AR charging handle / bolt catch question

[StevieP]

(X-posted in General Discussion, too, but thought this may be a better place for this thread)

I have two AR-15's.

First was built with a NES group buy lower, has RRA complete upper, and I think a RRA lpk. BCM Gunfighter charging handle.

New build is a FrankenRifle. Anderson lower & LPK. Wilson upper. Brownells BCG. DPMS Charging handle.

With my old rifle when I pull back on the charging handle, I have to manually depress the lower part of the bolt catch button to make it engage.

With the new carbine, just pulling back on the charging handle locks the bolt back. The only time I press the bolt catch button is to release it.

This seems more like the way I figured it *should* work. So maybe I built the first gun incorrectly and have been doing it wrong for years? Put the bolt catch spring in wrong??

But then I put the old upper on the new lower, and the "problem" followed the upper. I still have to depress the bottom part of the bolt catch to make it lock back.

How is this possible? Anyone have thoughts on what the issue might be, if it follows the upper??

 

[StevieP]

Disregard. Got the answer in General.

With no mag or a full mag, you have to depress the bottom portion of the bolt catch.

With an EMPTY magazine, it locks back on its own.

I hadn't picked up on the difference as I was just doing function testing of the new gun with an empty mag.

 

[Marty McFly]

Holy necro thread! I had an out of spec (but there isn't really a spec) cmmg bolt catch. Put in a cheapo ar stoner catch to check and it works perfect . Seems cmmg is a problem. Why didn't they fix this