i have a mosin nagant 91/30, everytime i shoot it the spend cartridge gets jammed inside the chamber and it won't eject. i end up having to drop the cleaning rod down the muzzle to unjam it. the headspace is good, the thing that boggles my mind is that if i don't fire the gun, the cartrige ejcects fine(unfired) but once i fire it, it gets jammed. does the brass expand when fired? i use mostly surplus ammo, but i used store-bought ammo and had the same problem, anyone have any idea what the problem could be?