Keith, I've always said "unless you know bore, you won't know choke size." Some have these choke gages, look nice, sone give thousands on one flat and choke denomination on another. Sticking them into the muzzle will only give you a reading. If we assume .730 is bore and if the bores were honed from the forcing cone to say 15-20 inches from breech to remove some pitting and are now .740. If your choke gage is showing you imp.cyl say .010, you really have cyl.

This is very important in older guns and also in some of these European guns.

David