............so we all agree that that you would ruin an aluminum mold.
Brass will fuze to an iron or steel mold, how do you think they repair cracks in cast iron?
Hickstick, what you're thinking of is bronze, as in brazing. Brass has zinc added to make it bronze. Then, you'd need the steel/cast iron to be real clean and have a borax type flux used at the same time.
Cornbush, I see no reason then to not try it. If you're comfortable with loosing a mold, then why not? If you can deal with undersized and way under weight bullets, it may just work. You may be able to shoot them again if you can recover them in a dirt berm.