We ship rifles, locks, and barrels to the UK, Europe, and Australia each month. No problems because muzzleloaders are not classified under the Federal Firearms Bill of 1969 as firearms, but rather as antique replicas. Antique replicas are shipped all the time around the world. Just keep the mind set of Antique Replica when describing the product on the customs form and of course avoid the words gun, rifle, smoothbore, etc.
Now where you may run into a problem is the length restrictions on a box via the US Postal Service. I ship all international items vis the US Postal Service (paperwork is a lot easier to fill out and prices are far more reasonable) unless the rifle is too long to the particular country. Each country has it's own size limits you can check them on the USPS web page. If it's too long to go US Post, then I have to ship it UPS Supply Chain Freight. This isn't too much of a hassle, but does typically double or triple the price.
Again I am either vague or overly descriptive on the customs form depending upon the item. I.E. Barrels are listed as "42" 12L14-B50 Steel Machine Tubing" to describe a York B weight 50 cal. barrel, locks are listed as "Antique Lock" most people will think Door Lock instead of flintlock when they see this, rifle kits are described by item groups "52" curly maple sample wood, brass cast antique lock parts, steal cast antique lock parts, lock screw set". You get the idea. If you need further help, please shot me an email and I'll lend you my shipping knowledge.
