Those little 24's are great squirrel and rabbit guns! My first gun was a model 24 in .22/.410 that Dad bought used in 1966 for me. I've still got it and a .22M/20 gauge and like you I'm having trouble with the sights these days and I've been thinking about scoping them.
I was concerned that the groove type mounts wouldn't stand up the recoil on the 20 gauge though. What mounts did you use on yours and anyone who has scoped a 20 ga., Any problems with the mounts slipping?
