Model 12
Thanks BBBBILL, think of it this way, these were made from 1912 to the 60's on non cnc equipment.
Bores were drilled and reamed from perfect to a bit off center and the chamber ring was reamed to the line of bore.
All things equal, it was a wonder these things worked as good as they did because of the tolerance differances, the parts were made to take up some of the slop built in from the factory, hand made and hand fit stood for something then.
In most cases everything can be made to work together from barrel assembly to barrel assembly, but some times they don't, and changing a chamber ring won't help because you will ruin the fit and headspace from the first barrel assembly.
On thoes rare ones, different barrel assemblies will fit and function fine on one receiver, all most never happens but there out there.
Two barrel sets are worth more but they cost more also, pick up a good one with a poly choke or a cutts comp on it, there prices are less but in my opinion a better usefull choke option and install it, see how it fits you might get lucky, if not let me know and we will talk about it.
I love model 12's(not the "y" models though). Paul Salchow.