My quest for speed and accuracy with powder-coated cast bullets

[Ian]

So you're pushing the Accurate 31-165C to near jacketed speeds in an AR-10? Are you powder coating them? The groove above the gas check and the single, small groove make a huge difference vs. a true slick.

I've had 5.56 drop primers in the barrel extension when the throat was too tight, never had it happen on a Blackout.

 

[popper]

Yes, 2400 fps with the optical chrony, PCd. That is the one I shot MOA @ 200. I overcoated some with BLL and wanted to see fps difference but - well - shucks. The blade gave me numbers from 1300 to 3300- got to work on that thing more - worked fine on the 30/30. This primer got stuck in the bolt cam slot! Had to hammer it out with screw driver. Got to be more careful when priming cases for the AR15s. Don't think the LR primers would fit in the handle groove.

 

[Ian]

Well, there ya go. MOA with cast at 2400 in a bottom-feeding semi-auto. I was getting ~1.5 MOA or better at 200 with mine, going a little faster. Nothing to it.

 

[Ian]

Back at it again today with the heavy-barrel Savage. What prompted this was me finding about 25 Lee 312-155s left over from a powder-coat/heat treat test. These were 390⁰ for 30 minutes before the quench and only got to about 15 bhn (ww plus a pinch of tin) and were sort of set aside as a failure. Anyway they got sent to the 100-yard butte at just under 2600 fps to see what would happen. First eight were spent getting on target and beating up my 75 yard gong, then these three at 100. I took the photo when going downrange to re-pin the target due to backblast through the hole shot in the front cover of the trap tearing the paper loose. Hat to repin twice more before it was over:



Beauty, right? Well this powder coat thing can be a little strange. I had a lot of suppressor mirage but still should easily have been able to shoot an inch group so that's not an excuse for this:



That's 11 shots and only one more went into the hole with first three.

Shot the last one into my oiled sawdust trap and noticed some base porosity. Thin sprue plates tend to cause that and 50K psi will dang sure show you the error of your ways:

 

[fiver]

that's why I spend the 20-30 minutes with the scale.
tedious and boring for sure, but it can save 'some' head scratching.

 

[Ian]

I may have to start.

Typically I don't choose a Lee mould for precision HV shooting, and better moulds plus good casting technique have mostly eliminated bullet quality as a variable for my casual (i.e. no money lost on that occasional flyer) pursuits in the past. But now I'm taking 1800 fps alloy to 24-2600 with 15 kpsi more pressure than usual and some ugly is starting to show up.

 

[Spindrift]

Interesting to see that bullet base. Very instructive. I must admit that bullets with a little porosity in the base have passed my visual sorting regimen, if everything else is OK.

That first 3-shot group surely was impressive. But I think the 11- shot group is also very good. 11 shots with medium- hardness alloy, warp speed, approx. 1,5 inch group..... A very good group, and also a good illustration why we don’t judge accuracy by 3-shot groups
If this is how your rejects shoot, I’m not sure you have to have to modify your bullet sorting process

 

[popper]

The cupping of the GC is pretty normal but some think that a GC will solve the base pin-hole problem. Nope. I find the same on PB PCd, small centered divit is OK but poor ones get recycled. A reminder of the copper crush method of pressure testing!
Often think of getting a nose pour mould for HV shooting.

 

[Ian]

Definitely why three shots is a pretty worthless test.

Another thing going on here is the annealed check (as a side-effect of curing the paint with the check installed), though like Popper says at HV even an un-annealed check will cave in if there is a bubble, void, or foamy spot in the bullet base. Little puckers in the center of the base from casting hot and cutting the sprue early are a sort of trademark of my casting and a way to determine consistency of timing. Emphasis on the 'little', as sometimes those tearouts can be pretty big and I cull those along with anything that isn't perfectly on-center. The bullet in the photo above obviously has a soft spot not where the sprue was. The other bullet I shot into the trap yesterday and posted in Spindrift's MP 311-180 thread (an extra that somehow didn't get shot last range outing) does not have any problems with base porosity and has been shooting very well for me. Again, a thicker sprue plate allowing me to "wash out" the sprue from each cavity with a stream of excess alloy while the pour cools and then leave a tall well of metal makes for pretty solid bases.

Popper, yeah, I got a Hoch 310-160 nose-pour mould that I'm seriously considering trying to use if I can fabri-cobble some handles to fit. Veral hates them with a passion because the base plate tends to stay too cold but I think maybe I can figure a way to make it work.

 

[Ian]

One more general comment here. At this point I've got the speed part of PC rifle bullets licked with usable accuracy. Pretty happy with the hunting load I have tuned up for the LR-308, especially since the rifle has a flexible, polymer receiver and is a "field rifle" where 1.5 MOA to 200 yards is more than adequate and the velocity of the load is enough to maintain good trajectory and 2000 FPS+ impact velocity out that far. Now I'm wanting to focus more on the accuracy part, maybe not at 90% of maximum cartridge pressure

So much to learn now about how alloy, jump, fit etc. affect accuracy, and jumping off into full pressure loads has turned into a re-visit of every part of the loading process.

 

[freebullet]

Sometimes a lot of testing is required to get back to square one. later you'll make correlations that we all learn from. Trigger press time is well spent either way.

 

[Reloader762]

Things I've learned about powder-coated, gas-checked rifle bullets so far:

1. The bullets don't need lube up to and beyond equivalent jacketed bullet speeds.
2. Full-power, full-pressure loads can be used in ordinary, production-quality barrels without leading.
3. Light carbon-fouling akin to shooting jacketed bullets is all I get at high-velocity, one wet and two dry patches gets it all out (five rifles tested so far, repeatedly).
4. The first shot from a CLEAN barrel goes in the group, usually in the center. Very predictable.
5. Powder coating allows full-power rifle loads with reasonable hunting accuracy in ordinary hunting rigs using bullets of HALF the BHN normally required, making for more effective expansion at extended ranges. This, of course, extends the minimum hunting range if you don't want excessive meat damage.
6. Powder-coating drastically reduces the lead fouling of muzzle brakes and suppressors and virtually eliminates leading of both piston and DI gas systems.
7. The coating hasn't proven any gilt-edged, match-winning accuracy yet, but then again I haven't (nor am I inclined to) pursue it to that level given the velocity and alloy concessions that will likely be necessary. This quest was for usable hunting accuracy with appropriate alloys and particularly for semi-automatic rifles which we don't see at many cast bullet shooting matches.
8. And for the biggie.....After all this testing at both extremely low and high velocity, I consider the Quest for Extreme Bullet Lube 100% fulfilled. Our dear departed friend Felix Robbins was right all along when he kept indicating that some sort of polymer was the solution to the bullet lubrication challenge. Who knew all those years ago that it would take the form of a TGIC-crosslinked coating?

Oh, and I guess that means this quest, for speed and accuracy with powder-coated bullets, is fulfilled as well. Happy shooting!

With the exception in point #6 regarding muzzle brakes and suppressors neither of which I have on any of my rifles, I can personally attest to your findings being spot on with my limited HV powder coated cast bullets as well. My newly acquired budget Rem. 30-06 got me started pushing the envelope with cast lead at higher velocity using the same Lee 170 gr. FN bullet I was already shooing at factory velocity in my Sav. 30-30. I'm pretty confident I can push the 170 gr. Lee, powder coated, gas check bullet past the 2300 fps. range I'm at now with 3.5 grs. of usable charge weight left before I hit Max. load but I'm getting MOA accuracy and for around here with the limited shooting ranges that's plenty good at where I stand now.

My Sav. 99 in 300 Sav., M44 an M91/30 in 54r followed by my three SKS rifles will be my next HV cast lead projects. They all are cruising along at a comfortable clip in the 1700 to 1800+ fps. range at the moment using 170 gr. bullets in the 300 Sav. and 185 an 215 gr. bullets in the 54r's and 155 to 160 gr. in the SKS rifles but I'm going to see how far I can push them as well an still maintain accuracy, but I like my upper mid-range loads as well so they will always be on the to load list.

Your post #253 was spot on as well, I personally have nothing agents them but I never buy grooveless bullet molds for handguns or rifles, something just always told me to buy the ones with grooves and it's proven to be a good choice, plus I can always revert back to using my RCBS Lube A Matic for lubing bullets if needed if PC is not an option as I have all my fallback loads using all the bullets I shoot using traditional lube.

I apply my gas check after the bullets are coated, standing all my bullets on the base to be cured and I cull any bullets with bad dimples that I plan on checking before they ever make it to the coating process, the few that have dimples left by the sprue plate go into the plinking bullet pile, they still get coated and are just shot with no gas check as low-velocity loads. I will gas check a few bullets and coat them and see how they turn out if the coating on the base of the check is not even I will just use my Dremel tool mounted on my bench and a fine wire brush and clean it off.

Fouling with PC'ed bullets has never been an issue, it was hardly even one with traditionally lubed bullets either, regardless of how few or many rds. I shoot the bores are always nice and shiny when I'm done shooting and as you said one wet patch and a couple of dry patches are all that is needed for cleanup, traditional lube did leave the gun a bit more dirty overall but the bore was fine.

It's funny that you mention bullet dia. In general, I usually size my 30 cal. bullets to .311" and with all the rifle I usually shoot those dia. bullets in they shoot great but with the 06 a .311" dia. bullet was a bit snug to chamber so I size them to .309.5" which is what my sizer actually sizes them to and it shoots just as accurately with an identical load and the bullet chambers much more easily with no fuss.

on The Basement Articles #5: Alloy for accuracy and hunting I pretty much switched to 50/50 about a year ago for all my shooting needs, I air cool for pistol HP bullet and water quench for the HV loads. The HV 30-06 load is cast from 50/50, PC'ed and water quenched right out of the toaster oven after curing then checked and sized and allow to sit for a few weeks to age harden. If that alloy and powder coat can hold up to that it want be a problem with anything else I'm shooting.

 

[popper]

If I use the 24" barrel on the LR-308 I get 2700 fps with accuracy. Same load, just more barrel.
I did 2100 fps chronied and MOA @ 100 with 145gr PB in BO carbine ONCE. I carefully cast and cut the sprue to get a clean sharp cut - no divit at all. It should have been better but IMHO I can't make the base totally flat - cutting makes the plate rise just a bit - not measurable but there. Cut the sprue with gloved hand and just feel a 'pop' when cut. Target showed mostly a circle of holes, 18" 1:10 barrel. IIRC 10 shot string. GC mould is easier!

 

[Ian]

Popper, I cut the sprues two seconds earlier than that. If you feel resistance and then it giving way there will be a bump. Also press down on the sprue plate tab as you open to help flatten the bullet bases.

762, I very much appreciate the peer review and for sharing and comparing, only a few people are pushing the envelope with this stuff (or if they are they aren't celebrating much on the internet) and sometimes I feel like a voice in the wilderness. I want a little more out if the process than Elvis Ammo or Ed Harris are getting, it seems like most people automatically think "cast bullets = light loads and practice ammo" and don't even try to maximize the benefits a coating process can offer, much less apply some real thought to the whole thing beyond just getting powder on the bullets and baking them. Please keep sharing your results and anything you have learned about loading techniques unique to the "painted jacket", this is fascinating stuff.

 

[Ian]

I tried something a little different in an effort to get this Mossberg 5.56 to shoot, but once again no dice.

This was the Lyman 225415, gas checked and powder coated, sized to scuff the freebore, seated with just the gas check in the case mouth and front band (which had been taper-bumped) snuggled up in the ball seat. 12 grains of RX-7 being close to Lyman's "accuracy load", it seemed a good place to start.

At least it prints right where the 68.4 grain bullets doing a full 1000 FPS faster do. Sigghhhhhh....



The only consolation is it won't do much better with jax. I did clean the rifle before shioting these because the last loads it had through it were lead-free bismuth/tin/antimony lubed with LBT Soft Blue. The barrel has always been hard to oush a patch through, especially when cold after using LBT, but I was surprised at how smoothly the patches went through it this time. At one time I had used Iosso bore paste the polish the bore and that helped, but the lead-free bullets seemed to have smoothed it up a little more. Could be my imagination though, it's been a while since I cleaned it. In any event, I noticed that the patches are tight from the chamber end until they reach the barrel flutes, then they get considerably loose all the way to the other end of the flutes about an inch before the muzzle. That finding has convinced me to try one more Hail Mary pass before junking this barrel: Going after it with a full set of Tubbs lapping bullets. I'd kind of been saving those for my AR-15 with the super-lumpy barrel and pinned muzzle brake, but I can buy more if they work on this Mossberg. Then I can set the barrel back about 8-10 threads and rechamber with a .223 Match reamer.