I use a Dremel tool with a cutoff wheel to slice the head right off. I then peel off the stub and finish cutting the rivets down flush with the trunnion. I really don't care if I scratch the part of the trunnion that goes inside the receiver, since it will never be seen anyway. Finally I use a centerpunch to smack out the short rivets, then use a 1/8" cobalt bit to drill out the long rivet. Usually I'm done in an hour.