Well, hell. This puts me in a bit of a spot, I've got a custom rifle being put together right now. My riflesmith told me originally that he considered it a "repair job" since I sent him a Mauser action. We'll see how that goes, he's on vacation right now and won't be available to discuss this until next week.
Heck, I've got a 60 year old receiver with a barrel beside it because the gunsmith passed away before he could cut the neck and throat. Now getting a gunsmith to cut the neck and throat and mount the barrel becomes an ITAR regulated activity.
Idiocy of the highest order, and likely to be struck down in court if Congress doesn't overturn it before that.
