Getting 1'' groups at 100 yards with a mosin is much more than anyone would expect. My stock mosin gets 6-8'' at that distance. I would say don't modify it any further!
Not really that hard if you get one with rifling & use decent ammo but the norm is 3-4" for your run of the mill example. If you are getting 6-8" there is something wrong with the rifle or the shooter.