LRBHO failure, 300BLK w/Left Handed Upper

Some time ago I traded for a left handed upper and bolt. I've just gotten around to messing with it and am having trouble with LRBHO.

8.5" Ballistic Advantage barrel
Superlative Arms adjustable / bleed off type gas block
Pistol length gas
Carbine length receiver extension
LEFT hand bolt and upper, both new
Suppressed

I can get it to cycle just fine. But I can't get the LRBHO to work with subs. I've tried every gas setting setting from all the way closed to all the way open. Tried a variety of buffer weights as well.

Bolt catch works just fine with the charging handle.

Ideas?

On lowest setting, where does brass eject?

edit: And, what weights of various buffers and which spring?

NKD said:

On lowest setting, where does brass eject?

edit: And, what weights of various buffers and which spring?

Click to expand...

not sure what you mean by "lowest"....with gas block wide open it's ejecting pretty much back over my shoulder. I can close the gas down to where it cycles, loads next round, with ejection just past 9'clock (lefty upper; 3 equivalent)

odd talking point here that could be useless information.

On the barrel extension they are all right hand chamfer only. You can order A ambi-chamfer barrel extension when building a barrel. BUT you can not add it to a current barrel. Well you can, but you will need to drill a new gas port. Anyhow, it might not be the issue, but you could have a bit of bolt drag and its causing the issue. I do not know as I have never shot subs out of a lefty upper but I do own 5 left uppers.

take it for what you paid for it.

NKD said:

edit: And, what weights of various buffers and which spring?

Click to expand...

Standard Carbine spring with buffer weights from 2.8oz to 5.4 oz, with a couple in between.

I’d call BA first, I had to open up the gas port on my, not lefty, 10.5” from another mfg for sub LRBHO.

Tim said:

Standard Carbine spring with buffer weights from 2.8oz to 5.4 oz, with a couple in between.

Click to expand...

One option,

Knock out the roll pin in the buffer and remove all weights. and re-assemble the rubber end, I did that once to a 16" 5.56mm Ballistic Advantage barrel build, it was the only way I could get it to run.

Tim said:

not sure what you mean by "lowest"....with gas block wide open it's ejecting pretty much back over my shoulder. I can close the gas down to where it cycles, loads next round, with ejection just past 9'clock (lefty upper; 3 equivalent)

Click to expand...

My bad, made that confusing. Mean lowest restriction.

So, 3:00/9:00 seems like plenty of gas. But you have a short dwell time with pistol 7.5.
Might need a little more. Assuming gas rings are in order, etc. Maybe try an empty buffer.