Oddly enough that was what I originally wrote when I made the post. But then I thought, am I remembering correctly? So I did a google search under "brinnel hardness pure lead" and found this link:

http://www.wingshooters.co.za/pdf/articles/SteelShot.pdf

Probably the answer is that pure lead can have Brinnell hardness ranging from 5 - 12 depending on how it istreated with heat. Lead shot is generally made by allowing molten droplets to air cool as they fall. This probably has the effect of quenching the lead making it harder than if it cooled slowly. Anyway, the powerbelts are probably alot closer to 6 than 12 hardness.

Happy Hunting, Phil