# GAU-8 Avenger
The **GAU-8/A Avenger** is a 30 mm hydraulically driven seven-barrel Gatling-style autocannon built by [General Electric](https://www.edgepedia.org/general-electric) as the primary armament of the [United States Air Force](https://www.edgepedia.org/united-states-air-force)'s Fairchild Republic A-10 Thunderbolt II close air support aircraft. It fires powerful rounds at a high rate of fire, fixed in service at 3,900 rounds per minute, and was designed specifically for the anti-tank role.[1](https://www.aftc.af.mil/News/On-This-Day-in-Test-History/Article-Display-Test-History/Article/2482833/february-26-1974-live-firing-tests-of-a-30mm-gau-8-cannon-mounted-in-a-10/) • [2](https://theaviationist.com/2025/07/29/engineering-maintenance-a-10s-gau-8-a-cannon/)
| Key fact | Detail |
|---|---|
| Type | 30 mm, seven-barrel, hydraulically driven Gatling-style autocannon[1](https://www.aftc.af.mil/News/On-This-Day-in-Test-History/Article-Display-Test-History/Article/2482833/february-26-1974-live-firing-tests-of-a-30mm-gau-8-cannon-mounted-in-a-10/) |
| Rate of fire | Originally selectable 2,100 or 4,200 rounds per minute; later fixed at 3,900 rounds per minute[2](https://theaviationist.com/2025/07/29/engineering-maintenance-a-10s-gau-8-a-cannon/) • [3](https://media.defense.gov/2010/Sep/27/2001329817/-1/-1/0/gulf_war_air_power_survey-vol4.pdf) |
| Size and weight | Gun 105 inches long, 641.5 pounds; complete system with loaded drum 3,818.3 pounds; with drum and 1,350 rounds the installed weapon weighed nearly two tons and was 20 ft long[4](https://d34w7g4gy10iej.cloudfront.net/pubs/pdf_76536.pdf) • [1](https://www.aftc.af.mil/News/On-This-Day-in-Test-History/Article-Display-Test-History/Article/2482833/february-26-1974-live-firing-tests-of-a-30mm-gau-8-cannon-mounted-in-a-10/) |
| Ammunition capacity | Prototype drum 1,200 rounds, total system 1,386; Gulf War magazine held 1,350 rounds[4](https://d34w7g4gy10iej.cloudfront.net/pubs/pdf_76536.pdf) • [3](https://media.defense.gov/2010/Sep/27/2001329817/-1/-1/0/gulf_war_air_power_survey-vol4.pdf) |
| Feed system | Linkless, double-ended; empty aluminum cases are returned to the drum instead of ejected[4](https://d34w7g4gy10iej.cloudfront.net/pubs/pdf_76536.pdf) • [2](https://theaviationist.com/2025/07/29/engineering-maintenance-a-10s-gau-8-a-cannon/) |
| Barrel life | 14,000 rounds per set of seven barrels[4](https://d34w7g4gy10iej.cloudfront.net/pubs/pdf_76536.pdf) |
| Main anti-armor round | PGU-14/B API with a depleted-uranium penetrator; Air Force fired 783,514 API rounds (about 259 tons of DU) in the Gulf War[5](https://gulflink.osd.mil/du_ii/du_ii_tabf.htm) |
## Development
The Air Force began examining requirements in the 1960s for a close air support aircraft built around a large-bore rapid-fire cannon, and in September 1969 its Close Air Support Gun System Study Group recommended a 30 mm internally mounted [Gatling gun](https://www.edgepedia.org/gatling-gun) with a family of associated rounds developed especially for the mission.[4](https://d34w7g4gy10iej.cloudfront.net/pubs/pdf_76536.pdf) On November 16, 1970 the Air Force issued a request for proposal for a 30 mm rapid-fire cannon for the A-X close air support aircraft, and in June 1971 it awarded letter contracts to General Electric and Philco-Ford for competitive development of the gun system and four types of ammunition: Target Practice, High Explosive Incendiary, Semi-Armor Piercing High Explosive, and Armor Piercing Incendiary.[6](https://www.nationalmuseum.af.mil/Visit/Museum-Exhibits/Fact-Sheets/Display/Article/196738/gau-8a-avenger/) • [4](https://d34w7g4gy10iej.cloudfront.net/pubs/pdf_76536.pdf) The contracted specifications required the gun to destroy light, medium, and heavy tanks, armored personnel carriers, fixed or mobile artillery, and hardened targets such as bunkers and equipment within revetments.[6](https://www.nationalmuseum.af.mil/Visit/Museum-Exhibits/Fact-Sheets/Display/Article/196738/gau-8a-avenger/)
**Competitors and backup.** The Air Force also contracted with the Hughes Tool Company for a backup system, the Swiss-made Oerlikon 304RF-30 designated GAU-9. Testing completed in April 1973 proved the GAU-9 inferior to the GAU-8, and it was dropped from the competition.[4](https://d34w7g4gy10iej.cloudfront.net/pubs/pdf_76536.pdf) The Air Force evaluated the General Electric and Philco-Ford prototypes in firing tests at Eglin AFB, Florida, from January 3 to April 6, 1973, and declared General Electric the winner.[4](https://d34w7g4gy10iej.cloudfront.net/pubs/pdf_76536.pdf) On June 21, 1973 the full-scale development contract for the GAU-8/A gun system was awarded to General Electric as a fixed-price-incentive contract of $23,754,567 for three preproduction systems.[4](https://d34w7g4gy10iej.cloudfront.net/pubs/pdf_76536.pdf)
The gun was not ready for the A-X fly-off between the Northrop A-9A and Republic A-10A, so the General Electric M61A1 "Vulcan" 20 mm cannon was installed for initial weapons testing of the two aircraft.[6](https://www.nationalmuseum.af.mil/Visit/Museum-Exhibits/Fact-Sheets/Display/Article/196738/gau-8a-avenger/) The gun's importance to the aircraft was confirmed during the later A-7D/A-10 controversy: without the big cannon the A-10 was neither cost-effective nor technologically superior against heavy targets, and in the Saber Compare fly-off of April and May 1974 the GAU-8/A destroyed tanks at a single-pass probability of kill of 0.21 while the A-7D's M61 was virtually useless against hard targets.[4](https://d34w7g4gy10iej.cloudfront.net/pubs/pdf_76536.pdf)
## Design
The gun follows Richard Gatling's original principles: seven barrels, each with its own breech and bolt, rotate as a single unit within an outer housing, and only one barrel fires at a time. Two hydraulic motors drive the rotation; originally running only one motor slowed the rate from 4,200 to about 2,100 rounds per minute, but the rate was later fixed at 3,900.[2](https://theaviationist.com/2025/07/29/engineering-maintenance-a-10s-gau-8-a-cannon/) The firing barrel sits on the aircraft's exact centerline, directing reaction forces through the airplane's center of gravity, and the A-10 and its gun were treated as an integrated weapon system rather than an aircraft to which a gun was added.[7](https://www.airandspaceforces.com/app/uploads/2024/09/AFmag_1973_12.pdf)
The ammunition system is a linkless, double-ended feed: one path carries rounds from the drum to the gun, and the other returns empty aluminum cases to the drum instead of ejecting them from the aircraft.[4](https://d34w7g4gy10iej.cloudfront.net/pubs/pdf_76536.pdf) • [2](https://theaviationist.com/2025/07/29/engineering-maintenance-a-10s-gau-8-a-cannon/) The muzzle velocity is about the same as that of the [M61 Vulcan](https://www.edgepedia.org/m61-vulcan), but the GAU-8/A fires heavier ammunition with superior ballistics; the M61 has an 8-milliradian dispersion.[1](https://www.aftc.af.mil/News/On-This-Day-in-Test-History/Article-Display-Test-History/Article/2482833/february-26-1974-live-firing-tests-of-a-30mm-gau-8-cannon-mounted-in-a-10/) At a slant range of 4,000 feet, the GAU-8 round carries 14 times the kinetic energy of a 20 mm projectile fired from the M61 Vulcan.[3](https://media.defense.gov/2010/Sep/27/2001329817/-1/-1/0/gulf_war_air_power_survey-vol4.pdf)
## Flight testing problems
Live firing of the gun installed in an A-10 began on February 26, 1974 at Edwards AFB, with the objective of determining gun and aircraft compatibility.[1](https://www.aftc.af.mil/News/On-This-Day-in-Test-History/Article-Display-Test-History/Article/2482833/february-26-1974-live-firing-tests-of-a-30mm-gau-8-cannon-mounted-in-a-10/) On March 11, 1974 a long burst ignited a fireball of gun gases just forward of the nose, and a second test that day caused airflow disturbances and mild compressor stalls in the engines, the first indication of a stubborn gun gas problem tied to the weapon's high rate of fire.[8](https://www.aftc.af.mil/About-Us/History/On-This-Day-in-Test-History/Article-Display-Test-History/Article/2501024/march-11-1974-a-10-stubborn-gun-gas-gau-8-rotary-gun-testing/)
**Three problems, three fixes.** Secondary gun gas ignition, which produced a flame area ahead of the nose and perturbed engine internal pressure, was traced largely to differences in propellant between test phases; the solution was to modify the propellant formulation, adding potassium salts as a suppressant, and the problem was declared closed on November 7, 1974.[4](https://d34w7g4gy10iej.cloudfront.net/pubs/pdf_76536.pdf) Gun gas residue on the windscreen impaired pilot vision and degraded engine thrust; a windshield washer system and washing the engine with water proved operationally acceptable, since the residue, potassium bicarbonate, was water soluble.[4](https://d34w7g4gy10iej.cloudfront.net/pubs/pdf_76536.pdf) A 1976 GAO report also recorded that unburned propellant residue accumulating on the aircraft was highly corrosive to aluminum and reduced visibility and thrust during gun-firing missions, with a propellant change seen as the long-term solution.[9](https://www.gao.gov/assets/lcd-76-449.pdf) Finally, the gun angle was wrong for low dive-angle strafing; flight tests in June 1974 showed a two-degree downward gun alignment was best, and the A-10 was modified accordingly.[4](https://d34w7g4gy10iej.cloudfront.net/pubs/pdf_76536.pdf)
## Ammunition
The 30 mm family included HEI, effective against trucks, personnel, and soft or semi-hard targets; SAPHE, later dropped as too complex and costly for its marginal effectiveness; and API rounds. Steel-penetrator API achieved its penetration goals but lacked sufficient effectiveness against tanks and was eliminated, so development concentrated on high-density penetrators, preferably depleted uranium.[4](https://d34w7g4gy10iej.cloudfront.net/pubs/pdf_76536.pdf) Phase I tests yielded 2.35 inches of penetration of rolled homogeneous armor at 30 degrees obliquity with DU penetrators, and the Air Force proposed a penetrator of DU alloyed with 0.75 percent titanium.[4](https://d34w7g4gy10iej.cloudfront.net/pubs/pdf_76536.pdf) The resulting PGU-14/B API round has a lightweight body containing a sub-caliber high-density penetrator of depleted uranium.[10](https://www.111attackwing.ang.af.mil/Portals/11/documents/Archived-Newsletters/AFD-120208-026.pdf)
## Combat use
The [Gulf War](https://www.edgepedia.org/gulf-war) was the first conflict with extensive use of DU munitions. The 148 A-10s that deployed to Saudi Arabia flew 8,077 combat sorties, and a typical combat load included about 1,100 rounds of 30 mm ammunition. API and HEI rounds are mixed at the factory in a 5-to-1 ratio as Combat Mix Ammunition, and the Air Force fired 783,514 rounds of 30 mm API, expending about 259 tons of depleted uranium.[5](https://gulflink.osd.mil/du_ii/du_ii_tabf.htm) The Gulf War Air Power Survey records that A-10s fired almost a million rounds of 30 mm ammunition against all types of targets, especially armor and trucks.[3](https://media.defense.gov/2010/Sep/27/2001329817/-1/-1/0/gulf_war_air_power_survey-vol4.pdf) The gun's performance in the Gulf War solidified the A-10's reputation as an armor destroyer, and A-10s were called on again against armored targets in the Balkans.[11](https://www.nato.int/en/news-and-events/events/transcripts/2001/01/10/briefing)
## References
1. [February 26, 1974: Live Firing Tests of a 30mm GAU-8 Cannon Mounted in A-10, Air Force Test Center](https://www.aftc.af.mil/News/On-This-Day-in-Test-History/Article-Display-Test-History/Article/2482833/february-26-1974-live-firing-tests-of-a-30mm-gau-8-cannon-mounted-in-a-10/)
2. [A Look at the Engineering and Maintenance of the A-10's GAU-8/A Cannon, The Aviationist](https://theaviationist.com/2025/07/29/engineering-maintenance-a-10s-gau-8-a-cannon/)
3. [Gulf War Air Power Survey, Volume IV: Weapons, Tactics, and Training](https://media.defense.gov/2010/Sep/27/2001329817/-1/-1/0/gulf_war_air_power_survey-vol4.pdf)
4. [Birth of a Hog: Beginnings of the A-10 Warthog](https://d34w7g4gy10iej.cloudfront.net/pubs/pdf_76536.pdf)
5. [TAB F: DU Use in the Gulf War, Operation Desert Storm DU exposure report](https://gulflink.osd.mil/du_ii/du_ii_tabf.htm)
6. [GAU-8/A Avenger, National Museum of the United States Air Force](https://www.nationalmuseum.af.mil/Visit/Museum-Exhibits/Fact-Sheets/Display/Article/196738/gau-8a-avenger/)
7. [Air Force Magazine, December 1973](https://www.airandspaceforces.com/app/uploads/2024/09/AFmag_1973_12.pdf)
8. [March 11, 1974: A-10 Stubborn Gun Gas GAU-8 Rotary Gun Testing, Air Force Test Center](https://www.aftc.af.mil/About-Us/History/On-This-Day-in-Test-History/Article-Display-Test-History/Article/2501024/march-11-1974-a-10-stubborn-gun-gas-gau-8-rotary-gun-testing/)
9. [LCD-76-449: Programs for Procuring Conventional Ammunition, U.S. GAO](https://www.gao.gov/assets/lcd-76-449.pdf)
10. [1212S, 111th Attack Wing newsletter](https://www.111attackwing.ang.af.mil/Portals/11/documents/Archived-Newsletters/AFD-120208-026.pdf)
11. [NATO briefing transcript, 2001](https://www.nato.int/en/news-and-events/events/transcripts/2001/01/10/briefing)
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*Topic: Encyclopedia › Technology and the built world › Engineering and manufacturing › Artillery*
*Initially written Sep 17, 2026 · Reviewed: Sep 17, 2026; Oct 15, 2026 · Edited: Oct 15, 2026 · Last review: Oct 15, 2026*
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