I have a Ruger all stainless M77 Mk2 I think its called in .338 Win,its basically identical to the pre-64 Winchester controlled round feed, yes you can chamber it upside down, great rifle after I tossed the too narrow plastic stock that came with it and mounted a Hougue overmolded rubber over fiberglass, great stock with aluminum bedding for the action, and the scope mounts are super strong like a Sako.