Bolt catching on bolt catch .

[Lastrites]

I have never seen a spec for the space between the mag catch and bolt face when the BCG is in full cycle all the way back, but there should be at least .120-.125 minimum space or better in my experience.. Out of spec buffer tubes, poor installation, weak or using the wrong recoil spring will show after doing this test common test..

Bolt face on most ar's are supposed to 1/8" to 1/4" in front of the back edge of the ejection port, if it disappears beyond the back of the port all sorts of wonky malfunctions may occur. On 9mm uppers the bolt face is supposed to stop a 1/4" past the bolt catch.