Copper series. The only way to keep the copper coating on them is to slow them down. The only copper that usually stays on the powerbelts is at the base and holds it together.
The all lead powerbelts expand massively. I want to try some of those too.
Opened it up so you could see what i mean about the copper staying together at the base of the bullet. Should have hit it with a flash light for a better view but this will have to do.