new prices). I shot 875 rounds through a S&W model 66 and cleaned the barrel and cylinder with one pass of Hoppes #9.

Thanks again for the information,

Paul

[mikeinnm]

Thanks, everyone for the info. Lots of food for thought here, and it's amazing how much PC info everyone has.

Mike

[Mr Peabody]

A follow-up question to those who have done this: Are gas checks necessary? Is anyone seeing a limit to velocity without them?

I see problems at 1400fps in my .35 Whelen with plain base, gas checked I can go to 2250fps. Recoil in my Handi Rifle keeps me from more fps

[gloob]

Do high velocity rifle bullet ever leave fouling like pistols and big bore, slow rifles do? The main problem I ever hear about is poor accuracy, tumbling, and lead buildup on muzzle attachments.

I have had all of these issues when trying to push cast 223 hard enough to cycle my rifle. But still no bore fouling (but I use gas checks).

Maybe at some point there's enough gas following the bullet out that it blows out the fouling while it's still molten?

[reedap1]

gloob,

Are you referring to problems with conventional lubricated bullets or powder-coated ones? If the latter, in my experience I have never seen any hint whatsoever of leading with a powder-coated bullet. I've pushed rifle bullets to 2600 fps and pistol bullets to 1400 fps and do not see anything other than powder fouling. Finding bullets in the range berm from those loads has shown that the powder coating remains intact unless it hits rock etc. Others will have more experience than me but I suspect you can nearly load PC bullets up to jacketed bullet levels and never see lead fouling...accuracy might not be there but I am now at the point with all my PC bullets I forget about any leading issues and focus purely on accuracy at any velocity.

One last thought I have taken a powder-coated bullet (Ford Light Blue) and heated it with a propane torch to the point where the lead melts and bursts the "PC jacket" but the PC never burns or melts until I hold the torch on it for a good long time.

It has been a real game changer for me. Good luck

Paul

[gloob]

I meant either, really.
When I pushed my non-PC GC rifle bullets too hard, they painted the flash hider silver and the bullets exploded midair or hit somewhere outside the scope of a barn door. But there's no lead in the bore. I've never seen fouling in any of my rifle barrels, and I have shot cast bullets in all of them (with gas checks).

Seems that PC might be equally effective for fouling. Accuracy appears to be the first thing that goes, same as with nekked gc'd bullets. I wonder if it's because of bullet deformation/melting inside the PC jacket, or just because of the problems that a thick coating have on accuracy/symmetry.

[charlie b]

First, I don't have muzzle devices on my rifles. The velocity limit of PC bullets is the same cause as conventional lubed bullets. It is not due to leading but due to the spin rate of the bullet. If the rifling twist is slower you can push the bullets faster. How fast? Depends on several things but mainly the quality of the cast and the design/dia of the bullet.

How accurate can you be? Look up results of competition at the Cast Bullet Association.

[gloob]

So if you use a low enough twist rate, you can shoot cast bullets as fast and accurately as jacketed, even up to ridiculous speeds?

The lower the twist rate, the shorter your bullet has to be, I suppose. That would obviously limit long range ballistics and accuracy. But shortie cast bullets at 4000 fps? Coming out whole and stable?

We have rifles with low twist rates, and they're generally big bore and SLOW, in the realm of mid 2000 fps and less. Kinda sorta to make the power with mass over speed, limited by the bullet tech at the time. If PC breaks that limit, we should be able to make wildcat rifle calibers that shoot cast bullets at 4000 fps.

https://www.fieldandstream.com/story/guns/the-fastest-rifle-cartridges/
220 Swift:
"The Swift required Winchester to design bullets that would stand up to extreme speed. (I’ve seen Swifts liquefy lead cores; the targets were sprayed with it. I’ve also seen bullets literally vaporize a few yards from the muzzle.)"

The way my flash hider was painted in silver in one shot, it makes me think part of the bullet was coming out completely melted. I suppose it might have been lots of little tiny bits, but it sure looked like a spray of molten lead. I also can't imagine how the bullet would fragment into such tiny pieces just a half inch away from the muzzle, before it would even have time to orient end-over-end.

Copper is ductile and has a high enough melting temp, and those are two good reasons to use it for bullet jackets. But it is also a dense metal with good thermal conductivity. Nearly the best thermal conductivity of any reasonably common element. Same reason it works for cooking, it would carry heat away from hot spots on the surface of the bullet (such as might occur from gas exploding through a small channel between bullet and bore) and redistribute it all around, rather quickly, so as to heat up the entire bullet (or entire base of the bullet in the case of a gas check) rather than allowing one spot to melt way earlier.

Interesting we also use aluminum for checks, now, and aluminum also has a very high thermal conductivity. When there's any gas blowby between the bullet and the bore, the gas will be hottest at the base and cooler at the nose, as heat is transferred from gas to the bullet. Thus that part of the base where the leak is occurring, is going to be the first part to melt, if you believe in the theory or myth or BS that gas blowby melts bullets. And putting a thermal conductor over the base might help keep that spot from melting just long enough while the bullet makes it out the bore.

But of course this wouldn't prevent a gas check from also "gripping the rifling," if that's your cup of tea. I'm not sure what good that does, though, if the check is free to spin round and round the base of the bullet with relatively little friction/fit to stop it.

PC doesn't have the structure to "grip the rifling" does it? But it works a lot like checks, in practice. Allowing higher velocities/pressures with cast bullets. It's not a good thermal conductor, nor does it have much mass. But it does act as a thermal insulator.

Any material with more springback than the lead alloy of the bullet would also maybe help to stop leaks from occurring in the first place. I think this might be another reason gas checks and/or PC work. But again, PC coating is very thin. At any rate, when gas checks or PC fail, accuracy tends to go off first, before fouling occurs. I believe it's because the bullet has started to melt. The PC/check gets the entire bullet out without leaving fouling. But the bullet won't be accurate, because it won't be stable when part of it is gone or melted and misshapen.

If the thermal conductivity of copper/aluminum provides some of the benefit of a gas check, it should be better to install your checks before powder coating.

[gloob]

I took a look at some charts on metals, for thermal conductivity and density.

Pure copper is the best, about twice as good as the second best (non exotic/precious) metal, which is aluminum. It is also over 3x as dense, so that would make it potentially 6x better for the same thickness of check/jacket.

But I don't think gas checks are pure copper? Not sure what alloy is used in gas checks, but the thermal conductivity can go way down for alloys. Eg. brass is 70% copper and 30% zinc, and it has only half the thermal conductivity as aluminum (but since it is 3.5x as dense, it's still nearly twice as conductive for a similar thickness of check). You want to burn your fingers, put a piece of brass against a disc sander with your bare hands.

Zinc washers have also been used as "gas checks." This is the reason I looked up these charts. I already knew copper and aluminum as the two metals used in heat sinks. Surprise surprise. Zinc is also a very good thermal conductor, a bit better even than brass and nearly as dense.

This thermal conductivity factor may have been overlooked, to date, by us reloaders. This might be part of the reason gas checks are generally thicker as the caliber increases. A 223 check doesn't have very far to spread the heat to.

Lead has a very low thermal conductivity down there with steel. I.e., where the lead bullet is getting heated, you can more easily melt the surface off while the core is still cold. This is one of the reasons it is so easy to weld steel. Aluminum has a way lower melting point, but it's more difficult to weld, partly because it's harder to control the spot that melts, even after preheating the entire piece to avoid that initial heat sinking/spreading.

Soda can checks might work fine to reduce/eliminate fouling. But I wonder if they retain accuracy when pushed hard enough, compared to thicker checks. Beside being really thin, they also have a thin plastic coating on the inside and some sort of coating or at least paint on the outside. I suppose that wouldn't be too different from the oxide layer that will be on normal checks. But I would suspect soda can checks might work a little better if you make them inside out, though a bit less colorful.

Defense industry, are you seeing this? To improve tank armor against shaped charges, maybe we ought to be laminating the steel armor with layers of high temperature thermal conductors. (Probably already doing that.)

Mythical silver bullets: silver has a fantastic thermal conductivity, almost as good as pure copper and even more dense. It might make a good material for a jacket or a gas check. Gold is nearly as good, its way denser than even lead, and the melting temp approaches steel. Might make for a good jacket or even solid super high velocity bullet. Should be relatively affordable if the price of primers keeps going up. :)

I'm not sure why this post would make anyone angry, but I'm sure it will.

If you are shooting normal cast velocities, using the right speed of powder, the correct alloy and quench and PC/GC, no your bullet won't melt. But the max velocity and pressures of your higher velocity rifle cartridges will be much lower than for jacketed, per the reloading manuals. There seems to be a cap on pressure and velocity, for all practical purposes, just looking at Lyman cast data.

When my bullets were spraying out the muzzle, I am pretty sure it was because my bullets were too soft, because I was using a powder and charge that was commonly recommended. Most everyone suggests to water drop, in order to get cast 223 up to at least 20 BHN. I used a mix of 1/3 lino, but I didn't do the water quench. I managed to get my rifle to shoot and cycle, with a lesser load, but that clogged up my gas port with lead. I have read that cast bullets clogging a gas port is a complete myth, just like melting of bullets.