Snot on a door knob is REALLY slick, too!
Voice of experience.
I was gonna post a dissertation on what's wrong, but bigedp51 did the whole job better, with a couple of pictures, thus saving me a hour's typong and making misteaks all over the place. MUCH better, too!
For the actual smoothing/grinding of the cocking-piece, I find that I get good results with a flat Arkansas stone, coarse on one side for rough work, fine on the other side for final smoothing. Buck-sixty-nine at Princess Auto, plus two drops of oil stolen from the leaky can in the back oif the '71 Ford van.
Works best with the stone lying on a flat surface so you can put a bit of weight on it if you need to. Really speeds things up. AVOID the temptation to use the Dremel tool!