Although The washer or shim fix is widely used, it is a dangerous adaptation unless properly tested for bump fire. Aside from banging the butt on the floor you need to chamber a spent casing and pry up the rear end of the bolt firmly to move it as far as you can to see if the sear will disengage. There is considerable slop in the back part of the bolt in some Mosins. I have seen some fire without the modiication.
"War is an ugly thing, but not the ugliest of things. The decayed and degraded state of moral and patriotic feeling, which thinks nothing is worth war, is worse. A man who has nothing which he cares more about than his own personal safety is a miserable creature, and has no chance of being free unless he is made free and kept so by the exertions of better men than himself" John Stuart Mill