I think most foundry hardball alloy is 92% lead, 6% antimony and 2% tin. I understand that the basis for this blend is more for durability for shipping as is the hard wax lube found in commercial boolits over shootability considerations. I'm sure there are other answers. The Lead Alloy Calculator on this site lists that same blend ratio and says the BHN is 16.
Description Tin % Antimony % Arsenic % Copper % Silver % Lead % Hardness
Hardball Alloy 2.00% 6.00% 0% 0% 0% 92.0% Brinell 16
I have cast straight lino for .44 Mag and it shot well. It went diagonally though a 225 or so pound sow without shattering, unlike common knowledge said it would but it did not expand. Entry and exit holes looked the same to me. More recently I have been gravitating to softer and softer alloys.