O.K. My understanding tin makes lead hard and resist swaging. Biggest source of swaged lead with antimony and NO tin is fired .22 rimfire bullets. Range around? This would be lead and antimony. Exact alloy I don't know but should be common. Scout camps. Mil. reserve ranges. Etc. Lyman used to have good info on mixing these scrap sources for the alloy you want. Tin also makes the lead flow better and fill the mould. As stated, antimony is common in common lead products like type metals, not that type is too common anymore. Luck. Happy Trails.
We always used 9 parts lead and 1 part tin worked very good.
U S Air Force Korean vet. NRA Member
Fourth fighter wing Kimpo Korea 1952 Fourth but first, the mig killers.
533rd material ,air defence Oxnard AFB 1953-1955
Pastor of the CBCG-Fellowship group Tulsa Oklahoma.