They use 20:1 allow (20pts Lead, 1pt tin). Brinell hardness, per their site, is 10. That's soft. Not saying it won't work, just softer than I'd select.
BTW, if you want to get an idea of how common casting alloys stack up, check out this site and their notes on lead alloys: http://www.lasc.us/CastBulletAlloy.htm
I mostly use lead wheel weights and water quench the bullets as they drop from the mould. That's a little hard, but they shoot well and are mainly for range use. If I wanted to avoid the quench step and/or had no WW, I'd go with Lyman #2 alloy.
Chris