Wal-Mart Sells Machine Guns!

[gejohnston]

60. you can in most states

but remember, it must be IAW federal law, National Firearms Act of 1934 and Title 2 of Gun Control Act of 1968. Mostly antique collectors. I met a Canadian college professor who is an expert in Nambu pistols. She got interesting in them because her dad used to collect machine guns back when Canada's laws on such weapons was laxer than ours (before 1977).
To take any item regulated under NFA-34 across state lines, you must get authorization from ATF.
http://www.atf.gov/firearms/faq/national-firearms-act-firearms.html

Speaking to Wyoming specifically, I am guessing no one saw a need to. The St Valentines Day Massacre took place in Chicago, not in Wyoming. There were no machine gun crimes there. There was no market for them in Wyoming. Second, very few if any private individuals in the US actually bought them. One was usefulness and expense (like the BAR after WW1, at $6K in today's money when the average wage would be $800/mo.) As someone else pointed out, they are quite useless outside of their narrow military function. The Thompson SMG was also very expensive and Auto Ordnance's company policy was not to sell them to the general public. The mob created dummy security companies like the Gopher Mining Corporation to purchase them.

The roving gangs in the mid-west stole theirs from national guard and police armories. One stolen by John Dillinger was returned to the police department that owned it 67 years later.

http://en.wikipedia.org/wiki/John_Dillinger

http://chestertontribune.com/PoliceFireEmergency/stolen_thompson_submachine_gun_returned.htm

Even today, most of them are registered to police departments, museums, and collectors.

Given the price of ammo and at 700 rounds per minute, Richard Pryor's character in Brewster's Millions could have used a couple at a shooting range.

http://www.imdb.com/title/tt0088850/