Before the inlines came out I drilled and tapped several side locsfor my self and others for scope bases.Someone used to sell the bit and tap,and I think I got the bases from tc ??.they came in different sizes for the flats on the octanagal barrels.
The best thing is to use a drill press to get the holes straight but I did do a couple with a hand drill.
I remember the first muzzleloader season here everyone told me I was going to get a ticket for useing a scope.So I called the wildlife and the fellow I talked to said he would get one too because he had a scope on his too.