The U.S. military may implement a robot that has fired a machine gun at targets up to 500 feet away.

Though drones have assaulted targets from the sky, this is the first time a robot on the ground has fired a weapon. Four companies tested the gun-wielding bots in front of senior army officers at Fort Benning, Ga., last weekend.

Land robots have long been a part of the U.S. military, most notably as bomb disposers. The robot that fired the M-240 machine gun is called the Protector, and had previously only been used to clear paths, dig defensive positions and carry up to 500 pounds of equipment for infantry. It's maximum speed is only 5 miles per hour.

But with a machine gun mounted on top, "protector" takes on a different tone. Soldiers can operate the remote-control robot from a distance of up to 3,300 feet, and it can spit ammunition 5,900 feet away, according to Popular Science. HDT Global, the company that built the Protector, didn't respond to phone call and email requests for comment.

Robots are constantly becoming more commonplace in the military. Mashable recently reported that the army is building an Iron Man-like suit, and an expert told Computerworld he believes robots will soon outnumber humans in the military by 10 to one. Experts at robotics companies such as iRobot and 5D Robotics did not immediately respond to requests for comment.

The thing that separates the real proliferation of robots from sci-fi movies is autonomy. So far, the most advanced mechanical soldiers are only semi-autonomous, but experts believe that within a few decades robots could precede humans into battle. Whether or not they'll act on their own is another question.

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