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Posted: 8/19/2026 2:56:55 PM EDT
[Last Edit: Kalashnikov762][Edited]
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Although a decades long gun nut, im just getting into the 300 Blackout caliber. I'm looking for an upper for a pistol brace lower. I want to use Berrys 180 SP and H110 or Lil Gun. Is 7.5 inches of barrel long enough to burn up a subsonic load? Will 6 inches work the action and burn the powder and not soot my suppressor quickly? Im figuring 1 in 8 twist should stabilize 180's. If I cant get the action to cycle with 180's, will a 1 in 8 stabilize a 200gr Berrys SP? Subs will be the diet of this upper.....maybe exclusively. What say the hive? |
| I have three .300 BO, all built on different uppers. A Maxim Defense 508 8”, a DDM4 PDW 7”, and finally a Gemtech (S&W Axe) 8” upper. I usually run 200 GR subs, but have run a couple of supers through them. All have run reliably suppressed and unsuppressed. The DD is gassy AF and I like shooting it least of all, although I like the short length and weight. The Maxim and Gemtech are closely tied for performance, although the Maxim is a little heavier, and I don’t like that the handguard extends slightly past the muzzle, which limits certain suppressors. I like the Gemtech, which was rebranded as the S&W axe. YMMV. |
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I still think 9" is the sweet spot for 300BLK. I've tried going shorter but ended up going back to a 9" Originally Posted By ROCK6: I think if you're exclusively running subs, it doesn't matter and you can go shorter if that's a preference. |
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