I'm done...

[Burnt Fingers]

I've been trying to get cast boolits to shoot in my 300 Blackout AR Pistol for a few months now.

Nothing seems to work. I really wanted the MP 311410 boolit to work. If I can keep five rounds on a paper plate at 20 yards it's a miracle.

The NOE 311-158 FN is SLIGHTY better.

NOE 311-198 SP doesn't group either.

MP 311-235 is my last hope.

With the other four bullets, HP and solid on the 311410, I've tried a total of 72 loads. Several different powders.

The barrel is a 8.5" 1:7 twist. It will shoot j-word 125 gr bullets and 147 gr bullets into small holes.

Cast....forget about it.

It it too much to ask to have a semi-accurate cast load that functions in an AR-15?

[Winger Ed.]

1 in 7 seems like an awful fast of a twist for cast.
I ain't no expert, or even close to one, but I'd think you'd have a leading problem with it too.

[JMax]

I know with my Norwegian Krag in 6.5x55 (twist 1/7.5”) that most suggested loads were too hot until I throttled the velocity back to 1350ft/sec under the 140000 RPM limit. The question is what MV were you getting?

[rtyler8140]

1:7 is going to be the hurdle. Lower velocity will be more accurate, but may not cycle. My 300 AR is 1:10 and I'm seeing promising things from the Lee 150 & 170 with H110. I am running into similar issues with my 5.56 1:7. I found that if I push them too fast, I can't hit paper @ 50 yards. I have been able to get a 1.5" group @ 50 yards, but because im downloading the powder so much, it's pretty dirty.

[shortlegs]

The lee 155 for 7.62x39 works great in my ruger bolt gun and should work in your ar. I use h110 and lil gun, avg 2 in groups at 100 yds. 300 yrd gong is no problem. All my loads are super sonic. Alloy is WW and air cooled boolits

[PowPow]

OP: What's the hardness of your alloy? Lube(s)? Any leading? COL?

[charlie b]

Fast twist, short barrel. If you want this to cycle the action I suspect you are going to need a heavy bullet (230gn) probably around 1000fps.

If you use light bullets and try to drive fast enough to cycle the bolt, they will be spinning too fast for decent accuracy. Probably get leading as well.

If you insist on lighter bullets, I'd suggest powder coating as you might be able to get higher velocities without leading.

[Lloyd Smale]

ive got 2 ar15 300 pistols and one 16 inch rifle and all three of them shoot the rcbs 130 spitzer gas check real well. 2 inch or better groups at a 100 yards out of the rifle and the pistols with redots will do the same at 50. I cast them out of about 18bhn gas check them and pc coat them. That is with very little load development. Does it with 110 4227 and wc820. Couldn't get the 155 lee to run reliably out of my 16 so I never bothered any further with it.

[Burnt Fingers]

The alloy is half lino half pure.

All boolits have been either PC or Hi-Tek.

I haven't tried any gas checks as the molds are all plain base.

I've been looking for a slower twist barrel. The slowest I can find is a 1:8.5

There is no visible leading in the barrel...but the muzzle device has lead deposits and the tail of the bolt does too.

[gpidaho]

Burnt Fingers: A different barrel than yours but my 16" 1 in 8 300 Blackout AR really shoots well using the Noe 129gr.SP over 17gr. LilGun. These are gas checked and powder coated. Gp

[Green Frog]

When I built my 300 BO (Carbine length) I needed an adjustable gas valve on the barrel to get reliable functioning at subsonic speeds with light bullets. Have you considered changing your gas block and cranking it down almost all the way so you can back off on velocity? Lead deposits anywhere in the system are not desirable nor do they add to accuracy nor functionality.

I’m pretty much of a novice with the Blackout guns, but that’s how I would attack your problem (before investing in a new barrel with only slightly slower twist!)

Froggie

[Burnt Fingers]

I've been thinking about an adjustable gas block.

[lar45]

Lloyd, what kind of velocities are you pushing in the rifle and pistols?

[MrHarmless]

I also have a barrel at that twist rate. I highly recommend a heavy bullet, like 230 grain.

The Lee 309 230 5R works reasonably well for me. ~1.5 inches at 50 yards over a charge of H110.

[Larry Gibson]

Short barrel with a fast twist made for heavy bullets just subsonic.

With the 311410 PB PC'd cast bullet you, no doubt, are pushing them way too fast just to get reliable functioning and hence, no accuracy.

I suggest a heavier GC'd bullet in the 200 +/- gr weight range and keep them under 1300 fps. I'm not a fan of PC or HT coating but some seem to make it work. I prefer traditional lube.

[BK7saum]

What are your velocities? Since your molds are plain base, you probably wont be able to exceed 1500-1800 fps and still get accuracy. wrong mold for the problem. I'd bet a gas check mold would work much better. If you want some of the gas check MP311410 bullets holler at me. I dont have your alloy available though. I could cast some of straight wheelweights and water drop them if that would work. I like the 311410, but I shoot it hollowpointed and subsonic in a couple of bolt guns.

[Texas by God]

I got tired of spinning my wheels on my 1-7”.300 BO 16” carbine with cast. I simply wanted a flat nose boolit to go around 1800 FPS for hunting. I never got acceptable accuracy even sized at .311”. To make it worse, I built a 7.62x39 AR that shot the same boolit faster with great accuracy on the first try..... (1-10” twist). I’ll just use 110 and 125 j-words in the little Blackout and be happy from now on. I have zero interest in subsonic loads.

[Burnt Fingers]

I've got the MP 235 gr mold and boolits from it. I was going to load them up last week but my little buddy ended up at the vet Tuesday and I was taking care of him all week.

It's hard to give a bird meds...really hard.

He's doing a lot better now.

I'm going to load the heavies up and see if they work for me.

I have a carbine length 7.62x39 upper. I'll have to scrounge up some brass and give those lighter boolits a try in that. If it works I might get a pistol upper in that cartridge. I've got a spare lower or two laying around waiting for a project.

[dangitgriff]

I've been trying to get cast boolits to shoot in my 300 Blackout AR Pistol for a few months now.

Nothing seems to work. I really wanted the MP 311410 boolit to work. If I can keep five rounds on a paper plate at 20 yards it's a miracle.

The NOE 311-158 FN is SLIGHTY better.

NOE 311-198 SP doesn't group either.

MP 311-235 is my last hope.

With the other four bullets, HP and solid on the 311410, I've tried a total of 72 loads. Several different powders.

The barrel is a 8.5" 1:7 twist. It will shoot j-word 125 gr bullets and 147 gr bullets into small holes.

Cast....forget about it.

It it too much to ask to have a semi-accurate cast load that functions in an AR-15?

Try the 350 Legend instead. Easy conversion.

[Lloyd Smale]

load does between 1750 in my 7 inch gun to 2000 in the 16

Lloyd, what kind of velocities are you pushing in the rifle and pistols?