I can't provide qualified advice on this topic but I can provide a case study that is unfolding for me at this time:
I bought a gun at auction in the U.K. for 400 pounds sterling in December. After all the shipping, licensing and fees were tabulated (and converted to US dollars) my sunk costs for the gun and the Queen's government were about $1400. That allowed me to go to step B.
Step B. Since the gun was made in 1887 it entitled me and the seller to less paperwork. It is an antique pre-1897 gun by UK standards (not sure all the benefits but the seller was pleased by this fact for the sake of less paperwork). It is also a pre-1899 arm by US standards meaning it is not a firearm by BATF standards. In short, I did not need to fill out a Form 6 and wait for approval for 60 days, nor did I need to pay duty (>100 years old) nor did I have to hire an FFL to clear it through customs for me.
Step C. Once all these logistics were figured out, the UK government authorized the gun to be shipped out of the country to the USA. After several delays and missed dates, it shipped last week.
Current state: Fedex and customs were idiots and didn't know what they were supposed to do. They stopped the gun at Newark customs and locked it up. (it was supposed to be sent to Chicago customs so I could deal with it) Supposedly, it is going to be forwarded to Chicago next week and if all goes well I'll have it in hand.
The things I have not yet proven:
1. Will the customs officials believe the seller and my record books that the item is not classified as a gun because it was made in 1887?
2. Will I encounter hidden fees?
3. In spite of the law being on my side, will they try to force me to get an FFL to receive the parcel at customs out of sheer ignorance?
4. Will they reject it in ignorance because it doesn't include a form 6 license, even though it is not required?
5. Will it get lost with all these delays ongoing?
6. Will the item be worth $1400 when I get it in hand or did I buy junk to begin with?
I look at this as a neophyte experiment where my tuition is $1400 to gain the knowledge of how this works in practice. I'll have to see how this actually ends up.