9 inch vs 10.3 inch AR barrel

Discussion about rifles in 300 AAC BLACKOUT (7.62x35mm), hosted by the creator of the cartridge.

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tReznr
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9 inch vs 10.3 inch AR barrel

Post by tReznr » Sun Jul 10, 2011 12:14 pm

I'm getting ready to build an AR pistol upper in 300 blackout with a barrel from Delta Company Arms. I'm primarily interested in shooting suppressed subsonic, but will likely end up loading up a few supersonic rounds to play with down the road.

Is there any substantial reason to go with either 9 or 10.3 inch barrel length? Or is that 1.3 inch difference of barrel not nearly enough to matter either way?
"Our Country won't go on forever, if we stay soft as we are now. There won't be any America because some foreign soldiery will invade us and take our women and breed a hardier race!"

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Re: 9 inch vs 10.3 inch AR barrel

Post by 300Blk » Sun Jul 10, 2011 12:18 pm

10.3 has more velocity.
9 is more compact.

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tReznr
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Re: 9 inch vs 10.3 inch AR barrel

Post by tReznr » Sun Jul 10, 2011 12:51 pm

I understand that typically speaking a longer barrel length = higher velocity, but what does the 10.3 inch barrel gain over a 9 inch barrel? 50 FPS? 100 FPS?

Also, when shooting full power/supersonic ammo through a 9 inch barrel with a suppressor attached is baffle erosion a concern with this cartridge like shorty 5.56 barrels? What about with a 10.3 inch barrel?
"Our Country won't go on forever, if we stay soft as we are now. There won't be any America because some foreign soldiery will invade us and take our women and breed a hardier race!"

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Re: 9 inch vs 10.3 inch AR barrel

Post by JasonAAC » Sun Jul 10, 2011 1:51 pm

tReznr wrote:Also, when shooting full power/supersonic ammo through a 9 inch barrel with a suppressor attached is baffle erosion a concern with this cartridge like shorty 5.56 barrels? What about with a 10.3 inch barrel?
No, not at all like the 5.56.
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Re: 9 inch vs 10.3 inch AR barrel

Post by Tom12.7 » Sun Jul 10, 2011 2:05 pm

I bet that in most applications, you would hardly notice 1.3" of difference in performance. Unless you plan to run an unusual forend that won't work with a 9" barrel. I'd say go with the short one, since you plan to primarily run it subsonic silenced anyway. I don't think you could reasonably tell the erosion difference between the 2. Sure, the longer would erode a can less, but by how much? I'd say little.
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Re: 9 inch vs 10.3 inch AR barrel

Post by 300Blk » Sun Jul 10, 2011 4:58 pm

tReznr wrote:I understand that typically speaking a longer barrel length = higher velocity, but what does the 10.3 inch barrel gain over a 9 inch barrel? 50 FPS? 100 FPS?
About 8 fps for subsonic and 45 fps for supersonic. It is small, and that is why we make 9 inch barrels and not 10 inch barrels.

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Re: 9 inch vs 10.3 inch AR barrel

Post by tReznr » Sun Jul 10, 2011 7:39 pm

Thanks for the feedback guys. 9 inch barrel it is! :D
"Our Country won't go on forever, if we stay soft as we are now. There won't be any America because some foreign soldiery will invade us and take our women and breed a hardier race!"

-Lt. Gen. Lewis B. "Chesty" Puller, USMC

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Re: 9 inch vs 10.3 inch AR barrel

Post by 82nd airborne » Tue Jul 12, 2011 11:32 pm

The only reason we even make both is that slot of people like handguard/can combos that won't quite work with the9". Performance is negligible between the two as Robert said.
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