Very interestiong question Mr. Craven -- Hadn't ever thought about that till now. Could be that you may be able to file one off to the width of a 16 gauge FW reciever without getting into the two screw holes, and then only need to fit it to the Knuckle --- bet the ejector parts are the same from guage to guage. The distance from the hinge to the barrel hook might take some head scratching. The books show the frame dimensions well enough. Would be worth a try? Not a "bolt on" but possible? Dr. Hambidge???? What do you think? Kraft P.S. Going by the drawings in John's book the difference in frame size is from the water table up.