How efficient the hammer puller is depends on what you are slamming the hammer down onto. Slamming on anything but solid concrete in my opinion and experience is asking for poor results. You don't want to hit anything that will absorb the hammer shock. I put many a dent on my wood work bench without moving the bullet. Went outside and slammed down on a concrete stepping stone pad and out came the bullet first try.

300 rounds I bet could cause a blister. Wear a glove for sure.