Hi Martin
To be honest, I don't use the 30-1 alloy myself because I use wheel weights. I get them free, so why pay for alloy?

However, I can't say that WW alloy is the same in Argentina as it is in the USA.

I used to run a company called Cast Performance Bullet Company in Riverton Wyoming. We made millions of bullets for various handgun and rifle calibers. I started the company (named
Hi-Performance Cast) in Gardnerville Nevada, and it was later moved to Yerington Nevada, and then to Riverton Wyoming. I give over my part of the company to a friend when it was still in Gardnerville, and he changed the name to Cast Performance, and then moved to Riverton Wyoming after I had moved to Shoshoni Wyoming.

Anyway, I only tell you this to let you know, I have learned a LOT about cast bullets and how to make them. I took the company over again in 1999 because of some difficulties that they were having, and the investors asked me to take it again, and get it back on track. In the time I was a partner, consultant and/or manager of that company we produced millions of bullets for sale all over the world. Federal Cartridge company used them in their Premium line of handgun ammo. The called them "Cast-Core" bullets, but we made them for federal.

When I left I turned over control to Kelly Broast who was my day shift foreman. He became general manager. After that He and his wife bought the company from the investors and it became theirs. About 2 years ago it was sold again to a man in Oregon.

Coming back to your question, tin will NOT make your bullets too hard for muzzleloaders. In fact, tin alone will not harden a bullet much at all. It does, but not enough to matter much. It need to be combined with antimony before it starts to make the bullets much harder. Tin in a 1-10 mix with lead will harden a bullet initially, but the alloy will work soften if it’s disturbed at all, so it’s deceptive to “harden” with tin alone. Tin’s main function in such allows is simply to cause the mold to fill out, so the bullets weigh the same.
Now if you combine tin with antimony you start to get much harder (and Daryl is right, the frosting
in a bullet comes from the presents of antimony and tin, not tin alone), but Led/Tin/Antimony also will work soften to a degree. The secret to very hard and TOUGH alloy that is not brittle, it to include a trace of arsenic, silver and copper. My alloy was mixed to include all 6. Our alow came at 22 brenell hardness, but unlike lino-type, it was not brittle, and would not break up if it hit heavy bone.

Now, that amount of hardness is not bad for muzzleloaders, but it’s hard to load, and so I don’t recommend it for most applications. For your REAL bullets I would mix 96$ lead, 2% antimony, and 2% Tin. Cast them at 750 degrees and let them air cool. Thake the time to over-pour the mold and let the bluuets cool slowly in the cavity. It's slower, but you get close to 100% good bullets, and no rejects. So your hourly production is higher over-all.

We did make some bullets for muzzleloaders that ran the same alloy and the same hardness, but they were made for “bullet rifles” and were sized and rifled to fit the individual rifles. The worked extremely well, but they were overly specialized, and there was not enough market for them.