I'd really like to have this rifle but the way I read this it was a .257Wby first. Then rechambered to .300 or 7mm Rem Mag then to Mashburn. Either way those bullets would all be a pretty tight fit unless it was rebored as well. Although I bet the velocity #'s are probably high.

“You never need fear a man, no matter what his size. When danger threatens, call on me, and I will equalize.”
Samuel Colt.

�Common sense is genius dressed up in work clothes.� - Ralph Waldo Emerson