...Another melt test, is to take a sample know lead piece and unknow alloy and lay them in the bottom of a flat pan and slowly bring it up to temp. In most cases, the lead will melt before the alloy..
A lead/tin alloy will ALWAYS melt before pure lead. It's the main reason tin is alloyed with lead for bullets, it lowers the melting temp. It also increases the fluidity of the lead, causing it to form those intricate corners of the lube grooves and sharp corners at the base. The addition of antimony is to harden the alloy.
Black powder shooters find they have to run at much higher temps to get well-formed round balls and conicals when making them of pure lead.