Mr. Nash, I am curious about the rim size cut out in your dual fire gun. Most pinfire rims are smaller than centerfire rims. In any event, it seems one rim or the other might not fit properly in the same gun.
I don't have the best caliper, but the rim recess seems to measure about 1-1.25mm, and a 12-bore cartridge fits in it, no problem. I've not fired the gun, but I can speculate that since the pinfire cartridge would not be wholly supported at this junction, split cases might have occurred, particularly with very thin brass. As a typical pinfire gun-case tool was a cartridge extractor, then split brass, swollen paper, broken pins etc. must have been regular occurrences in any case.
