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9 inch vs 10.3 inch AR barrel

Posted: Sun Jul 10, 2011 12:14 pm
by tReznr
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?

Re: 9 inch vs 10.3 inch AR barrel

Posted: Sun Jul 10, 2011 12:18 pm
by 300Blk
10.3 has more velocity.
9 is more compact.

Re: 9 inch vs 10.3 inch AR barrel

Posted: Sun Jul 10, 2011 12:51 pm
by tReznr
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?

Re: 9 inch vs 10.3 inch AR barrel

Posted: Sun Jul 10, 2011 1:51 pm
by JasonAAC
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.

Re: 9 inch vs 10.3 inch AR barrel

Posted: Sun Jul 10, 2011 2:05 pm
by Tom12.7
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.
Tom

Re: 9 inch vs 10.3 inch AR barrel

Posted: Sun Jul 10, 2011 4:58 pm
by 300Blk
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.

Re: 9 inch vs 10.3 inch AR barrel

Posted: Sun Jul 10, 2011 7:39 pm
by tReznr
Thanks for the feedback guys. 9 inch barrel it is! :D

Re: 9 inch vs 10.3 inch AR barrel

Posted: Tue Jul 12, 2011 11:32 pm
by 82nd airborne
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.