Results 11 to 14 of 14
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June 10th, 2020, 11:17 AM #11
Re: AR pistol converted to 300 Blackout - Won't cycle subsonic
I think it has a carbine buffer in it. Where did you get your lighter buffer & spring?There are two kinds of guns. Those I have acquired, and those I hope to.
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June 10th, 2020, 11:41 AM #12
Re: AR pistol converted to 300 Blackout - Won't cycle subsonic
OP, is your buffer spring also a carbine length spring? Also, take your buffer out and actually weigh it.
You said with a lightweight bolt in it it cycled fine with subs but still wouldn't lock open when empty. You could take some weight off the buffer. Either take your buffer apart and remove a weight or buy a lighter buffer to test that. It not locking when empty could be that the bolt is going back far enough pick up the next round but not far enough back to let the magazine follower to get into position to actuate the bolt release.
Buffers of different weights can be bought from just about anyone who sells AR parts.Ron USAF Ret E-8 FFL01/SOT3 NRA Benefactor Member
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June 11th, 2020, 09:42 AM #13Member
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Re: AR pistol converted to 300 Blackout - Won't cycle subsonic
First thing would be to be like xringshooter said, weight your buffer. that'll determine where you're starting and what modifications are needed. As others said, It sounds like your bolt isn't cycling fully back which is caused by the under gassing of subsonic rounds. Your choices are reducing the buffer weight, reducing the spring (reduced rate / yellow spring weight is about %20 less than standard), or increasing the gas pressure (but not really an option since you don't have an adjustable gas block).
Here's an article about buffers and springs and a reference chart with weights.
I got a JP Enterprises silent captured spring because I wanted to see if it really made that much of a difference in sound but honestly the jury is still out I'm not sure it's worth the extra cost.
Hope that helps,
Mitch
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December 30th, 2020, 11:34 PM #14Junior Member
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gilbertsville,
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Re: AR pistol converted to 300 Blackout - Won't cycle subsonic
Not to Captain Obvious, but I chased an "under gas" issue for an afternoon before realizing there was a carbine length gas system on this 10.5" 300blk! It was from a few years back when we were still experimenting. So I re-tapered the barrel, threaded and plugged original gas port, and drilled the new gas port to .087" to be able to install a pistol length system. As imagined it cycles everything fine now! ....Have fun, Gerry
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