Not saying this' the world's best solution, but had a big pile of heavily dented 303 brass that had built up over the years - big crosswise creases in the cases making chambering difficult, case mouth and shoulder deformation kind of thing.
Was curious if they could be salvaged, so put a mild load of powder, cotton fluff filling packed over the powder to keep it from detonating, and beeswax plug the diameter and length of the neck. Marked the damaged areas with a permanent marker so I could check them after. They fireformed quite well to my surprise, even with just the beeswax plug and cotton. Sectioned a bunch of them across the previously damaged area to see if there was any noticeable thinning, cracking etc but didn't find anything on any but the absolute worst cases that were almost banana shaped to begin with and had to bend them straight to work, which is pretty understandable. There's almost certainly some sort of embrittlement from being worked though, so it's one of those things that the value of the brass has to be assessed against the likelihood and implications of a failure.
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