Lower out of spec causing bolt catch failure to engage. Need a solution.
I have an older DD lower that has given me sporadic issues over the years with failure to lock back. I blamed cheap ammo and p-mags for a long time, but because it was a rifle I shot little, I never really dove into the issue.
This summer I am taking my son and two of his friends out and I was getting the rifles zero'd in. I decided to find out what was going on with the rifle. Factory DD lower (BCM FCG added later). Gave me issues with failure to lock back with a carbine set up regardless of buffer weight and now with a rifle extension and buffer. Did some upper and lower swapping and everything pointed to the lower as the issue.
I took a look at the lower and the issue is obvious. I'm angry at myself for not spotting this early. I was to fixated on the issue being a short stroke problem.
For local public range use, I use Hexmags as they are a cheap easy 10 round California friendly solution. I have plenty of other mags, but the hex mags don't attract attention.
The lower is dimensionally out of spec or at least on the far end of tolerances and/or the cut for the bolt catch is poor and allows for too much front to back play. The bolt catch measures within .002 of all my other bolt catches (in other rifles or in the spare box).
On the plus side, it looks like GI mags are OK, but my pmags and hex mags are a no go and that's a frustration.
DD lower with hex mag
DD lower with pmag
DD lower with GI mag
My other lowers all look like this:
BCM lower with hex mag
BCM lower with GI mag
Does anyone make a quality catch with a longer nose? I recall a post from a few years ago about someone modifying a RRA 9mm catch, but does heat treat become an issue? I swapped in a Colt bolt catch and a couple of others from my spares and while some are a fraction better, all are still too short for 100% reliability.
Being in California, replacing lowers can be expensive and PITA. All my lowers are from before the rifle registration in 2014 and I want to keep it that way.
Last edited by mrbieler; 07-06-19 at 13:01.
- Jeff
“Every record has been destroyed or falsified, every book rewritten, every picture has been repainted, every statue and street building has been renamed, every date has been altered. And the process is continuing day by day and minute by minute. History has stopped. Nothing exists except an endless present in which the Party is always right.” ― George Orwell, 1984
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