Wrapped up an AR build (.223/5.56) using Aeroprecision upper and lower.  Everything went together perfectly and the upper/lower fitment is perfect.  A function check confirmed the rifle functions as it should.


The only issue is with bolt catch.  It’ll hold the BCG (Aero as well) on an empty mag but won’t if you try manually.  I tried different upper/lower combos with a BCM build and everything worked perfectly.  The only thing I can figure is the Aero bolt catch is out of spec.

Any thoughts?

Seems odd that it will work on an empty mag and not manually.

However, i will add my input.

I had a lower that would not hold open manually or on an empty mag. After taking a bunch of measurement, and trying multiple bolt catches, it was determined that the machining in the lower was shallow for the bolt catch.

I took a dremel and removed material from the back of the bolt catch on the surface that cants into the lower where the spring is.

That solved it and the lower is still going strong.