As far as the BATF is concerned the action is the firearm. For that reason, buying one requires following all the same rules as buying a complete gun. In particular, they can't be sold mail order, unless by transfer through an FFL holder. That's why you don't see them being sold by all the same places that sell barells, stocks, etc.

My guess is that you're going to have to find specialist gunsmiths (Brownell's might have some), and arrange for them to ship to a local FFL holder who will then transfer the action to you (for a fee, of course).

That's fine by me; the purpose of this exercise isn't to circumvent the law, but rather to put together something exactly as I want it.

OK...thanks. I'll check out Brownell's. Any other places like that come to mind?

Yep, gun shows. I got a Parker Hale 1200 to build a rifle for my dearly departed wife. Made a fine rifle.

mzimmers.,
Not too sure but seems to me I remember something about empire rifles having their own quality mauser actions that were made for them, you might check with them.