Winchester model 100 in 308 haven't tore into yet but looking up the magazine opening looks like there is a bracket on both sides of the bolt which I'm guessing connect it to gas system well one on the back side on the busted off. Still attached to the bolt broke off whatever it connects to can't see back in there till I get it apart. I know this is a 1961 rifle and had the recall done on the firing pin is this common to on this rifle I've had this one maybe five years now and I know over five hundred rounds since I got her and until now perfectly functioned. Anybody familiar with this model? Right now can't even get bolt open locked up tight with last case still in chamber where it didn't cycle after fired. I'm a newbie here on site can't post pics of it sorry