Further Info: http://www.westernfirearms.com/
Other than what is mentioned above, the only difference between purchasing a Class III weapon and a normal firearms purchase is that full-auto weapons are registered with the ATF.
The only factor that "regulates" their common purchase is the price (due to the statute passed back in '86 that stopped importation and civilian sales of new weapons), due to that event there now is a very limited supply of these weapons manufactured before the statute in the US, prices now start at about $15,000 and go up from there (fortunately I aquired mine before that limitation, when they were dirt cheap, nobody wanted to buy them).
According to the ATF there are about 250,000 (legally owned) "machine guns" in civilian ownership in the US, which comprises about half of the total (law enforcement owns the remainder)...........of all of these only ONE was ever used in a crime, which was committed by a police officer:
Lord only knows how many WW I "war trophys", and Thompsons, etal are sitting in attics, garages, basements and barns around the country that were legally aquired before the 1934 Act......estimates run into 500,000 or more, and they pop up in the underground market all the time. Thompson alone sold more than 25,000 to civilians.Since 1934, only one legally owned machinegun (of some 200,000+) has ever been used in crime, and that was a murder committed by a law enforcement officer. On September 15th, 1988, a 13-year veteran of the Dayton, OH police department, Patrolman Roger Waller, then 32, used his fully automatic MAC-11,.380 cal. submachinegun to kill a police informant, 52-year-old Lawrence Hileman. Patrolman Waller pleaded guilty in 1990, and he and an accomplice were sentenced to 18 years in prison. The 1986 'ban' on sales of new machineguns does not apply to purchases by law enforcement or government agencies. ---
Thanks to the staff of the Columbus, OH Public Library for the details of the Waller case.
I haven't even touched on the subject of the "DIAS" (Drop-in auto sear), which is a very small, simple device that can be installed in the fire-control group of most any semi-automatic rifle to convert it to full-auto. Criminals use these frequently, because they can be manufactured in any machine shop, for pennies........these are the preferred venue of the Mexican drug cartels, etc.
That's enough to make one hell of a "well-regulated" militia..........
Let's face facts......America is awash with guns, and any politician that thinks that they (or their political party) is going to magically get rid of them all, is "whistling past the graveyard"........it simply isn't ever going to happen.....