Here at Firearms Talk we generally talk about small arms, and small arms accessories. However let’s take a break and check out some extremely heavy firepower-- the GAU-8 Avenger cannon.
Since the US Army took an experimental Lewis machinegun up on a canvas and bamboo biplane in 1912, there has been a move to arm aircraft. After those tests in which an officer asked, "Why would anyone want to put a gun on an airplane?" ordnance has gotten bigger and more effective.
The Fulda Gap
The US military spent most of the time period between 1948 and 1989 obsessed with a plain in central Germany known as the Fulda Gap. The Fulda Gap was the most obvious route for a hypothetical Soviet tank attack upon West Germany (and NATO) from Eastern Europe. It was envisioned that thousands of Soviet and Warsaw Pact tanks would swarm into the Fulda. If the US could stop them there, World War III could be won. If not, we'd all be speaking Russian today.
With as many as 50,000 Soviet T-series tanks available to throw into the battle, the West needed an Avenger to even things out.
The GAU-8 Avenger Cannon
In 1970, the US Air Force issued a request for a giant electrically fed 7-barrel Gatling-type auto cannon. Chambered for a huge 30x173mm armor-piercing round capable of defeating Soviet armor, the GAU-8 cannon was to be used for the next USAF attack plane. The gun system by itself 'only' weighed 619-pounds. However its assembly, which includes the twin 77-hp electric motors that feed the ammunition through feet of linkless chutes, 1174 1.53 pound 30mm PGU-13/14 shells and the casing that holds it all together, the whole thing is 19-feet long and weighs over two tons. This is the same curb weight as a 2012 Chrysler 300 4-door sedan.
Designed around the cannon was the YA-10 and the YA-9 prototype planes and after a head to head trials, the YA-10, now world-famous as the A-10 Warthog was born.
The A-10 had to mount the cannon slightly off center so that when it fired, the 5-tons of recoil from the Avenger cannon would not throw the plane into a spin. Special igniters had to be installed in the twin engines of the A-10 because the gas of the spent shells, lacking oxygen, tends to flame them out when the gun fires. To keep the huge 7-inch long spent shell casings from being sucked into the engines fans and crashing the plane, the ammunition chute system feeds them back into the ammunition drum. (Note- anyone who says they picked up 30mm shell casings that fell on them after an A-10 pass is full of crap)
The only bad news is that the A-10 only carries enough ammo to fire the gun for about 16.8 seconds. To enable the Warthog to drop it like it’s hot and get out of Dodge before the Russkis could open up with the kitchen sink on it, the Avenger cannon can fire as fast as 4200-rounds per minute.
The effects of the 30mm Ammunition
The PGU-13/14 shells fired by the GAU-8 Avenger are like the hand of God. Capable of penetrating almost three inches of rolled hardened steel armor, they can knock out most modern tanks. The A-10 fires into the soft vulnerable top armor of the tank, where it is weakest. Top armor in most tanks is 50-75mm thick on the turret, less on engine deck and hatches. When you realize that the A-10, even flying at over 300knots can pepper a 10-foot square area with 20 PGU-13/14 shells in the blink of an eye, you can imagine the devastation. In terms of power, each 30mm round fired produces about 125,699 ft.-pounds of energy on impact. For a comparison, a 5.56mm FMJBT round produces 1,238.
The 30mm round compared to a 5.56mm...
Here is a video of the Avenger at work on a ground target in the Sandbox somewhere....
Aren’t you glad it’s on our side?