I was shooting some factory 300 blackout today. Winchester 125 grain jhps to be specific. I felt something smack me in the shooting glasses and could not figure out what it was. I gave up when I could not find anything. The casing looked fine and everhthijg functioned correctly. I fired another round and the rifle did not cycle....weird so I pulled the charging handle and ejected the casing. All looked fine, so I pulled the rifle apart and found that the damn adjustment screw from my JP D2 gas block had blown off!! No clue where it went but it left a heckuva scratch in my lense.