The GAU-8 itself weighs , but the complete weapon, with feed system and drum, weighs with a maximum ammunition load. It measures from the muzzle to the rearmost point of the ammunition system, and the ammunition drum alone is in diameter and long. Power for operating the gun is provided by twin
hydraulic motors pressurized from two independent hydraulic systems. The magazine can hold 1,174 rounds, although 1,150 rounds are the typical load-out. Muzzle velocity when firing armor-piercing incendiary rounds is 1,013 m/s, almost the same as the substantially lighter
M61 Vulcan's 20 mm round, giving the gun a
muzzle energy of just over 200
kilojoules. round next to a
.30-06 Springfield for comparison The standard ammunition mixture for antiarmor use is a five-to-one mix of PGU-14/B
armor-piercing incendiary, with a projectile weight around 14.0 oz (395 g or 6,096 gr) and PGU-13/B
high-explosive incendiary rounds, with a projectile weight around 13.3 oz (378 g or 5,833 gr). The PGU-14/B's projectile incorporates a lightweight aluminum body, cast around a smaller caliber
depleted uranium penetrating core. In 1979, the Avenger was tested against M47 Patton tanks and caused "severe damage". An innovation in the design of the GAU-8/A ammunition is the use of aluminum alloy cases in place of the traditional steel or brass. This rate was later changed to a fixed rate of 3,900 rpm. At this speed, 18 seconds of sustained fire are needed to empty the magazine. In practice, the cannon is limited to one- and two-second bursts to avoid overheating and conserve ammunition; barrel life is also a factor, since the USAF has specified a minimum life of at least 20,000 rounds for each set of barrels. The seven-barrel carriage assembly itself is driven by the aircraft's dual hydraulic system. The GAU-8/A ammunition feed is linkless, reducing weight and avoiding a great deal of potential for jamming. Additionally, the feed system is double-ended, allowing the spent casings to be returned to the ammunition drum and minimising any shifts on the aircraft's center of gravity. The feed system is based on that developed for later M61 installations, but uses more advanced design techniques and materials throughout, to save weight. While the GAU-8/A has a muzzle velocity comparable to that of the
M61 Vulcan, it uses heavier ammunition and has superior ballistics. The time of flight of its projectile to is 25%-30% less than that of an M61 round; the GAU-8/A projectile decelerates much less after leaving the barrel, and it drops a negligible amount, about over the distance. The GAU-8/A precision when installed in the A-10 is rated at "5
mil, 80%", meaning that 80% of rounds fired will hit within a cone with an angle of five
milliradians; this equates to a diameter circle at the weapon's design range of . By comparison, the M61 has an 8-milliradian dispersion. The GAU-8/A uses recoil adapters, which are the interface between the gun housing and the gun mount. By absorbing (in compression) the recoil forces, they spread the time of the recoil impulse and counter recoil energy transmitted to the supporting structure when the gun is fired. machine-gun crew, footage captured by overhead U.S military-operated reconnaissance drone, Afghanistan. The A-10 engines were initially susceptible to
flameout when subjected to gases generated in the firing of the gun. When the GAU-8 is being fired, the smoke from the gun can make the engines stop, and this did occur during initial flight testing. The average recoil force of the GAU-8/A is 10,000
pounds-force (45 kN), which is slightly more than the output of each of the A-10's two
Fairchild Republic TF34 engines of 9,065 lbf (40.3 kN). While this recoil force is significant, in practice, a cannon-fire burst slows the aircraft by only a few miles per hour in level flight. ==Variants==