http://www.gunbroker.com/Auction/ViewItem.aspx?Item=269948678 There's the one Watson was mentioning...
And it really is a fairly straightforward process...
1. Can you own a gun? If yes, proceed to 2, if not, you're not getting one legally.
2. Can you own the machine gun you want legally in your location? If not, stop here.
3. Find one for sale.
4. Acquire money for the one you found for sale.
5. Enter agreement to purchase.
6. Fill out the form 4 transfer paperwork with CLEO signoff or trust information.
7. Submit the form, with the fee.
8. Wait.
9. Wait.
10. Wait.
11. Get your tax stamp.
12. Get your gun.
13. Celebrate by shooting half the guns cost in ammo.
Really, it's steps 1, 2, and 4 that trip most people up depending on the gun.