I've had blue balls when casting overly hot, but never frosted ones, with pure lead. Frosting comes from antimony in the mix and Steve's right, the frosting doesn't hurt the shooting capabilities of the bullets. All of my modern high velocity alloyed bullets are evenly frosted all over.
; I've been casting for a lot of years, well over 1,000 pounds of lead has gone through my moulds and I've never had to cool a sprue plate. When fast-casting with alloyed metal and iron blocks, I've had to singe them onto a wet towel at times to reduce the heat, but never just the sprue plate. I think that's a lot of the problem.
: 700F is not hot enough for pure lead. The pictured bullet shows that. When the lead inside the mould takes to long to harden, I set an aluminum set of blocks on a steel plate for a "few seconds"- as in count to 4 or 6. This is enough to suck the excess heat from them. Too long on the plate, and the mould cools to much.
: Martin - by the sounds of it, you are continually cooling your mould as you are casting and slowing your casting. You should be able to cast 30 bullets before the mould gets too hot - keeping a steady rythem. In 1 1/2 hours, with 200 cast, your rate is pretty good, but not enough heat. Wrinkled bullets shoot about as good as they look.