Not to nitpick but interested and confused... the Ruger MK1 is a .22LR semi-auto pistol. Never chambered in .257bob. The Ruger M77 bolt action repeating rifle existed but then the Ruger 77 MKII came out and so I think you might be referring to an original M77 as a Mk1. But... there's also the Ruger Number 1 which is a single shot break action and if you had one of those in .257bob, well then I'd be right interested depending on date of manufacture.