Most oddball I've done is making 577 snider and 577-450 MH out of 24 gauge brass shot shells. Was a bit of trial and error annealing the brass enough and sizing down to put the shoulder on it for the martini. If they crushed quick they could generally be salvaged for the shorter snider cases.
Had to stop using them in my snider though, the Nepalese made the chamber a bit too big. The thin 24ga blow out and split on the first firing. Moved to Bertram and have had a dozen firings and still going strong.