ok, here we go.
I've been monkeying around with one of my ARs for quite a while now trying to cure a failure to feed issue. first off, the rifle is a Core15 (upper, lower, barrel, buffer tube).
Last month I sent the upper assembly back to Core15 in Florida for them to diagnose the problem. Along with the rifle I sent all of my testing notes and examples of the damaged brass.
They sent me the rifle back with a note saying that they polished the feed ramps, fired 20 rounds and that the rifle functioned properly.
... not the case when I put the lower back on and go shoot.
I get failure to feeds every other round, sometimes every round when using magpul p mags. The rifle functions better with the metal GI mags but I still encounter failure to feeds while using them.
HERE is the kicker:
I also own a stock Colt M4 so today I decided to take both rifles out and start swapping uppers and lowers. Here is what I found after 200 rounds.
Core15 upper on Colt lower = functions properly with both GI mags and magpul mags
Core15 lower on Colt upper= functions properly with both GI mags and magpul mags
Core15 lower on Core15 upper= fail
what the crap is going on here ?
has anyone else gone through this crap or am I just the luckiest sack of shit on the planet ?
yes, something is out of spec. my gut feeling is that both the core15 upper AND lower are out of spec and that when the two of them get together everything gets out of alignment.