A buddy and I were at the range today and had a little competion with the rimfires. He shoots a 22/45 and I shoot a MKII. About halfway through a brick I noticed the pin that holds the rear sight had worked out about 1/4 inch. When I called his attention to it his was out about 1/2 inch. They both pshed back in with the tip of my leatherman. What will keep it from coming out again?