Can Some gun expert answer this question about AR-15......

[99th_Monkey]

6. MoJo: Everything you need to know re: AR-15 "easy conversion" to FULL automatic

In 1986, it became illegal for civilians to own newly made machine guns. But with just $299, you can modify your semi-automatic AK-47 or AR-15:

Slide Fire is a company that sells gun stocks that you can use with an AK-47 or an AR-15. These attachments enable accurate "controlled rapid firing," according to the company's website, meaning "you can shoot one round, 2 rounds…15 rounds or a full magazine," as Jeremiah Cottle, the US Air Force vet who invented the product, told Guns America last year.

Gun enthusiasts, who have posted videos on YouTube of the Slide Fire in use, seem to love the product. "It's just like an M-16!" the shooter in the YouTube video above exclaims. "You can shoot it accurately…or if you want to have fun, you can just spray the shit out of everything." Survivalists also love the product. "If the gun-grabbers and Brady camp gets hold of this, it's game over," wrote a user on a survivalist message board, referring to the Brady Campaign to Stop Gun Violence.

A gun modified with Slide Fire "fires as a machine gun would," explains David Coulson, a spokesman for the Bureau of Alcohol, Tobacco, Firearms, and Explosives, the federal government's gun regulator—but, he adds, that doesn't make it a machine gun.

http://www.motherjones.com/politics/2012/12/how-make-your-gun-shoot-fully-automatic-one-easy-step