300 BLK Not Cycling Subs Reliably

Derek8404

Derek8404

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As the title states, looking for suggestions on what to try. I’m shooting AAC 220gr with a 10.5in barrel using a superlative arms adjustable gas block. Suppressor is a Reaonator K.

I’ve played with the gas block and have it tuned in to where it will cycle most of the time, just won’t lock back after last round and one click either direction makes it either not eject or won’t feed the next round.

I am going to try it on a different lower as this one has a LAW folder on it and I’m not sure if that extra weight from the BCG extension could be the problem. Any ideas?
 
Get Off My Lawn said:
I have a LAW folder on my 10” 300BLK. It wouldn’t lock back, even with the gas block fully open. I checked port alignment, then opened up the gas port to the next numerical drill size and it runs 208g subs and supers reliably.
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I’ll give it a shot on a different lower then.
 
Still worth trying on a different lower first. The LAW adds some extra weight to the BCG. What brand upper and barrel?
 
Average Joe said:
Still worth trying on a different lower first. The LAW adds some extra weight to the BCG. What brand upper and barrel?
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That’s what I’m thinking too. Built the upper, think it started life as a PSA, then I added a BA barrel, superlative arms gas black and Geissele handguard.
 
Derek8404 said:
That’s what I’m thinking too. Built the upper, think it started life as a PSA, then I added a BA barrel, superlative arms gas black and Geissele handguard.
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I’ve never had or heard of any issues with BA’s gas ports, but anything is possible. I’d check gas block alignment and different lower. If neither of those work, then like @Get Off My Lawn suggested. Open the gas port to the next size up.
 
Average Joe said:
I’ve never had or heard of any issues with BA’s gas ports, but anything is possible. I’d check gas block alignment and different lower. If neither of those work, then like @Get Off My Lawn suggested. Open the gas port to the next size up.
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I’d be surprised if BA’s gas port was missized. I had a very hard time finding 300BLK build data when I made mine. I had the barrel custom made.
 
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Derek8404 said:
I’ve played with the gas block and have it tuned in to where it will cycle most of the time, just won’t lock back after last round and one click either direction makes it either not eject or won’t feed the next round.
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Perhaps I’ve misunderstood, but I have a question. If you turn your SA block to full gas (that’s 18 clicks or 4.5 turns out) does it run correctly?
 
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Wish I got to this post earlier, sometimes, opening up the gas port is not the final solution.

I have a 8" 300 blk barrel from BA. Kept the regular a2 front sight/gas block unmodified. I use an H2 buffer and https://nemoarms.com/product/300-blackout-custom-carbine-buffer-spring/
No issues with locking back on subs or cycling at all. Try this spring and see if it resolves your issues. 9/10 it does.
 
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Bocephus said:
When my 300BLK had trouble with subs after I switched to a 6.5” barrel and SA AGB, I had to play with the buffer weight and spring to get it to run without issue (to echo @ThatDudeVinny )
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Yeah, usually buffer weight and spring is the best solution. Especially when you want to manage over gassing. If you have a proper weight and spring, you can get a rifle to cycle properly (especially on subs) without opening the ports all the way. Ideally, you'd run a proper buffer/spring setup, and have subs lock back consistently, 95% of the time. That way, when you run supers, it doesnt gas the crap out of you.
 
ThatDudeVinny said:
Yeah, usually buffer weight and spring is the best solution. Especially when you want to manage over gassing. If you have a proper weight and spring, you can get a rifle to cycle properly (especially on subs) without opening the ports all the way. Ideally, you'd run a proper buffer/spring setup, and have subs lock back consistently, 95% of the time. That way, when you run supers, it doesnt gas the crap out of you.
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You didn’t run into any issues with the bolt unlocking early?
 
What weight buffer are you running? I have a suppressed 10.5" 300 blk, and I have no issues running 220gr subs on h2 buffer and full gas.
 
Sly88 said:
What weight buffer are you running? I have a suppressed 10.5" 300 blk, and I have no issues running 220gr subs on h2 buffer and full gas.
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Standard weight.
 
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