300 blackout

[Jason in TN]

Ok just bought a 300 AAC blackout with 500 primed cases and hornady dies have a crimp die on the way. Any one loading this up 1-10 twist 16in barrel. Bullets? Weight powder?
Any ideas where to start on a good accurate round. Does not have to be a subsonic round I will not be using a silencer.


Jason

[Dolomite_supafly]

Are you sure it is a 10 twist? It would be one of the rarer versions. Personally I like 10 twist over 8 twist but I would make 100% sure. I think 10 twist will be more accurate than 8 twist with most supersonic loads. I have two 8 twist guns and a 10 twist gun. Also, is it new? The reason I ask is most 10 twist guns were Whisper guns. The calibers should interchange but if you are loading ammo using dies for the 300 Blackout it can cause problems in some Whisper guns.

 

I know you said you have no plans to shoot subsonics but I will let you know this. I have found that the 10 twist will stabilize jacketed bullets up to 200 grains at velocities down to 1,000 fps. 8 twist will let you shoot jacketed 220 grain bullets at the same velocity. With cast bullet a 10 twist will handle 220 cast bullets and 8 with handle 250 grain cast bullets. Now some 10 twist barrels will be able to stabilize heavier but you must verify.

 

Also need to know the length of the gas system, carbine or pistol length. I suspect carbine length but it makes a difference on load data. With a pistol length gas system you can run a lot more different kinds of powders than with a carbine length.

 

For powders I would look at Lil'Gun, H4227 or H110. Those seem to make up the top 90% of powders used in the 300 Blackout.

 

Here is a great resource for load data, and not just for the 300 Blackout.

http://data.hodgdon.com/main_menu.asp

[Guest FIRSTLAST]

im using 17 grains of h110 and 150 grain sierra match boat tail boolits and am seeing good results. i dont have a chrono or i would give you some more info.

[Jason in TN]

Thanks it is a 1/10 twist carbine length any more info would be great will be picking up powder and bullets real soon. I now have dies separate crimp die 500 rounds of primed brass and a case gauge.




Here is what is on the barrel.

Jason

[Dolomite_supafly]

I have searched their sight and cannot find a 10 twist barrel in any length. I prefer 10 over any of the faster twists.

I will call them tomorrow to see if they have any in stock.

[MacGyver]

Here you go, Gordon:

 

http://shop.redxarms.com/75-STAINLESS-STEEL-300-AAC-BLACKOUT-PISTOL-BARREL-75300AAC.htm

 

It's a shorty, but it looks like they're rolling their own, so I'm guessing they could do about any length.

[Jason in TN]

Have loaded up some 150 grain hornady cycled find would not lock bolt back on last round most of the time.

Have also loaded some 135 grain Sierra hp will shoot them soon only loaded 5 of them for the first try.

May have to do some tuning to get every thing to work right.

Jason

[Dolomite_supafly]

Do not swap parts away from milspec on the lower. The upper should work with ANY lower that works with 5.56.
 
I would just keep increasing powder charges until it cycles or you see pressure signs on the primers. The powders I would try are Lil'Gun, H110, H4227 and A1680. If it will not cycle by the time you start seeing pressure signs then the port needs to be enlarged by a few thousandths. Continue the process until it locks back on an empty magazine. Make sure you are testing with at least two different brands of magazines.
 
With a carbine length gas system you are going to be chasing your tail trying to get 200 grain bullets to cycle at subsonics velocities. 200 grains is about as heavy as you want to go with a 10 twist at subsonic velocities. You can shoot heavier but I would not expect them to be stable 100% of the time. I definitely would never fire them out of a suppressor or muzzle brake. Carbine length gas systems tend to do really well with supersonics but not so well with subsonics unless there is a suppressor on the end of the barrel.
 

 

Here you go, Gordon:

http://shop.redxarms.com/75-STAINLESS-STEEL-300-AAC-BLACKOUT-PISTOL-BARREL-75300AAC.htm

It's a shorty, but it looks like they're rolling their own, so I'm guessing they could do about any length.

That is not going to work for me. My Form 1 says the barrel is going to be 9.5" and because it needs to be threaded for a suppressor I cannot just pin an extension in place. I guess I could give them a call and see how much it would cost.

 

Actually it is all dependent on whether the Lee 230 grain bullet will be stable in a 10 twist. It has turned out to be a great performer once it is powder coated. Also, because I am going to be hollow pointing the bullet mold so I may just keep things the way they are because 8 twist would be better than a 10 twist if shooting subsonic HP's. I still have a lot of decisions to make but I need to test everything before making a decision.

[Jason in TN]

Will likely not be shooting subsonic any way. Thanks for the info I am having fun playing with it.
Lots of Work right now will do some more testing beginning of the week. Thanks again.

Jason

[Jason in TN]

Ok update time.

Tried to increase the powder load until I got flat primers. Would cycle fine bolt would not lock back.

Next tried to take weights out of buffer still no go on bolt locking back. Still would cycle fine.

Put weights back I drilled the gas port out about 2 thousands and it works great now locks back on last round with both loads and grains of bullets. Will start working my loads back down and see how things work out and how well it will work with lighter loads.

Thanks for the info.

Jason Edited October 29, 2013 by Jason in TN