We have several ways here in the shop to tighten actions. In the past I put up a pictorial of replacing the hinge pin. In a search for additional methods of invisible repair we have developed the following process which is applicable to most barrel types, though not chopper lump barrels. We begin the process by carefully measuring both the gun and the barrels using both micrometers and an optical comparator. Once we know the location of the hook and how much material needs to be added we have the hook welded shut. While I can TIG weld moderately well, I contract this part out to an expert welder. We then cut the hook in it's new location and hand fit the final couple of thousandths of an inch using the traditional smoke and fit method. The result is a completely invisible repair and one that gives excellent contact between the hook and the hinge pin.