I don't know enough about casting to say one way or 'tother about that one , REM.
I do know that I cast some REAL 320 grain bullets out of wheel weights and , durn, they were hard to get started. And hard to punch down the bore of my Trade Rifle.
I cast some more out of about 300 Hornady .44 round balls a buddy gave me when he sold his BP revolver ,and I could start them with my thumb.
I just ordered a hardness tester for my homecast bullets.
I not only cast for my MLs , but also for a couple of my cartridge shooters.
I figure the softer the better with MLs.