I imported a couple of shotguns from England a few years ago following the basic procedure outlined by L Brown above. The major exception in my case was I had the firearms shipped to my FFL dealer and we took care of the required paperwork to transfer them to me when they arrived. The FFL dealer,who is a friend, did this as a favor and I prepared all of the initial import paperwork for BATF* approval for him and the Dealer in England took care of the requirements there. However; Patience is required as this took about 6 Months start to finish.
Jim
*You can download the forms and instructions from the online BATF site.
