Well that's different.

First you can fly with loaded black powder cartridges, you just can't fly with loose black powder. The correct answer to that question comes from the Airline (not TSA) you are going to fly with in the form of a written letter. If you send a letter ask them for supporting FAA regulations for their decision.

And TSA does not know the correct answer.

It's better to not even ask the question. The airline has no way of knowing what's in the cartridge to start with. Asking questions like this at the check in counter puts a less than knowledgeable employee on the spot and they have express their best judgment. If you ask , don't argue and except the answer.

I have flown all across the country and even to South Africa carrying blackpowder cartridges with out issue.

Loaded ammo, pack it as directed, declare it as ammunition for the rifle you are carrying and answer only the question you are asked. Nothing more. And, it will be in compliance with the FAA regulation covering the subject.

Now that you have given details on your desire, I have a better option for you.

Westley Richards Musket No.2. Also known as the 500/450 Musket No. 2 or just 500/450. Cases made from 32 gauge shotgun brass, 50/90 Sharps brass or buy Bertram 500/450 brass.

Groove is .458. Dies available from CH-4D. 50/90 formed brass available for Martyn and X-Ring service.

You can use a standard .458 barrel.

I have a reamer.

Th cartridge is from the same era as the Martini. It was created by Gibbs and Westley Richard to compete with the 577/450 in the European market for use in Martini's. Several eastern European countries had the Martin's chamber in either the Gibbs or WR version. There are minor differences but on cartridge will fit and fire in another. The cartridge has almost the same ballistics the 577/450.

The No. 2 Musket was made to start for a drawn case and has none of the issues associated with switching over foil case-such as loose charge in large case or lack of neck-throat transition.

This cartridge will fit any action that will take a 50/90 Sharps cartridge.

FWIW my I. Hollis and sons, Number 2 musket will go in the blind with me this fall for white tail.

I have a friend in Europe who used my reamer to cut a a chamber for his rifle that he use to shoot in long range Matches at Bisley in UK. He doesn't always win. They guy that does win has to shoot real well to beat him.

Tell me which gunsmith you are using and I will send him the reamer. When he is done, he can send the reamer back to me. Then you will owe me a bottle of Talikser 18.