M134 Minigun is known as the highest firing rate machine gun in service. M134 was designed for the military purpose and was meant to be used in helicopters with shooting rate as high as 6000 rounds per minute. It fires at 10 times faster rate than an ordinary machine gun. The Guinness book of world record has featured the world highest rate of fire machine gun.
The metal storm gun, a prototype of machine gun made recently, makes M134 look like a toy. It can shoot at an alarming rate of 1 million rounds per minute. This machine gun was developed by the same name Australian based company. In 2007, Metal Storm Inc. started delivering these guns to the U.S. Navy. Following video just demonstrates the amazing gun!
One might wonder that how the lesser number of barrels offer such a great firing rate. Well, Metal Storm uses superposed projectile technology. The company owns the patent. Multiple projectiles are loaded into the barrel with propellant packed in between each one of them to give them an initial propulsion. The propellant continues to burn consecutively giving initial velocity to the packed projectiles.
Metal storm can shoot loaded projectiles in series. A seal is required which stops projectiles loaded behind the muzzle. A primer was designed for the metal storm which gives an opposite force to the projectiles loaded behind the muzzle while giving a forward push to the ones loaded at the brink of the muzzle. This allows the metal storm to fire projectiles consecutively.
Accurate to say, this technology is just amazing and there is no chance for someone to escape its shooting range.