could that have been a firing bin gaping issue? i know some rounds are not built to the specs of the surplus rounds, and the bolt can penetrate hard, or extrude when cocking into firing position enough to fire a round, gaping the pin to be lower has helped with that issue on a few mosins i know had that issue.
and if your looking for parts i can recommend an assortment here or just view my mosin project, i and others have posted numerous addon/additional parts for the mosin
If zombies, i have gone for big guns, will return soon !
Firearms Project(s): TM15:WIDOW 5.56/300