On another forum years ago the conversation was on dent removal and I had replied on a question about what I do. A gentleman replied that he was a gunsmith for 40 years and he suggested to apply a little heat in the area of the dent, just enough to get it warm. His theory was that in doing so you were moving some of the molecules of the steel around and would help in raising the dent. Ever since then I have used heat on any gun I get that has a dent or so. Never enough heat to melt solder which is about 450 deg. just warm to the touch.
