Hello,

First post here so I hope I put it in the right place. I have (or will have very soon) a 10.5" 300 blackout upper I intend to run primarily suppressed and a 16" 5.56 upper I intend to run unsuppresed. Is there a good buffer I can use for both on a common lower? I intend to primarily use the 300 blackout and only have the 5.56 as a backup. If it helps at all, I have a Kaiser X7 Monarch that has a light weight, skelotanized BCG. The 5.56 has a mid-length gas system and the 300 blackout a pistol length. I appreciate any help provided.

Thank you. Any specific brands better than others for suppressed or just in general?

You should look into selectable gas blocks or bolt carriers, Adjustable gas block would work too (less rapid changing of the gas setting).

I don't mind doing that if there was a good adjustable gas block / buffer combination that would work. Again, it will be 300 blk almost exclusively. I just want it to run on the 5.56 if it has to. So would I get the adjustable gas block for the 5.56 or the 300 blk?

Sorry, I wasn't paying attention to you swapping uppers. Tuning your buffer (H2 or H3) for a un-suppressed 5.56, then adding a AGB to the suppressed 300 BO should get you the same recoil impulse. You can then run the 300 BO un-suppressed by turning up the gas.

Ok. Nice. Thank you. This may be getting into another topic but I've seen a lot of sites recommend the superlative Arms AGB. Are there better ones or is that truly one of the best?

Why would you run a lightweight bcg and then add weight in the buffer? Isn't the point to drop weight overall?

Why not use a regular carbine buffer and set the individual gas blocks on each upper to match the lower.

That would take an adjustable gas block for each upper but you aren't adding weight to the rifle

I like not adding weight. You're right, they point of this AR was specifically to twice weight.

Appreciate the help. Anyone have good luck with a particular adjustable gas block? I'll start with the 300 blk.

I use an H2 buffer in my SBR lower. My 556 uppers have fixed blocks and the 300blk out has a Seekins Select Adjustable gas block. Since all of my rifles will be fired suppressed from now on, I got the Aero adjustable gas blocks for the 556 in each barrel length. I havent installed them yet though. The seekins was $113 and has a tab to allow for adjustments on the fly, but the rail still has to be removed to access it. The Aero was only $48 or so and is more of a set it and forget it.
The adjustable bolt carrier groups sometimes have issues in 300blk out.
Your usage will determine what you need. I wanted to be able to shoot anything (subs and supers suppressed or unsuppressed) so I went with the additional features on the Seekins, although I can't think of a reason why I would be shooting the 300 blackout without a suppressor.

One of the touted benefits of the A5 system was that the operational envelope was wide enough to use one lower with an SBR, or a rifle, supresed or not.  That might be something to look into.

Personally, I fit my rifles with an A5H0, turn the adjustable gas as low as it will go and function reliably, then upgrade to an A5H1 then A5H2, keeping the lowest weight that will reliably operate.  This gives me the least felt recoil with the least moving mass using the least amount of gas possible.

This is also very good advice