GregSy, good catch. The chart is in fact INCORRECT. It is incorrect on nearly all entries. You caught it and I made a comment on the PGCA site about the error. The correct pin separations are on page 527 of The Parker Story. There are several errors in Remington charts and memos about Parker shotguns. This is one of them. The #1 and the #1/2 frames in fact have identical pin separations at 1 1/16". An actual Parker Brothers memo states that #1 frame barrels are to be used on #1/2 frame guns.