Not sure how or where it came or what for that matter. But has any one had something get in bolt lug an cut the crap outta it? Not sure what it was. Was shooting a tournament an it started opening an closing little harder then normal. Pull the bolt blew out the channels wiped it down 4 rds later it locked and this is what I wound up with. Grooves in lug an in the lug channel. Tryed to use borescope best I could to see. Looks like I just wasted 1100$ in 2 months