300 AAC Blackout

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Re: 300 AAC Blackout

Postby Thib » Thu Jan 16, 2014 8:14 pm

SirSqueeboo wrote:
newportri wrote:Shovel1966,
What is the barrel twist?

I might be going to TRGC myself this Saturday, so let me know if you are going so I can check out your 300 AAC ammo/gun :-)



The official recommended twist has gone from 1:8 to 1:7.


Looks like S&W split the difference @ 1:7.5
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Re: 300 AAC Blackout

Postby newportri » Thu Jan 16, 2014 9:06 pm

Seems like a pretty fast twist compared to other .30 caliber cartridges. Is that because with the same weight bullet the velocity is significantly slower than for example a .308 and you need (or can have) a faster twist?
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Re: 300 AAC Blackout

Postby SirSqueeboo » Thu Jan 16, 2014 10:56 pm

newportri wrote:Seems like a pretty fast twist compared to other .30 caliber cartridges. Is that because with the same weight bullet the velocity is significantly slower than for example a .308 and you need (or can have) a faster twist?


Yes. They found as companies were maxing out the weights of the subsonics that they weren't stabilizing well.
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Re: 300 AAC Blackout

Postby shovel1966 » Fri Jan 17, 2014 12:22 pm

I bought a CMMG flattop upper with a 16' length 1:7 twist. The groupings were pretty good with the 147gr bullets at about 1650fps and even better with the 180gr boattails traveling approx 1500fps. I had absolutely no cycling problems, but haven't shot anything close to subsonic yet. Another thing that may helped is I purchased the complete upper which was a dedicated 300 BLK and gas system is tuned to that cartridge instead of just changing out a barrel on an upper tuned to .556.
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Re: 300 AAC Blackout

Postby SirSqueeboo » Fri Jan 17, 2014 3:53 pm

shovel1966 wrote:I bought a CMMG flattop upper with a 16' length 1:7 twist. The groupings were pretty good with the 147gr bullets at about 1650fps and even better with the 180gr boattails traveling approx 1500fps. I had absolutely no cycling problems, but haven't shot anything close to subsonic yet. Another thing that may helped is I purchased the complete upper which was a dedicated 300 BLK and gas system is tuned to that cartridge instead of just changing out a barrel on an upper tuned to .556.


The barrel dictates the gas system, not the actual receiver.
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Re: 300 AAC Blackout

Postby newportri » Fri Jan 17, 2014 4:54 pm

....the right to keep and bear arms, shall not be infringed.
Check out our website here:
http://www.rifol.org/
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Re: 300 AAC Blackout

Postby shovel1966 » Sat Jan 18, 2014 7:29 pm

This is the actual upper I have. I believe it to be the same as the link above, but mine has a front sight on the gas block.

http://www.midwayusa.com/product/523619 ... lash-hider
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Re: 300 AAC Blackout

Postby SirSqueeboo » Sat Jan 18, 2014 9:34 pm

CMMG's melonite coating is supposed to be excellent, you did good. My go to AR has a CMMG barrel.
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Re: 300 AAC Blackout

Postby shovel1966 » Sun Jan 19, 2014 1:17 pm

I really don't know a lot about the manufacture process or quality of AR parts, but I am happy with the CMMG. I had looked at numerous complete 300 BLK uppers and this one happened to be in stock at Midway and on sale for $599.99.
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Re: 300 AAC Blackout

Postby SirSqueeboo » Tue Jan 21, 2014 2:24 am

Shovel, what groupings were you getting, and at what distance?

Thanks.
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