The problem with a Mosin is that it's not really safe to rechamber to a cartridge with a longer base-to-shoulder length than the stock 7.62x54R. Many years ago a company rechambered Mosins to .30-06. The end result was a very unsafe rifle as there was very little material left in the forward part of the action due to drilling out for the longer shoulder. Bone stock, they're a very strong military action, but because of their short receiver, it's a bad idea to rechamber them for a longer cartridge.
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