Mike,Justin,
Now I'm completely confused...The barrels are .250 at the breech with a minimal wall thickness of .045 near the chokes...the bore diameter is .740 just before the chokes but from the chambers to the chokes the bore measures a whopping .770...
Although it's stamped 13/1, remember it's a 3 1/4 inch magnum 12 ga, but the history of the 12 gauge magnum cartridge has always eluded me...about the only thing I can say for sure is the 3 inch 12 ga (75mm) has been around since before 1924 because I have a pre-1924 (Belgian) Raick Freres in 75mm. The other bit of information to consider is that the age puts it near the tail end of those first choke boring concepts and trials.
Thanks for any insights concerning this gun and it's very strange bore dimensions.
