Correction, Champlin's USED to have a Alex Henry..
I've never seen a reference to a full nitro 577/500 Mag. Possibly there were NfB proofs? Mine are BP proofed. The Magnum is a 3 1/8" case.
-------------------- "When you see that in order to produce, you need to obtain permission from men who produce nothing; when you see that money is flowing to those who deal not in goods, but in favors; you may know that your society is doomed." Ayn Rand