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

Ian

Well-Known Member
Sometimes the internet is wonderful, sometimes near useless, it all depends on what you're looking for and what's already been done and posted. With regard to getting good accuracy with powder-coated cast rifle bullets at normal copper-jacketed speeds, the reports are fair to dismal and only a few people have really done any serious investigation. I want answers to the fundamental questions of accuracy potential, velocity potential, fouling issues, bullet designs that work best, alloys that work best, special loading considerations, and all that. Main reason for me is I want to abandon traditional lube and shoot my cast bullets through suppressors without leading. I've concluded there is no shooting HV cast bullets through a can without leading the baffles, no matter how good the load is, but powder coating eliminates the leading completely, so I'm looking to change all my cast rifle loads over to coated bullets and this is the beginning of that investigation.

First off, a brief test of my M1A, suppressed, fed from the magazine. I tried and tried to make the Lee C312-155 shoot in this rifle and it just refused to group. I tried different alloys, powders, loaded length, even single-loaded the cartridges and never found joy. The rifle will group fairly well with the NOE XCB bullet and even better with several others, getting into the 1 MOA at 100 category with the MP 30 Sil bullet and a lot of tricks, but the Lee bullet was a no-go. Until I tried powder-coating some.

Here's a photo of some of many targets "before powder coating:

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Here are the very first two groups I shot WITH powder coating...and bullets that measured 10.4 bhn (air-cooled 50-50) at 2,381 fps average velocity!

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Not match-winning at 1.75 MOA @100, but first try with no tweaking and butter-soft alloy didn't do too badly fed from the magazine. The main thing to notice is how dramatically the coating alone improved the accuracy of the load. Something to this I think.
 
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Ian

Well-Known Member
Some early work with my Mossberg MVP 5.56x45mm. I tried jacketed, then four different cast bullets without coating and had some very good results (posted in my MVP thread) using plain lead bullets at HV, but the muzzle brake leads like the dickens so I went back to the drawing board with coated cast. At first I was lubing them and trying different lubes, then I tried some without lube and got same to slightly better results...and NO high first shot flyer....by ditching the lube altogether. Some targets:

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Velocities of the MX3 powder-coated and without lube were running high 2500 to low 2800 fps depending on powder charge and seating depth and are 15 bhn water-quenched straight WW alloy.
 
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Ian

Well-Known Member
Please be patient. I'm posting from my computer and then editing photos on my phone and logging in to post them.

ETA, ok, done for now. I'm doing this in a mad rush before bed, been meaning to for weeks but haven't had time to drag out the targets. I have a stack of them and only posted a few, but they're typical and I didn't show just the best ones or fastest ones. Anyway, hope the jumble makes sense. What I'm learning with the 5.56 is that the barrel will probably need cleaning on principle after extended shooting, but even shooting in 105 degree temperatures, rapidly, with a suppressor, the PC didn't melt and ruin the bore. Oh sure I could make groups fade by getting the rifle barrel hot enough to sizzle spit and the ceramic coating on the can to smoke (talk about mirage!!! heat from the can is a real problem for precision shooting), but the coating didn't ever seem to completely fail like I feared it would. Lubed or unlubed PC bullets grouped about the same and heated the barrel about the same. Carbon fouling and some sort of buildup in the first two inches of the barrel, felt with a patch, finally made me brush and clean the barrel after about 350 rounds. Next group was a little "off", 2" at 100, but it got back to normal quickly. Normal, now that's the rub. Normal is 1.5 MOA for ten with 5-7 in 3/4 MOA, always flyers and no real pattern to them other than every 3-4, and they may be in the same direction or opposite, two together or spaced between shots in the core group. The alloy is way too soft for any of this, so that may be the problem. 1/4 of the bullet is in the powder space, which may be another. The nose of the MX3 lacks supporting surface area in the throat and at the base of the TC nose where it "rides" the bore...sort of.... so crooked starts are very likely with .008" total loaded neck clearance and so much to go wrong. Chronograph numbers don't correspond to flyers in any way I can tell. SD and ES could be better, but SD has been around 20-30 for most of these which is better than when I put lube in the grooves.

Right now I'm getting about the same results as the best of them at decent velocity, but I'm using far softer alloy than anyone else has been able to get away with. Dan of Mountain Molds has gone to 3100 fps and beyond with PC, lubed 7mm and not consistently gotten under 1 MOA at any speed with coated bullets...and he used 35 bhn heat-treated reclaimed shot for alloy, so I don't feel too bad so far about what I'm getting, especially since I have done exactly zero case prep other than size and expand the necks. Not even a case mouth debur on the 5.56 (started with new brass and kept using it, up to five reloadings on one batch of 100 now). The M1A is using WCC-08 that didn't even need the pockets swaged, I just trimmed, chamfered, and resized, and loaded them.

We'll see where I can take it from here.
 
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fiver

Well-Known Member
it looks like you just confirmed my friction testing...

IMO you can do a couple of things now for the next step.
modify the mold, change the pressure timing, or change the alloy.

your not really gonna be able to do much about the chamber or the brass fit.
[god I wish I could reference that thread I wrote up on Jay's site]
but fixing the first point of contact [is bigger better? or is a shape change needed] is unchangeable once it's done.
changing the throat timing event would be where I'd start looking.
if I seen an improvement there I'd follow it up, then I'd chase the alloy back around.
after that then go last resort and slightly modify the crush point to a stronger shape.
 

Ian

Well-Known Member
Ok, let's look at the throat timing event with the 5.56, more details:
  • No crimp, in fact some bellmouth is left. .0015-0018"" neck tension, any more and the 15 bhn bullets get squeezed.
  • Bullet is seated for a light jam, first point of contact is the nose base band with the land tops, some engraving due to band casting .222" instead of .218" per drawing, then it's coated. Third band and body is sized to scuff all the way into the parallel throat freebore. Bullet moves about half a band width forward before the band tapers and throat taper start to lay in with each other.
  • 3031 is just barely starting to burn efficiently at about 2650 fps, about 95% case fill. Might be a good opportunity for buffer but there's a lot of bullet sticking down in the powder space.
Maybe I'd better toughen up the bullets FIRST so I can play with neck tension, maybe a light crimp, or harder-hitting powders? I could go with a tick slower powder but I'm borderline as it is with consistent ignition and clean burn, and even the slower powders have a much faster pressure rise rate than 3031.
 
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Hawk

Well-Known Member
Well sorry to be slow on the uptake, but I'm not familiar with MX bullet that you're referring to. I tried searching the Forum, but it won't come up with anything. Can anyone post info on the 5.56 MX bullet you're referring to?
 

popper

Well-Known Member
I've used 335 & 4895 with good results, you need harder alloy even with the 1:11 twist. Your 31-165, 2700 in the 24" 1:10 LR308. Did find the gas port tends to cut a bit even with GC bases. You will probably get some PC and lead in the can, I do in the recessed crown and the flash hider on the carbine. I'm working on a RD style 170PB pushed hard (15-1600?) with relatively soft alloy in 10" BO pistol. Preliminary shows mostly horiz. spread which is ME. Over coating PC with BLL (stays sticky) keeps barrel cleaner but no other advantage I've found.
 

Ian

Well-Known Member
Over coating PC with BLL (stays sticky) keeps barrel cleaner but no other advantage I've found.
I wondered about that, it's still on my list of things to try if I start having bore conditioning or fouling problems. Filling the grooves, or even one groove, with various lubes only added the lube variable to the situation, didn't seem to improve anything other than keeping powder fouling soft and preventing any kind of PC residue from sticking. What I got in the first 2" of barrel after a few hundred rounds of no-lube may have been PC residue.
 

popper

Well-Known Member
Cleaned the rifle upper the other day, don't remember when last was (got to see if I can get some $$ for it), Eds Red without acetone. Couple dirty patches then clean. Never tried the PC/BLL in this one.
 

waco

Springfield, Oregon
Ian. I can't quite read the targets. What powder and how much are you using? I thought I saw 3031...
 

Ian

Well-Known Member
IMR 3031 for both rifles. 34 to 37 in the M1A loads and 20 to 22.8 in the 5.56 MVP, not all loads are posted but the groups for the 5.56 pretty much followed the same pattern as posted.
 

fiver

Well-Known Member
okay lets kind of clear this up.
you have the bullet touching metal, low neck tension, and there is some consistent horizontal stringing?

a buffer might help but I'd sweat it a bit with the bullet down in the case [chance of the buffer breaking down and sticking to the shoulder] the old puff-lon..... yeah a couple of grains of that could help.
 

Ian

Well-Known Member
It's more like tight clumps with flyers all around when I shoot ten at a time. The pattern doesn't change a whole lot within a 10K psi window, so that should eliminate a lot of things. The rest pretty much sums it up.
 
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fiver

Well-Known Member
got any 4895 or 4064.
it's just to look for a direction,,,, [if your seeing same ol same ol then you know]
you could speed the powder up a notch too and see if it gets worse or better.
then come back to the 3031.
it could simply be some riveting, or some unevenness entering the barrel.
a harder alloy could fix that of course but if a powder speed change fixes it that also opens up room for more velocity.

chuckle... same old story of chasing the speed wagon.
get stuck, look for clues, follow that trail, look for more clues.
 
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Ian

Well-Known Member
It gets easier every time, though, usually.

I've been afraid of getting poor combustion if I go slower and of spiking pressure too soon if I go faster. I have ten bullets left, maybe I'll try 4064 and see how it really does. Next step is make more bullets and wait for them to age out, and maybe also fool with another bullet design that I already have coated and ready to go.
 

fiver

Well-Known Member
it does get easier cause the signs are pretty much the same.

the only other thing is to use a double base easier to ignite powder.
the only one I can think of that's close is Accurate's 2200 but it's a ball powder.
[I'm still not sure where 2230 lands on the burn charts I have seen it listed as a near 3031 but use it more like a slow 4064 in most smaller cases]

you could use a filler to raise pressures, but those have their own problems and side effects.

oh.. are you weight sorting?
 

RBHarter

West Central AR
I know you don't want to hear this but ........ I had this old 06'........
Long story short it was really touchy about cases . The end results from both weigh lotted cases of one HS and water weighed cases was that every clump or in my case each group and flier was accounted for by case .
 
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