Pretty sure you CAN buy a fully auto AK-47...if you have enough money and want to fill out all the paperwork.
Last summer I was here...
http://www.bing.com/videos/search?q=oklahoma+full+auto+shoot+2012&qpvt=oklahoma+full+auto+shoot+2012&FORM=VDRE
And shot a bunch of fully auto machine guns/pistols...Was GREAT fun!!
If you pass the Class III paperwork and pay.