Rottweiler, I am new to this powder coating fad, and intend to become a faddist soon
There are two factors concerning melting. One, as you point out is temperature. The other, dwell time. Sure the powder gases become quite hot, but the short time they act on the coating may not be enough to melt/strip the coating from the base of the bullet. The best way to find out, I suppose, is to mine one of the slugs from an appropriate medium and inspect...