Jerry go to this link
http://www.atf.treas.gov/firearms/faq/faq2.htm#b17
for info on how to get one. It's easy and usually fast. The advantage of one is of course buying direct of any listed Curio or Relic from any where in the US, You can also fill out a form 6 and do an occasional import. Allows you buy and own machine guns of certain types, if that is your thing. Also requires you to keep records so the feds can track all purchases and sales. You cannot DEAL in firearms, if I recall without looking it up sales are limited to 6 guns a year, don't quote me here though, it's been awhile since I have read the regs. It's really good to have, especially when at a gun show and something shows up that you want to take home with you. The ATF Form 7CR is available for download at
http://www.atf.treas.gov/firearms/index.htm
on the left click on 'forms'. You will need Adobe Acrobat to get it and legal size paper to print it.