Originally posted by RIP:
Playing with me, eh?
Don't know who makes the mould?
Don't know who makes the gas check?
.516" to .510" sounds like a happy accident rather than a plan.

Let's try to remember correctly what size and who made the sizing die?
What alloy is that .510"(hopefully)/580-grain RNGC?
It is a beauty.
Already have an NEI mould for 670-grainer that I can use.
Don't want to design a custom mould right now.
Your specs seem fine (if remembered correctly), sort of a universal 500 bullet there.
Thought you had all the details worked out on this one already ... ???
Several around here might be looking for a "turn key" 500 Jeffery bullet mould.