Think annealing might do any good? I've seen some guys talk about using sheet brass before and mentioning that it has to be annealed before it can be made into caps.Well, the 28 gauge copper came in. Glad it was cheap. Too thick, too hard, and brittle. When I tried to make a cap with it, it broke off down inside the die and I had a dickens of a time getting it out. Back to aluminum cans unless I can find a much thinner piece of copper.