Bismuth has been bandied back and forth on here quite a lot on its usefulness, but one thing I notice that has not been addressed is bismuth expansion.
I'm looking to get out of using lead, and that got me onto here looking for alternatives. Bismuth alloy caught my eye, but I also noticed that supposedly, bismuth expands about 3% while cooling.
I shoot civil war reproductions with minie balls, and there isn't much space for expansion in those bullets. An Enfield is .577, and Lee molds are .575; even a hair of expansion is going to cause issues.
So how do you stop the bullet from expanding? Do you just fill the mold and then let it sit there, closed? Bismuth crystallizes, from what I understand, causing the expansion, so would keeping the mold closed until cooled prevent that from happening? I've done a bit of googling but 99% of things online about bismuth are how to get it TO expand, to make those neat crystal formations. I'm trying to get the opposite. Would alloying with tin or antimony reduce that?
Has anyone experimented with minie balls before? I don't mind doing my own homework, and I have some bismuth on the way, I'm just hoping this isn't a wild goose chase. As much as I love shooting my old rifles, I really hate how downright dangerous lead is to work with. It's a shame the best bullet material on the planet, just so happens to be a neurotoxin!
Any experiments, or educated guesses, are welcome. I'll be posting my own results when I get it cast down, I plan on casting a dozen minie balls as normal (fill mold, open mold, smack'em out), and then making another dozen with a closed mold, which is going to take forever.