We tend to automatically think everyone is using pure or at least plumber's PB - ie: 98.6% pure lead.
Sometimes salvage places, where some folks buy lead, sells re-claimed battery lead as pure. It is far
harder than pure, even likely harder than the old crimp-on WW.
Heed Taylor's suggestion on the soldered joints - of anything. This also goes for the telephone line junctions
of old. There were pure lead, except for the 50:50 lead-tin soldered joints. I used to save those, chop them out
with a double-bit axe, for high velocity rifle and handgun bullets.