It’s legal to own a minigun in the US

The M134 General Electric Minigun is one of the most deadly infantry weapons ever designed. It has the capacity to fire up to one hundred and sixty six bullets per second.
 
While theoretically you could run out and buy one, there are some problems:

• First, there are only around a dozen miniguns available for civilian purchasing in the US, and only appear on the market occasionally.

• Second, and probably most obvious, is price. Whenever a minigun goes up on the market, it usually sells for around $400,000

• Third is the mounting system you have to buy separately. Despite what some hardcore action movies would have you believe, firing one of these by hand without any mounting would lead to major injury from the recoil.

• Fourth is the added cost of bullets. It’s about sixty dollars to fire the minigun for one second.

Of course there isn’t much practical use for such a weapon, even in a zombie apocalypse scenario. The reason they’re legal today is because in 1986 a law was passed that any fully automatic weapon constructed before then was legal to own. That included the miniguns already on the market.