I have not bothered to sort pellets yet, but this video (which I found on Reddit) seems like a solid idea for no (or almost no) cost.
Well that makes sense, I guess heads can't get out of round."John_in_Ma"I doubt he is sizing the skirts, just the head. It looks like the two top plates are spaced up from the plate the skirt sits on allowing just the head to get "pinched".