Military pilots have no shortage of weaponry at their fingertips when flying their aircraft. But pilots who are shot down behind enemy lines are worse than a bird with clipped wings. Most pilots in the First and Second World Wars carried no more than a sidearm.

The U.S. Air Force relied on some rather odd survival weapons for pilots during the Cold War. Among the earliest such weapons was the M4 Survival Rifle, a .22 caliber bolt-action rifle developed by Harrington & Richardson from their commercial M265 sporting rifle. It featured a sheet metal frame with a telescoping wire butt stock. The M4 Survival Rifle was mainly intended to allow a downed aircrew to hunt wild game for food rather than to deal with a hostile enemy.

The M6 Aircrew Survival Weapon was another compact weapon designed with pilots in mind. Developed by the Ithaca Gun Company and the Springfield Armory as rifle/shotgun, it was issued to pilots who flew over the Arctic and other uninhabited areas. Like the M4, the M6 was better suited for foraging than defending, which prompted the Air Force to explore other options.

Next came the AR-5, a bolt action takedown rifle that was still chambered for the .22 Hornet cartridge. That led to the development of the ArmaLite AR-7 Explorer, a semi-automatic firearm in .22 Long Rifle caliber that was developed by Eugene Stoner. Stoner would go on to develop the AR-10 and AR-15. Introduced in 1959, it is still in use today as an aircrew and civilian survival weapon. While a generally reliable firearm the AR-7's biggest drawback was that it lacked stopping power.

Enter the GAU-5

The Air Force decided that pilots might need an actual weapon, though, and turned to another from Stoner’s AR-15 platform. The Air Force had already been the first branch of the service to adopt the AR-15 and soon decided to adopt a carbine version with a 10.5-inch barrel and four-inch flash hider.

Unlike the Army or Marines, the Air Force had no naming convention for small arms and simply put the weapon in its aircraft gun category. Thus was born the GAU-5/A. It became the standard issue weapon for Security Police dog handlers and other specialized personnel. GA was meant to denote an automatic gun while U was for "unit" hence: "Gun, Automatic, Unit."

The U.S. Army also adopted a nearly identical version of the weapon, which Colt – then the sole maker of the CAR-15 line of military firearms – called the XM177E1. Both versions offered select fire with semi-automatic and full-automatic fire modes, and each was officially classified by Colt as a "submachine gun." This was despite the fact that these still were chambered in the .223 Remington cartridge rather than a pistol cartridge that is typically used in submachine guns.

The GUU-5/P

The Air Force's GAU-5 was further updated as the GUU-5/P, featuring a longer 14.5-inch barrel with a 1-in-12 twist, but the firearm otherwise kept the modular design that had made the CAR-15s popular with the military.

During the Vietnam War, the Air Force also developed the Model 608 CAR-15 Survival Rifle. It was provided for use by downed aircrews for more than hunting for food. That model, which resembled the Colt Commando, actually featured a ten-inch barrel along with a modular design that allowed it to be broken down into two subassemblies and stowed in a seat pack.

More recently, the Air Force has again considered the benefits of a modular takedown weapon such as the GAU-5A. This new version is a modified M4 carbine, the same type that is currently used by the U.S. Army and United States Marine Corps, as well as Air Force security personnel. This version can break into two major pieces for storage within an aircraft including the ACES II ejection seat.

These new versions were designed by the Air Force Gunsmith Shop, which was first formed in 1958 to repair and refurbish small arms for the Air Force. The crafty airmen at the Gunsmith Shop have made numerous modifications to the M4, such as replacing the standard 14.5-inch barrel with a 12.5-inch version to help it fit in ejection seats. That is no ordinary barrel but rather the specialized Cry Havoc Tactical Quick Release Barrel (QRB) kit, which allows the gun to neatly break into two pieces.

The weapon, which weighs less than seven pounds, can be assembled in about thirty seconds. Unlike the original survival weapons that were primarily only good for foraging, the GAU-5A fires the high velocity 5.56mm round. It can take down large game but also defend against enemy soldiers who might expect to find a poorly-armed pilot.

To date the Air Force's Gunsmith Shop has built and shipped out some 2,700 of the new weapons. The cost to develop the system was around $2.6 million, which puts a price tag that is less than $1,000, or what a reasonably-priced civilian AR-15 might cost.

Peter Suciu is a Michigan-based writer who has contributed to more than four dozen magazines, newspapers and websites. He regularly writes about military small arms, and is the author of several books on military headgear including A Gallery of Military Headdress, which is available on Amazon.com.

Image: U.S. Air Force Flickr.