crow_feather, you need a little metal cup, called a flash-guard, on that nipple. They direct the blast, and the cap fragments away from the gun, in whatever direction you choose. I have one on my .58 Enfield. Works like a charm to keep those big musket cap fragments out of my face, and keeps the lock area clean, too. I can't see why it wouldn't work well on an underhammer. You can point it away from your arm, and direct everything down, foward, and to the right, if you shoot right handed, or left, if that is what you need. I got mine from Cabela's, but I don't see it in the current catalogue. I think it was made by Ted Cash, really don't remembrer, though.