To my surprise, my hardly shot higher-end carbine had five deep impacts on the face of the buffer. This surface should never touch the pin if the rear of bolt/buffer face relationship is correctly dimensioned and the drilled blind hole located in the threads of the upper receiver is located in the correct place. The common fix is an easy one...purchase an offset retainer pin which allows the face of the buffer to extend further forward toward the rear of the bolt. This creates a relationship wherein the rear of the bolt keeps the buffer from using the pin as home.

There have been occasional reports of broken retaining pins winding up in the fire control group, with jamming effect. The fix is easy, cheap, and worth looking into.