I sounds like the one barrel has excessive headspace. The 12 gauge rim area on the subgauge tubes was machined to a standard dimension and the one tube could be driven deeper into the worn chamber by the firing pin fall. Shortening the firing pins probably reduced the tendency of the subgauge tube to move forward but will not allow the pin to strike a 12 gauge shell hard enough to go off consistantly. Briley is probably going to machine the barrel(s) for headspace rings to bring the gun back into spec.
Bill Layman
