A heavier buffer weight to cure short-cycling? Advice, please.

January 18, 2026, 04:54 PM

quote:
Originally posted by sigfreund:

Without an adjustable gas block, what do we want? Something that functions okay with a wimpy toy load to make the suppressor owners grin, but then causes excessive bolt carrier speed with a round that is intended for serious purposes?

This is why my range toy is a suppressed AR 9mm. I personally have no interest in throwing $2 300blk subs for giggle factor when I can throw $.25 subsonic 9mm. Supersonic 300blk doesn't really interest me either when I can use a 5.56 loaded with the Barnes 70gr TSX or something similar. Or step to a 6 ARC or 6.8 SPC if I am looking for a cartridge with more oomph out of a small frame AR.

January 18, 2026, 04:56 PM

IndianaBoy

quote:
Originally posted by sigfreund:
The idea of a heavier buffer made no sense to me, but I didn't want to answer my own question.

That was probably advice given by someone who either didn't listen closely enough to understand the exact nature of the problem or by someone who doesn't actually understand how an AR functions but has heard of the heavy buffer solution for other AR related problems.

January 18, 2026, 05:01 PM

IndianaBoy

quote:
Originally posted by sigfreund:
I can’t provide a lot of details about this question (it’s not my gun), so I’m looking for the best guess/advice I can get. A short (~11") barrel AR type rifle chambered for 300 Blackout that I do not believe has an adjustable gas block does not cycle properly with some loads.

The gun fires and ejects the fired case properly, but the bolt does not cycle far enough to pick up and chamber a round from the magazine. The problem occurs with what I believe is a PSD 220 grain FMJ subsonic load, but not with Hornady Black 110 grain V-MAX ammunition that functions fine. The advice given about the problem was to install a heavier buffer (exact type I don’t know), and that was tried without curing the problem with the PSD ammunition.

I don’t have a lot of experience with the 300 BLK cartridge or with the type of short cycling malfunction being experienced, but it seems counterintuitive to use a heavier buffer when the problem is evidently insufficient BCG movement that prevents picking up the round from the magazine.

Comments?

What is the gas system length?

I think there are some 300blk barrels out there with a carbine length system. From what little research I have done, the much shorter pistol length gas system is pretty much required to run subsonics reliably.

Of course, all the rest of the criteria still play a role. Suppressed or not, buffer weight, etc.

January 22, 2026, 10:24 AM

Crockett040

quote:
Originally posted by IndianaBoy:
quote:
Originally posted by sigfreund:
I can’t provide a lot of details about this question (it’s not my gun), so I’m looking for the best guess/advice I can get. A short (~11") barrel AR type rifle chambered for 300 Blackout that I do not believe has an adjustable gas block does not cycle properly with some loads.

This is the answer.
The gun fires and ejects the fired case properly, but the bolt does not cycle far enough to pick up and chamber a round from the magazine. The problem occurs with what I believe is a PSD 220 grain FMJ subsonic load, but not with Hornady Black 110 grain V-MAX ammunition that functions fine. The advice given about the problem was to install a heavier buffer (exact type I don’t know), and that was tried without curing the problem with the PSD ammunition.

I don’t have a lot of experience with the 300 BLK cartridge or with the type of short cycling malfunction being experienced, but it seems counterintuitive to use a heavier buffer when the problem is evidently insufficient BCG movement that prevents picking up the round from the magazine.

Comments?

What is the gas system length?

I think there are some 300blk barrels out there with a carbine length system. From what little research I have done, the much shorter pistol length gas system is pretty much required to run subsonics reliably.

Of course, all the rest of the criteria still play a role. Suppressed or not, buffer weight, etc.

This is the answer. Subs will not run relaibly unless a pistol legth gas system is utilized

January 22, 2026, 11:58 AM

sigfreund

Sorry I didn't reply earlier, but I don't know the gas system length. I suppose it could be carbine length.

The question is good to know if the owner decides to do something to make shooting the subsonics reliable. I doubt that because the supers work fine, and for any serious purpose that's what matters.