Excellent, your ole' Brno! That's really cool. A gun with history already makes for the best base, I think.

I'm not sure what you mean by "moderator". Is that what we would call a muzzle brake or vented barrel attachment? Do you have a link to the maker?

Sounds like you already have it settled, but for a really bullet proof metal finish, machine paint over Parkerizing/Phosphating is ugly, but absolutely rustproof.