Under federal law, it's illegal to alter your gun to make it fully automatic but Denver7 has learned there are devices available for sale online that do nearly the same thing and they're perfectly legal.

Slide Fire is one company that makes after-market accessories for an AR-15 and an AK-47. For $299, gun enthusiasts can purchase the device that according to the company's website, "lets shooters safely and accurately bump fire their rifles without compromising safety and accuracy."

Slide Fire accessories are not shown in the photo above.

"Those devices use the recoil of the gun, the movement of the gun... to cause the gun to fire quicker, fire faster," said Bart Miller of the Centennial Gun Club.

In 1986, the Feds made it illegal for citizens to buy and own newly made machine guns. Since then, companies have come up with devices like the Slide Fire to give shooters a similar sensation to shooting a fully automatic gun. YouTube video shows gun enthusiasts spraying bullets into the woods and exclaiming, "that's fun!" and following up with "and it's 100% legal!"

"They're fun to go out and play with but for like any real applications, they're useless. They just put your accuracy into the dirt," said gun enthusiast Alex Esley.

In 2010, The Bureau of Alcohol, Tobacco, Firearms, and Explosives, the federal government's gun regulator, evaluated the "bump fire" devices. Although they make a gun fire more rapidly, the ATF determined the firearm part is legal because it doesn't "mechanically alter the function of the gun." The ATF said in a letter the stock has "no automatically functioning mechanical parts or springs and performs no automatic mechanical function when installed."

Bart Miller of the Centennial Gun Club cautioned people from using the devices. He said it makes the gun fire faster but also makes it harder to control.

"Typically that's not a product that we handle and we don't install. Anything that affects the accuracy, the safety of the operation of the gun, we frown on, we just have decided not to work on these types of accessories," Miller said.

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