i recently bought a used s&w 629. where the fireing pin comes out of the back part of the frame, it appears to have maybe a bushing of some sort? i am not sure of this, but anyway, it is like that part protrudes slightly, and when the gun is fired, the primer becomes concaved by it. i handload, and this concave thing makes it more difficult to "read" the primers for signs of excess pressure. any idea why this is like this?