Bob, you are, of course, absolutely right. Code requires the use of listed equipment. Someday I might even see that requirement complied with!

Mike, the coals seem to be pretty self-regulating. An even bed of coals = an even heat...and with the clearance you see, it seems to be 'just the right temp.' Best of all, when doing several bends, it is not necessary to "turn it off" between uses.
I think that the hot gasses from the coals help them to heat the pipe more evenly than, say, a radiant heater.

Otherwise, Mike, for some silly reason we seem to have no shortage of empty ammo boxes these days. It seems almost as if the Army is emptying them on purpose.... [Linked Image]