The nose of an A-10 Thunderbolt II showing the GAU-8 Avenger muzzle and shark mouth markings

The GAU-8 Avenger: The Cannon They Built a Plane Around

by Max Grünwald | Sep 23, 2026 | Mundo de la aviación, Aviación militar | 0 comments

You have heard the claim. The A-10’s gun is so powerful that firing it stops the aeroplane in mid-air.

It does not. A burst costs the aircraft a few miles an hour in level flight. But the claim keeps circulating because the real numbers are almost as ridiculous, and because the A-10 Thunderbolt II genuinely was designed around this object rather than the other way round.

The gun specification was written in 1970, alongside the A-X competition that produced the aircraft. Both prototypes, the YA-10 and the Northrop YA-9, were designed to carry a cannon that did not yet exist; they flew the competition with an M61 Vulcan as a stand-in.

Datos rápidos

Arma	General Electric GAU-8/A Avenger, 30 mm seven-barrel rotary cannon
Complete assembly	A/A 49E-6 Gun System — about 16% of the A-10’s empty weight
Specification written	1970, in parallel with the A-X competition
En servicio	Since 1977
Rate of fire	3,900 rounds per minute
Ammunition	1,150 rounds typical; five PGU-14/B armour-piercing incendiary to one PGU-13/B high-explosive incendiary
Recoil	10,000 lbf, slightly more than the thrust of one TF34 engine
Also used by	The Dutch Goalkeeper close-in weapon system on warships

Sixteen per cent of an aeroplane

The complete installation — properly the A/A 49E-6 Gun System — runs from the muzzle to the back of the ammunition drum, nearly six metres, and accounts for about sixteen per cent of the A-10’s empty weight.

Which produces one of the better pieces of trivia in military aviation: when the gun is removed for inspection, a jack has to be placed under the tail, or the aeroplane sits down on its arse.

A GAU-8 Avenger seven-barrel 30 mm cannon on display — The gun itself weighs 620 lb. With the feed system and a full drum, the installed weapon weighs 4,029 lb. Photo: Wikimedia Commons

The off-centre trick

Look at an A-10 from the front and something is slightly wrong. The nose gear is off to the right. The gun is off to the left.

That is deliberate and it is elegant. Only one of the seven barrels fires at a time — the one at the nine o’clock position — so the whole gun is offset to port in order to put the firing barrel exactly on the aircraft’s centreline, just below the centre of gravity, bore-sighted two degrees below the line of flight. The recoil therefore acts straight down the aircraft’s axis and produces no pitch or yaw. The nose gear got moved out of the way.

The animation that has been watched ten million times, and the clearest explanation of the mechanism available.

Two seconds

At 3,900 rounds per minute, a full drum lasts about eighteen seconds. Nobody fires it that way. Bursts are one to two seconds, partly to conserve ammunition and partly because the Air Force wants at least 20,000 rounds of life out of each set of barrels.

“The thing shook the airplane when you pulled the trigger. You could smell the spent casings even with the oxygen mask on. The sound is muffled with all the gear we wear, but you still hear it. The high rate of fire and typical range mean the rounds hit just before or about the time you release the trigger.”

John Marks — A-10 pilot, on firing the GAU-8 in the Gulf War, interviewed by Smithsonian Magazine

The round matters as much as the rate. It is 30 x 173 mm, loaded five armour-piercing incendiary to one high-explosive incendiary. The PGU-14/B armour-piercing round is a depleted uranium penetrator cast inside a lightweight aluminium body, and the cases themselves are aluminium alloy rather than steel or brass, which buys about thirty per cent more ammunition for the same weight.

An OA-10 Thunderbolt II firing its GAU-8/A Avenger 30 mm cannon at a target range — A burst on the range. The projectile drops about ten feet over 4,000 feet and gets there roughly a quarter faster than a 20 mm round from an M61. Photo: US Air Force

“Eighty per cent of rounds fired at 4,000 feet range hit within a 40-foot diameter circle.”

US Air Force GAU-8/A specification — Published accuracy standard, quoted by Hill Air Force Base and the Federation of American Scientists

The problem nobody expected

Early flight testing turned up something the designers had not planned for: firing the gun stopped the engines.

Gun gas is essentially oxygen-free, and an A-10 firing forward flies straight into its own exhaust. The engines flamed out. The fix was a self-sustaining combustion section and an arrangement whereby the igniters come on automatically whenever the trigger is pulled — which is to say the A-10 relights its engines every time it shoots.

Why nobody else carries it

In November 1988 the Air Force tried. The 174th Tactical Fighter Wing gave up its A-10s for F-16A/Bs and carried the four-barrel GAU-13/A in a GPU-5/A Pave Claw pod into Desert Storm, as the F/A-16.

It did not work. A pylon-mounted pod is less rigid than a gun bolted into an airframe, so vibration ruined the accuracy; there was no continuously computed impact point software; and the F-16 arrives faster, giving the pilot less time to aim. The gun was found ineffective against point targets and worse than cluster munitions against area targets. The idea was dropped quickly.

The technology went elsewhere instead. A 25 mm derivative, the GAU-12/U Equalizer, arms the AV-8B Harrier II. And the full Avenger sits on warships as the Dutch Goalkeeper close-in weapon system, where the target is an incoming missile rather than a tank.

No aircraft other than the A-10 has ever carried the complete gun. As the Warthog leaves service, that will simply stop being a thing aeroplanes do.

Sources: National Museum of the United States Air Force; Hill Air Force Base factsheet; Federation of American Scientists; General Dynamics Ordnance and Tactical Systems; Dennis R. Jenkins, Fairchild-Republic A/OA-10 Warthog; Michael Spick, The Great Book of Modern Warplanes; Smithsonian Magazine; Naval Postgraduate School combat damage assessment, 1980.

Preguntas frecuentes

Was the A-10 built around the GAU-8?

Effectively, yes. The cannon specification was written in 1970 in parallel with the A-X competition that produced the aircraft, and both prototypes were designed to carry it. The complete gun system accounts for about 16 per cent of the A-10’s empty weight.

How fast does the GAU-8 fire?

3,900 rounds per minute. The rate was originally selectable between 2,100 and 4,200 rounds per minute and was later fixed. At that rate a full magazine of about 1,150 rounds would be gone in roughly 18 seconds of continuous fire.

Does firing the GAU-8 slow the A-10 down?

A little, but not dramatically. The average recoil force is about 10,000 pounds, slightly more than the thrust of one of the aircraft’s two TF34 engines, and a burst slows the aircraft by a few miles per hour in level flight. The popular claim that it stops the aeroplane is wrong.

Why is the gun mounted off-centre on the A-10?

So that the barrel actually firing sits on the aircraft centreline. The seven barrels rotate, and only the one at the nine o’clock position fires. Offsetting the whole gun to port puts the firing barrel on the centreline, which keeps the recoil from pitching or yawing the aircraft.

What ammunition does the GAU-8 fire?

A 30 x 173 mm round, normally loaded five to one: PGU-14/B armour-piercing incendiary with a depleted uranium core in an aluminium body, and PGU-13/B high-explosive incendiary. The cases are aluminium alloy rather than steel or brass, which adds about 30 per cent to capacity for a given weight.

How accurate is the GAU-8?

Its specification is five milliradians, eighty per cent — eighty per cent of rounds land inside a cone five milliradians wide, which is a 40-foot circle at the design range of 4,000 feet. For comparison, the 20 mm M61 Vulcan has eight-milliradian dispersion.

Can the gun’s exhaust stop the A-10’s engines?

It did during early testing. The gun gas is essentially oxygen-free and caused flameouts. Production A-10 engines have a self-sustaining combustion section, and the igniters fire automatically whenever the gun is fired, which solved it.

Do other aircraft carry the GAU-8?

No aircraft other than the A-10 carries the full Avenger system. A four-barrel derivative, the GAU-13/A, was tested in a pod on F-16s during Desert Storm and abandoned. The Dutch Goalkeeper naval close-in weapon system uses the gun at sea.