Be aware that the usual practice was for a very TIGHT fit to the bayonet. Russians didn't remove and reattach the bayonet all the time, like we (and most other armies) do.
Mosin bayonets were intended to be fixed, all the time. Basically put on the rifle once, and left there.
If you want a bayonet you can attach (fix) and dismount easily, you are going to have to do a little metal work to the bayonet (NOT the rifle).
Good Luck!