Hello, Adam: great to see you here in the Charcoal section! If it turns out you're correct, I'd be glad to help you obtain any such item from the US.

My initial reaction - and this is PURE guess and speculation - was the opposite of yours. My logic was that since it isn't a once-operable firearm that's been properly deactivated in accordance with legal standards, but rather a firearm intended for use, but just lacking that last step: the law would consider it an operable firearm.

However, the more I think about it, the more I'm inclining toward your position.

I think one important point to consider is, what would the law consider acceptable in order to deactivate a once fully-functional, modern replica flintlock pistol? IF (and I'm only saying "if") sealing the vent hole would suffice, then I can't see any legal distinction between a pistol where the vent hole's been permanently sealed, versus one where it was never opened.

Also, UK law - and UK law is in a sense more lenient, in another sense harsher, than US law in this respect - seems to draw a distinction between the inherent capabilities of a firearm, versus the owner's intended use of it.

Case in point: in the Uk, you can own an antique Colt Navy 1851 cap and ball revolver without a license. BUT, if you intend to shoot it, it must be held on a FAC.

Similarly: you can own a cartridge pistol in an obsolete caliber without a license. BUT, if you manage to scrounge up an antique cartridge or two that fits it, your act of keeping pistol and cartridge(s) together is held to be evidence of your intend to fire it: so you'd need to have it on FAC, which unfortunately you'd not be likely to do.

To the US mentality, this is all too tricky! Here, we'd say the gun is either controlled, or it isn't. Whether you intend to hunt rabbits with it, hang it on your wall, or punch holes in paper with it, is irrelevant.

In the examples I gave above, the Colt Navy is simply unregulated (under federal law: state law can vary) at time of purchase. The obsolete cartridge pistol is unregulared if made before 1899, regulated if made later.

Simple and straightforward.

Jim