As far as hyperinflation goes, it will be quite different from 1930s Germany. The RF produces the grain it needs (particularly as they won't be able to export via the Black Sea going forward). Rail seems to still be functioning in spite of the sanctions on precision bearings - so an issue long term. Similarly, they have enough petro for the time being, although they'll be unable to reopen shut-in wells in the permafrost - so it's going to be an issue eventually. They will probably establish price controls for grain and fuel (at least for farmers) to avoid food riots, which I expect to work short term.
On to the Mosin. It's not a bad rifle, about like the M1 (military version of the 30.06), with a lower effective rate of fire.