I measured five XX Lefever frames and every one of them were approx. 1 1/32 between center of firing pin holes.Guns weigh from 20 ga. 5lbs 14 ounces to 16 ga. 6 lbs 12 ounces. If the barrels will interchange and can be fitted to original frames you will sell many more sets i believe. If the barrels were put in production there would be some ordered even though the frame and forend would be made later. Just my opinion. Bobby