You must have some wheel weight lead from before 15-20 years ago. The antimony in wheel weights now is around 3% if that. Years ago they had as much as 15% and were very hard. With you going 50-50 you should be bringing the antimony ratio down to just under 1.5% which would bring you in at 8-9 B at the most. If they are super hard after air cooling for just a couple of days then you have an exceptionally high amount of antimony. With a 95% lead, 3% antimony, and 2% tin it will take a good amount of time for them to air cool and harden up, week and a half to two weeks, but they will reach a pretty good hardness for that .45-70. Too hard will cause pretty severe leading because they aren't obturating and allowing gas to leak around the bullet at extreme temps. What those would be good for though is in a sabot out of a muzzleloader when going after something that could eat you. Obviously good penetration. I wouldn't shoot them out of that .45-70 anymore unless you want to deal with leading cleanup.