Heres the exact thing he has but without mount of course. He couldnt get that because it wasn't boxable and said that he could not leave his base. Really nice museum piece but it had a slightly bent barrel which we had to straighten.
http://en.wikipedia.org/wiki/2_cm_Flakvierling
Dont do something to get arrested! LOL!
Just calmly tell them you are in the process of getting the permits and licenses and see what they tell you. All that is required is an approved F-6 for military personnel (you are correct?) and I can help you square that. It takes 3 weeks to clear. After that you will recieve a permit, a demil letter with instructions, and a couple F-6A's. If you are sending to your home it will be held at your local customs house and someone wil have to be there to recieve it and sign for it. It will be a duty free shipment so there should be no additional cost, only the F-6A will have to be signed by customs and a copy left with them and you will mail your copy stating that you recieved the goods and they were in order back to ATF.
If you find any bolt action, semi auto, handguns, or any other title 1 guns that meet sporting criteria (and lots of ex-military do) they can be shipped undemilled/uncut for your collection.
Be aware, any machinegun or non sporting weapon that you import will be subject to the new rules concerning imported barrels.
http://www.atf.treas.gov/firearms/112205openletter.pdf
Therefore you will have to demil the barrel on weapons like PKM's, AKM's, DShK's, KMT's, any and all fully automatic arms, etc
If you find a bunch of Enfields, garands, SVT-40's, Mosin Nagants, 1911's, etc then you are exempt from that ruling.