View Full Version : CMMG BHOA Issues

03-07-2011, 8:34 PM
I've been doing a lot of experimenting with the BHOA. I have one lower that it just doesn't want to function reliably in have tried different bolts, different BHOA's different rails. Even an experimental bolt and BHOA sent by CMMG. Still not reliable.
So I went back to the basic operation.
Bolt catch spring pressure seems to be the biggest cause of BHOA failure. The mag spring simply cannot overcome some bc springs.
I put the o-ring around the BC paddle. It worked every time. That confirms the spring pressure problem
For a dedicated .22 lower, I would recommend trimming the BC spring. No more that 2 coils. Try one coil first.
For a 5.56 lower, use either the O-Ring or trim the spring, but be careful. You don't want the 5.56 locking back when using 5.56 mags and rounds.
Dave N

03-08-2011, 6:23 AM
Awesome fix/idea.

03-08-2011, 7:19 AM
I can't take credit for the idea. CMMG passed that on to me as a quick fix or to see if spring pressure is the issue.

03-08-2011, 3:44 PM
I bought a Tac Sol .22 upper last year and put it on a Spike's lower with a DPMS LPK. I then purchased an Aero Precision lower with a Palmetto State Armory LPK and a CMMG M4 .22 upper this year. When I mounted the CMMG, the BHOA would not work. I then tried the CMMG on the Spike's lower and the BHOA worked like a charm. So now the Aero wears the Tac Sol; that was an easy fix but it does illustrate that different LPK's can/do make a difference.

03-08-2011, 6:02 PM
I pulled the bolt catch this morning, clipped 1.5 coils off the spring. It works every time now.