use a giant chunk of lead if you got it. It's dense enough to not absorb the blows and won't mar the finish of the AR. I also suggest to do it on a concrete floor. If you do it on a wood bench the bench will absorb the blows and you'll end up peening the pin over like a rivet. just align the punch on the pin, aim, and WHACK! and repeat a few times to get it started and then it should just fall out. Velocity not mass with get it going, so use a relavitely small hammer that you can really whack with. I find that with a sledge, one tends to decelerate in mid blow. Just remember WHACK!, if you tap-tap-tap, you'll peen it over like a rivet. You can also drill them out and turn the taper pin into a roll pin then tap it out. just becareful not to touch the barrel, and use the smallest bit you can. good luck.