Rifles with "shoulder hooks" had them for a purpose. I learned this as an offhand m/l rifle competitor many years ago. They are referred to as crescent buttplates, and are intended to be placed on the upper arm, just outside the shoulder joint, not in the shoulder pocket. This requires a little different stance than most shotgun shooters use, with the side of the body more toward the target. The "hooks" keep the hard brass, or steel, buttplate from sliding around on the shoulder. The most exaggerated of all are found on Scheutzen rifles, the ultimate offhand competitive rifle of the 20th century. They are quite comfortable, and effective, when used properly. I had one longrifle built in the Appalachian Po-Boy style that didn't have a buttplate, only a slight curvature to the wood butt. I glued a strip of coarse emery cloth to the butt and it effectively kept the butt in place on my shoulder while aiming.
Stan
