300 Blackout woes!

[Burnt Fingers]

I've got a 300 Blackout pistol with a 10.5" barrel 1:7 twist.

I've loaded up several different loads with the MP 311410 clone and none of them will group worth a damn.

I've powder coated and used Hi-Tek. I'm getting patterns at 25 yards that are more than 2' wide.

I had a red dot on it and thought there was a problem with it. I put a scope on and am having the same problems.

I'd try another boolit but there's aren't a lot of options available in a mid-weight bullet out there right now. NOE is sold out of everything.

With J-Word bullets it's inside an inch at the same range.

[Winger Ed.]

That's an awful fast twist for cast with much speed on them.
Ya might try playing around with the hardness and speed.

[BK7saum]

What load and velocity are your bullets? I shoot the 311410 subsonic in a bolt action and they are very accurate. You might need to slow them down. Is this the gas check version and what is your alloy?

[Dapaki]

130gr? You may have to drop it to sub velocity to play nice with that twist!

Whats your diameter?

[Ed_Shot]

Agree with Winger Ed...play with hardness and speed.

I have a 1-7 twist 300 BO AR and definately still learning. I use 3-2-95 alloy and find that water dropping in ice water makes a world of difference, harder is better. Also, I believe Larry Gibson when he talks about the "RPM Threshold." My 135 gr w/gc does great with RL-7 15.5~16.5 gr. but quickly goes to pot pushed faster. I do not have good luck with my 135 gr using H110/W296. My Lee 155 gr. shoots well with RL-7 16.5~17.5 gr. and is also accurate with W296 15.3 gr. Also having good luck with NOE 311299 over RL-7 16.0~16.5 gr. Take a look at on-line data from Sierra Bullets for 300 BO. Anyway thats my experience so far.

[Texas by God]

With so many rifles here that love cast bullets, I have given up on my 1-7" Blackout carbine. I have no use for subsonic and it shoots most any jacketed bullet well so it gets a pass. Based on my limited experience, I think the 10" twist 7.62x39 is a much better choice for a cast shooting AR15.

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[Burnt Fingers]

The J bullets I'm using are the Speer 125 TNT.

I've loaded the cast to where the pistol functions. No more. I don't have an idea of speed. No chrono.

I have the plain base version of the mold. The alloy for these was bhn 14-15.

[RU shooter]

With so many rifles here that love cast bullets, I have given up on my 1-7" Blackout carbine. I have no use for subsonic and it shoots most any jacketed bullet well so it gets a pass. Based on my limited experience, I think the 10" twist 7.62x39 is a much better choice for a cast shooting AR15.

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I agree if cast and normal speeds are what your gonna be shooting a 12 or 14 twist would be a lot better . A few years ago I did just that since I had no ambition for subs had a 20" 12 twist barrel with carbine length gas made up . Shot every kinda cast bullet I had well with a wide range of powders even got 4895 to work with 150-200 gr bullets

[BK7saum]

The J bullets I'm using are the Speer 125 TNT.

I've loaded the cast to where the pistol functions. No more. I don't have an idea of speed. No chrono.

I have the plain base version of the mold. The alloy for these was bhn 14-15.

I think the plain base boolits are your problem. Velocity has to be up there to get function and I just dont think the PB boolit can handle the pressure.

One check would be to download and shoot for groups. I know it wouldn't function but you would find the speed limit on the boolit

[Dapaki]

With so many rifles here that love cast bullets, I have given up on my 1-7" Blackout carbine. I have no use for subsonic and it shoots most any jacketed bullet well so it gets a pass. Based on my limited experience, I think the 10" twist 7.62x39 is a much better choice for a cast shooting AR15.

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I see great accuracy with my AR-15 in 7.62x39 as well. I can push them rather hard and they are very nice at 200 yards with PC boolits. Not seeing a lot of good results in 300 BO with PC boolits when driving them hard, they seem to be much more favorable at subsonic speeds with that fast twist.

This, by the way, is the very same issue I am having with my AR in .223 Wylde with a 1:8 twist. If I push the boolits hard enough to cycle the bolt, the accuracy drops off significantly.

[Fast Asleep]

I have built three Contender rifles in 300 BO, two with 10” twists and the third with a 7” twist. The two 10” twist barrels handle pretty much any cast bullet tried with good results. The 7” twist rifle only works when bullets are hard, heavy and slow—exactly what the original 300 Whisper was designed for. My next build in this caliber will be with a 12” or 14” twist barrel and expect it to be very accurate with bullets up to about 190 grains.

[skeet1]

Burnt Fingers,
I have a 16" AR with an 8" twist. I use the Lee / Ed Harris 312-155 bullet sized at .311" and while it is not a tack driver it does shoot reasonably well. Right now I am using Shooters World "Blackout" powder but have used 296/h110 and Lil'l Gun and they work well also. I know that this is comparing apples to oranges as I have a 16" barrel to your 10.5" but unless you have your heart set on shooting the mold you have you might like to try the Lee mold. The price is right and you can get a 6 cavity to keep your AR fed.

Ken

[popper]

260059
Bottom group. 1:8 BO pistol 145gr PB PC 50/50 alloy @ 50 yds. Bipod and rear sandbag. Vert. is probably the soft brace resting on bag. Figure ~ 1500 fps using A2400. Shot faster loads from it with no problems. Top group is 1:10 carbine pushed real hard (H110) with GC, bipod & bag. Pistol is harder to shoot from bench than in field. Slow and muzzle rise gets you, fast and recoil does the same. Standing your body compensates if you can hold on the target. Actually testing BLL at HV and getting low fps to cycle in pistol so not really shooting for accuracy.

[Lloyd Smale]

try the 130 rcbs spitzer gas check. I get great accuracy with it from 1700 to 2000 fps in my ars with 110, wc297 and wc820 (aa9) and it even shoots 1.5 at 50 yards out of my American with a pop gun load of 4.5 grains of unique. Powder coated in all examples.

[charlie b]

Twist rate vs velocity is an issue. Fast twist means slower bullet velocity is needed.

[Burnt Fingers]

I'll try loading down and see if I still get function.

I ordered a NOE 311-158-FN five cavity PB. Al doesn't have much in the way of .30 caliber molds right now.

[Ed_Shot]

I'll try loading down and see if I still get function.

I ordered a NOE 311-158-FN five cavity PB. Al doesn't have much in the way of .30 caliber molds right now.

I'd be real interested in hearing your review of that 311-158-FN. Thanks.