I have an 11.5” BCM BFH upper. No adjustable gas block (no intension of installing one either). Running it on a pistol with Daniels Defense chrome bcg, H2 buffer, and Springco white spring. Runs just fine unsuppressed. Ejects about 3:00-4:00. Put on my suppressor, and still ejects about 3:00, but only ejecting maybe a foot out. In my mind if it was “overgassed”, you would think it would eject slightly forward and out always. But that’s not the case. Is it dwell timing issue? Should I go H3 buffer? Heavier spring? Locking back on empty mag fine.

I have another BCM 11.5” upper on my SBR, and it runs fine suppressed with a standard H buffer. It is also a different barrel (CHF) and was made like 5 years ago.

What is the gas system length?

How does bolt velocity feel? What do the cases look like?

Carbine Length gas system I believe. Bolt velocity didn’t feel abnormal, and brass looked ok. Was using American Eagle 5.56 55gr fmj. Haven’t ran anything else through it yet. Just seemed like the brass was trickling out, without any significant velocity or distance. I was planning to picking up an H3 buffer for a different build. Might have to try it. Was hoping to avoid that game of trying different buffer weights.

Do you have any actual malfunctions, or are you just concerned with ejection distance?

Honestly, if it's feeding, firing, and ejecting just fine, and locking back on an empty mag, then it ain't broke, so I wouldn't try to "fix" it.

^what he said.


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C'mon guys. Help the dude out. Every guy here like his gun to run the way it's supposed to. Would you rather drip out or skeet skeet out?


So you've got nearly identical uppers on two guns but one has a H and the other has an H2? Are you using different springs and such in that H buffer gun too? So...if everything is nearly identical except for the buffer weights, why not just swap buffers and see how it runs with the H buffer you already have?

I’d rather skeet

As long as it's reliable, I'd call a 1-foot ejection pattern a win!

Again . . . as long as it's reliable.

I wouldn’t say they’re identical uppers. Different barrel specs, and 5 years apart in production. Could be different gas port sizes for all I know. Also different bcg’s. I’d prefer a bit more ejection on something, than a week dribble. Haven’t ran enough rounds through it to say it’s “reliable” suppressed.

Just trying to determine if it’s overgassed symptoms, dwell time, or something else. Leaving it be isn’t the answer I’m seeking guys. Dwell time or overgassed seems like a parts longevity issue.

So how much can you make “like for like”? Can you get to the gas port and measure it?

Unfortunately the gas block would be a real pain in the ass to get off. Don’t have the tools, vise, or a workbench these days.