" I tried to do this and it took so much force with the hammer "It depends on the stamp set, A full set from the local BarginLumber store for 9.99 might not be hardened enough for the steel barrel, Where as a high end $100 set would do the job with just a firm hammer blow,,

I had the choke opened, (actually just to get it honed round and straight), on a 12ga Pardner barrel and simply stamped the side of the underlug "Imp Cyl",,I figgure if anyone get's it in the future they'll see that and get the idea,,
