Cast Lead Thread ?

[JD300]

Hey all I was lucky enough to have a mate give me a bucket of Wheel weights for some casting.
I have a stack of pure lead, flashings /pipe etc and some large counter balances I rescued from a shearing shed we pulled down years ago.
Now it's starting to look like the counter balances are not pure lead as I assumed they would be, Based on no knowledge at all lol, just an assumption that back in the day it would be the cheapest and easiest to get hold of.
Has any one come across them before?
I'm picking they may be just some random mix.
I have done the pencil test and they seem to be 2b same as my wheel weights.
Does anyone else use this method? what is the appropriate technique?
What Brinell hardness is everyone using for there hunting projectiles?
Ill be casting for 45-70, .223, .308, .303
Big clean up the other night getting it all ready and clean for use.