Schwing, "The Browning Superposed" on page 69 says "The company would rechamber the Superposed for 3" shells". I doubt the guns were returned to Belgium or reproofed. Browning had an extensive facility in the U.S. at the time and I believe that virtually all repairs and modifications were performed at that facility. I agree that recoil in 3" 6 3/4 lb gun would be fierce. However there is no significant increase in pressure with pre war 3" loads, and the stock bedding system of the Superposed is one of the best and resists recoil without splitting for many tens of thousands of rounds in most guns.
