You might get more replies in the Milsurp section, even though the M/N is a .30 cal WW2 military rifle.
I'm certainly not an authority on caliber swaps so I won't go into any speculation about turning you M/N into a rifle of any other caliber. As far as accuracy goes I've read that 3"-4" groups at 100m is about average with surplus ammo for an original 1891/30, although there are way to improve that, some with no cost at all to the user.