I'm sure there are cartridges for which it could be adapted -- certainly similar-sized rimmed, tapered ones. Anyt other type might involve some pretty extensive and expensive work. But there's absolutely nothing wrong with the 7.62X54R. It's a great round in a great, largely unappreciated, rifle.
Rather than changing the chambering, I am thinking on building a target-customized version. There are still plenty of nice $100 rifles out there that would make a great, cheap base for such a gun, and there are Finnish and Russian-built target rifles to serve as a models. Those who would mock such an idea have never see just how well the MN can shoot...
As far as being on the "safe side", the action is perfectly safe pressure-wise with anything that doesn't exceed the 7.62X54R pressure level. Almost any cartridge from the late 19th century era will be OK from a pressure standpoint (.303 Brit, .30-40 Krag, 7x57, etc.). From an engineering standpoint almost any cartridge other than the original is going to be a challenge in some regard.
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