GAU - 8 Avenger The General Electric GAU - 8 / A Avenger is a 30 mm hydraulically driven seven - barrel Gatling - type cannon that is typically mounted to the United States Air Force ' s Fairchild Republic A - 10 Thunderbolt II . Designed specifically for the anti - tank role , the Avenger delivers very powerful rounds at a high rate of fire . The GAU - 8 / A is also mounted to the Goalkeeper CIWS . History . The GAU - 8 was created as a parallel program with the " A - X " ( or Attack Experimental ) competition that produced the A - 10 . The specification for the cannon was laid out in 1970 , with General Electric and Philco - Ford offering competing designs . Both of the A - X prototypes , the YA - 10 and the Northrop YA - 9 , were designed to incorporate the weapon , although it was not available during the initial competition , and the M61 Vulcan was used as a temporary replacement . Once completed , the entire GAU - 8 assembly ( correctly referred to as the A / A 49E - 6 Gun System ) represents about 16 % of the A - 10 aircraft ' s unladen weight . Because the gun plays a significant role in maintaining the A - 10 ' s balance and center of gravity , a jack must be installed beneath the tail of the plane whenever the gun is removed for inspection in order to prevent the aircraft from tipping rearwards . The gun is placed slightly off center in the nose of the plane with the front landing gear positioned to the right of the center line , so that the actively firing cannon barrel is directly on the aircraft ' s center line . The Russian Gryazev - Shipunov GSh - 6 - 30 is a similar class of weapon , although it is lighter with a higher fire rate , but has a lower muzzle velocity and overheats faster . The A - 10 and its GAU - 8 / A gun entered service in 1977 . It was produced by General Electric , though General Dynamics Armament and Technical Products has been responsible for production and support since 1997 when the division was sold by Lockheed Martin to General Dynamics . The gun is loaded using Syn - Tech ' s linked tube carrier GFU - 8 / E 30 mm Ammunition Loading Assembly cart . This vehicle is unique to the A - 10 and the GAU - 8 . Design . 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 is the typical load - out . Muzzle velocity when firing Armor - Piercing Incendiary rounds is , almost the same as the substantially lighter M61 Vulcan ' s 20 mm round . The standard ammunition mixture for anti - armor use is a four - to - one mix of PGU - 14 / B Armor Piercing Incendiary , with a projectile weight of about 15 . 0 oz ( 425 grams or 6 , 560 grains ) and PGU - 13 / B High Explosive Incendiary ( HEI ) rounds , with a projectile weight of about 12 . 7 oz ( 360 grams or 5 , 556 . 25 grains ) . The PGU - 14 / B ' s projectile incorporates a lightweight aluminum body , cast around a smaller caliber depleted uranium penetrating core . The Avenger is lethal against tanks and all other armored vehicles . A very important innovation in the design of the GAU - 8 / A shells is the use of aluminum alloy cases in place of the traditional steel or brass . This alone adds 30 % to ammunition capacity for a given weight . The shells also have plastic driving band s to improve barrel life . They are imposing to examine and handle , measuring in length and weighing or more . The Avenger ' s rate of fire was originally selectable , 2 , 100 rounds per minute ( rpm ) in the low setting , or 4 , 200 rpm in the high setting . Later this was changed to a fixed rate of 3 , 900 rpm . 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 . There is no technical limitation on the duration the gun may be continuously fired , and a pilot could potentially expend the entire ammunition load in a single burst with no damage or ill effects to the weapons system itself . However , this constant rate of fire would shorten the barrel life considerably and require added barrel inspections and result in shorter intervals between replacement . Each barrel is a very simple non - automatic design having its own breech and bolt . Like the original Gatling gun , the entire firing cycle is actuated by cam s and powered by the rotation of the barrels . The barrels themselves are driven by the aircraft ' s dual hydraulic system . The GAU - 8 / A ammunition is linkless , reducing weight and avoiding a great deal of potential for jamming . The feed system is double - ended , allowing the spent casings to be recycled back into the ammunition drum , instead of ejected from the aircraft , which would require considerable force to eliminate potential airframe damage . The feed system is based on that developed for later M61 installations , but uses more advanced design techniques and materials throughout , to save weight . Firing system . Accuracy . The GAU - 8 / A is extremely accurate and can fire 4 , 200 rounds per minute without complications . The 30 - mm shell has twice the range , half the time to target , and three times the mass of projectiles carried by comparable Close Air Support aircraft . The muzzle velocity of the GAU - 8 / A is about the same as that of the M61 Vulcan cannon , but uses heavier ammunition and has superior ballistics . Its time of flight to is 30 percent less than that of an M61 round , the projectile decelerates much less rapidly after leaving the barrel , and it drops a negligible amount , about over the distance . The GAU - 8 / A accuracy when installed in the A - 10 is rated at " 5 mil , 80 percent " , meaning that 80 percent 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 . Recoil . Each barrel fires when it reaches roughly the 9 o ' clock position , when viewed from the front of the plane . Because the gun ' s recoil forces could push the entire plane off target during firing , the weapon itself is mounted off - center in the other direction , toward the 3 o ' clock position , so that the firing barrel lies directly on the aircraft ' s center line . The firing barrel also lies just below the aircraft ' s center of gravity , being bore sighted along a line 2 degrees below the aircraft ' s line of flight . This arrangement accurately centers the recoil forces , preventing changes in pitch and / or yaw when fired . This configuration also provides space for the front landing gear , which is mounted slightly off - center on the right side of the nose . The GAU - 8 / A utilizes recoil adapters . They 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 . 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 . Gun exhaust is essentially oxygen - free , and is certainly capable of causing flame - outs of gas turbines . The A - 10 engines now have a self - sustaining combustion section . When the gun is fired the igniters come on to reduce the possibility of a flame - out . The recoil force of the GAU - 8 / A is 10 , 000 pounds - force ( 45 kN ) , which is slightly more than the output of one of the A - 10 ' s two TF34 engines ( 9 , 065 lbf / 40 . 3 kN each ) . While this recoil force is significant , in practice cannon fire only slows the aircraft a few miles per hour . Variants . Some of the GAU - 8 / A technology has been transferred into the smaller 25 mm GAU - 12 / U Equalizer developed for the AV - 8B Harrier II aircraft , which is about the same size as the M61 , but is considerably more lethal . GE has also developed the GAU - 13 / A , a four - barreled weapon using GAU - 8 / A components , which has been tested in podded form as the GPU - 5 / A , and the Avenger forms the basis for the Dutch - developed Goalkeeper CIWS naval air - defence gun . No current or contemplated aircraft other than the A - 10 , however , carries the full - up Avenger system . See also . Non - NATO : General :