Full auto is already highly regulated btw, I'm not sure on the specific guidelines involving them because its too cost prohibitive for me anyway. The ironically named FOPA act of 1986 (look it up) cut off sales of any machine guns made after that point to civilians, so there is a limited pool of them out there and therefore are extremely expensive (cheapest being 3 - 5K for some MAC 10 or 11 piece of shit)
As a frame of reference the protocol for getting a suppressor or an SBR would be to - go to the store, pick it out, pay for it, gun shop owner takes it into the back and locks it away, fill out paperwork along with $200 and mail it to the ATF, wait 6 (?) months for your tax stamp, go back to the store and take it home. Congratulations its now yours forever (literally, you can never sell it or even loan it to a friend).