Ways to consistently increase pressure for gallery loads

Ian

Notorious member
or to exceed the leads ability to grip the rifling at the start of the journey.

Or near the end of the journey. This is what I see building up in the blast chamber, brakes, and on baffles when running cans with HV, uncoated cast. This is kind of like the relax point with some lubes you see when the lube doesn't thin out enough near the end of the barrel and the lube dumps out as the pressure falls off...except it's with alloy washing out instead of lube. Drive side abrasion makes gas leaks and lead dust blows out ahead of the bullet. Lots of stuff we don't see happening until there's a spot to catch what's coming out of the muzzle. I think it's fixable by tuning alloy, lube, and pressure curve, but I also think that at a certain point when pushing things up a paradox of alloy strength and lube viscosity creeps in where you just can't go any faster without some washout. Powder coat fixes that issue so easily I haven't bothered to really work out the details with regular lubed cast .22s.
 

BHuij

Active Member
I’ll watch for signs that my bullet is disintegrating on my next set of tests.

But there are a lot of ways to explain what caused this buildup. This is the first time I’ve ever removed the flash hider, so anything I’ve ever shot might be contributing to the buildup. My first couple hundred test rounds were air cooled COWW, so way too soft. I also had a set of around test rounds that used Felix lube instead of PC somewhere along the line.

I’m trying to stick to one thing at a time though. Next step is to replace the FH with a thread protector and see what that does to groups. Hopefully I’ll see them shrink a bit without the FH screwing things up at the muzzle.
 

fiver

Well-Known Member
definitely down at the end can be an issue.
if it's damaged at the start it certainly isn't gonna fix itself, and if the pressure does bleed off like well in a hole in the barrel that can cause an issue also.
the bullet is actually relying on pressure to keep it puffed up against the barrel and suddenly that base support is gone..
this happens in all guns regardless.
someone out there has some kind of math law that says something like pressure drops by half every the distance is halved.
so at 3"s it's 40-k at 6 it's 20 at 9 it's 10 [maybe it's 12 it's 10 it's early] etc. or something like that.
 

popper

Well-Known Member
I have no idea why maufacurer's put flash hiders on ARs - not like they do any good for us. Yes I understand the old law. You got leading there. You can even tell where the grooves are. I'd carefully use the vinegar/wash solution to remove it. Hardware stores have cheap plastic (red so you may be mistaken for shooting an airsoft gun) protectors, else take the upper to a LGS, they typically have 15$ ones. Or just black elec. tape.
 

BHuij

Active Member
So although I have swapped my barrel on this AR to .300 BLK, I just can't seem to leave well enough alone with this "cast .223 in an AR" project. Despite results that are frustrating at times, it's been such a good source of learning, and something in my nature makes me want to attack this challenge until I've tackled it. I just ordered a stripped upper so I can put my .223 barrel on it and switch back and forth between the two cartridges on my lower.

I still will be playing with cast .223 in my bolt gun, but I'm going to keep this project going on a slow burn as well. I think the first step here is to get jacketed ammo shooting well through this barrel before I play anymore with cast though.

I have a theory on why accuracy didn't improve very much when I ditched the flash hider for a thread protector. If you look at the pictures on page 6 of this thread, all the buildup and junk on the crown of my barrel is not making for a favorable muzzle exit situation for any projectile. I don't think I'm going to do any better than 3-4 MOA with anything until I have a cleaned up crown. How would you go about removing that fouling? It's deceptively hard. I'm really wary about messing up my crown, so the only thing I've really tried is scraping at it with brass tools, which didn't really accomplish anything.
 

fiver

Well-Known Member
you'll just have to soak it and scrub it.
once you get that done inspect it real well for burrs and the like.
JW started a thread some time back about re-doing some crowns and how easy they were to re-cut.
 

BHuij

Active Member
I have some ammonia-based bore gel, Hoppes #9, and CLP. Guessing none of those are going to be the ticket?
 

Ian

Notorious member
They do make a 20" HBAR and its even cheaper. The ss barrel can be worked on or lapped if necessary and doesn't have all the little thimble-thin cutouts that make the inside like a snake full of eggs. I'd avoid the cheap mellonited barrels because they're hard as coffin nails and the one I got has a throat so tight it blows the primers right out of 5.56 ball ammo. Can't throat melonite with a reamer.
 

BHuij

Active Member
Yeah, I'm not ready to give up on this barrel. Near as I can tell the barrel should be fine, it's just the crown that DEFINITELY needs some work right now.
 

BHuij

Active Member
I just picked up another stripped upper so I can have swappable completed uppers for .300 BLK and .223. I still need to get somewhere with a bench and vise so I can torque the barrel nut up to spec and install the forward assist, but it's all together for now.

I also got some Slip 2000 Carbon Killer delivered. So far I've done two 15-minute soaks of the crown followed by scrubbing with a brass brush. The crown appears undamaged by this treatment, but the lead on the crown is definitely starting to come off. I had to go to work, but I think with a little more elbow grease tonight, my crown should be in like-new condition. Later this week some 55gr FMJs should arrive. I think I bought 250 of them, hopefully that's enough to establish the actual accuracy potential of this barrel. If it turns out I got a stinker, I'll probably just get a new barrel for .223 sometime in the future. Maybe go with an 18" and a midlength gas system instead of carbine.