In my limited experience I have reached the conclusion I can't decide which I like better between the AK or AR. They are both a lot of fun for different reasons. I don't have any practical resons for most of my guns. I make up a lot of impractical reasons for what I have.

Don't forget the Any Other Weapons. The transfer tax is only $5 dollars, not $200. A pistol grip, less than 18 inch barrel shotgun can be a AOW. I think you can get factory Mossberg shotguns that are AOW. Other examples are pen guns or cane guns.

The ATF National Firearms Act Handbook is a real good free information source. It is the official information. It has information in plain language. If you can talk lawyer speak it includes copys of the regulations and laws concerning NFA. You can download it here-

http://www.atf.gov/publications/firearms/nfa-handbook/