My 300 BLK rifle is a 16" right now. I typically only shoot it suppressed with subs, so that's a bit big overall with 8" can. Has a DD barrel right now and have had 0 luck getting good groups with it too. About 2.5" @ 100 yds is best I can get it with any load from a 110gr VMax to a 240 gr MBC. And I tried a ton of stuff in between. This is it's 2nd DD 16" barrel - I returned 1st one for same issue and kind of gave up on it after similar results with replacement.
Anyway.....the 300BLK has been shelved mostly & want to start getting back into it some more. I want to do an upper for my SBR using a 7.5" barrel which would give me about 15" overall with can. What I don't know is how well pistol gas works with suppressed 300BLK. My current is carbine gas and it runs everything well from supersonic to the slowest subs, suppressor on or off, it just runs anything & doesn't care. Standard carbine buffer, M16 bolt carrier, non-adjustable gas block. Would a 7.5" barrel swap & either straight or pigtail gas tube run as well under those same conditions?
Also, if anyone knows, I'm thinking I might have to increase the powder charge in my subsonic loads by a tenth or two to get the same velocity from the shorter barrel? Anyone have experience moving to a shorter barrel and needing to adjust the load to stay at the MV you want?
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