This Heavy Recoil Base Plate becomes a necessity when mounting a "Wm. Malcolm" scope on any large bore rifle that generates a noticeable amount of recoil. In addition to using the factory cut dovetail for the rear sight, this base plate also allows for the drilling and tapping of two additional screw holes, which totally eliminates lossening of the rear mount. (Note: The existing hold pattern of this base will match the rear sight screw hole already in the barrel of some modern Sharps rifle models.) Any rifle .45-70 or larger will require the installion of the Heavy Recoil Base Plate. Also, the barrels of most muzzle-loaded rifles are of a softer steel, requiring the use of at least one additional base screw to insure that the mount stays solidly in place on the barrel.