Tin has a much lower melting temperature, so be careful not to overheat it.

The specific gravity of lead (Pb) is 11.34, which tin is 7.2 to 7.4, That makes tin 64% of the lead weight. That makes the lead ball 1.55 times the weight of a tin ball, same dia.

A tin ball should cast just fine, but perhaps there might be some "soldering" of the tin to the mould, of casting straight tin, I do not have ANY experience.

https://www.google.com/search?client=firefox-b-d&q=Tin+melting+temperature