Raimey,
This gun was made before the Germans required a proof test. I'm not sure when that date was. There is no gage markings on the barrels.
Bob,
I'm not sure what 14ga shell I have, a or b, but I know it didn't fit. I'm not sure where that shell is at the moment. I'll look for it. I sure don't know what the tolerance amount would be.
Chris