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GAU-12 Equalizer

Marines on a flight line feed a belt of 25 mm rounds into an open gun pod under the belly of an AV-8B Harrier
Marine Attack Squadron 214 ordnance technicians load 25 mm rounds into the GAU-12 pod of an AV-8B Harrier at Eielson Air Force Base, Alaska, June 2010.Photo: Lance Cpl. Aaron Diamant. Public domain, work of the US federal government, via Wikimedia Commons (accessed 2026-10-27).

Drafted — not technically validated

Record revision 1 · The Marine Corps Harrier's five-barrel 25 mm gun, carried in a belly pod; the F-35's GAU-22 is its four-barrel cousin.

Real-world weapon as described in public sources. Weights and dimensions change with the fins, fuzes and variant fitted; the data plate names the variants its figures describe, and differences are noted beside the number they affect. The record describes the weapon; it is not a guide to employing it.

GAU-12/U Equalizer 25 mm rotary cannon · GAU-12/U

Type
Five-barrel 25 mm Gatling-type cannon [1]
Origin
United States; designed by General Electric, built by General Dynamics [1]
In service
Developed in the late 1970s for the AV-8B Harrier II [1] [2]
Weight
270 lb (122 kg) with its feed system [1]
Dimensions
Length 83.2 in (2.11 m) [1]
Calibre
25 mm, firing NATO 25 × 137 mm ammunition [1]
Action
Based on the mechanism of the 30 mm GAU-8GAU-8 Avenger OrdnanceThe A-10’s seven-barrel cannon: rotary operation, ammunition, aircraft integration and the meaning of its published firing figures.; driven by an 11 kW electric motor, or in external mounts by a bleed-air pneumatic system [1]
Rate of fire
Normally 3,600 rounds per minute, at most 4,200; limited to 1,800 in the AC-130 gunship [1]
Muzzle velocity
3,400 ft/s (1,040 m/s) with high-explosive incendiary rounds [1]
Ammunition
Linked or linkless 25 mm rounds [1]
Carried by
  • AV-8B Harrier IIAV-8B Harrier II AircraftA vectored-thrust jump jet: vertical or short take-off, flown by the US Marines for close air support. [1] [2]
  • AC-130 gunship; the four-barrel GAU-22/A arms the F-35 [1]
Variants
  • GAU-22/A: lighter four-barrel version for the F-35 [1]

A smaller Avenger

The Equalizer was developed in the late 1970s from the mechanism of the 30 mm GAU-8 AvengerGAU-8 Avenger OrdnanceThe A-10’s seven-barrel cannon: rotary operation, ammunition, aircraft integration and the meaning of its published firing figures., scaled to fire a new NATO series of 25 mm ammunition. It is about the size of the 20 mm M61M61 Vulcan OrdnanceThe six-barrel 20 mm Gatling gun that has armed US fighters of every service since 1959.. [1] [2] An 11 kW electric motor turns it, or in external mounts a pneumatic system driven by engine bleed air. [1] It normally fires 3,600 rounds per minute, at most 4,200. The AC-130 gunship limits it to 1,800, to save ammunition and barrel wear. [1]

In the Harrier

The gun was developed for the AV-8B Harrier IIAV-8B Harrier II AircraftA vectored-thrust jump jet: vertical or short take-off, flown by the US Marines for close air support., which carries it in two pods on the belly: the gun in the port pod and its ammunition in the starboard one. The US, Italy and Spain all mount it in their attack jets. [1] [2] A lighter four-barrel version, the GAU-22/A, arms the F-35. [1]

Sources

  1. GAU-12 Equalizer. Wikipedia (secondary source). https://en.wikipedia.org/wiki/GAU-12_Equalizer (accessed 2026-10-27).
  2. GAU-8 Avenger. Wikipedia (secondary source). https://en.wikipedia.org/wiki/GAU-8_Avenger (accessed 2026-10-27).

Wikipedia articles are secondary sources and can change; they are cited with the date they were read. NAVEDTRA training manuals and budget justification exhibits are official US publications, but each describes the weapons in service when it was written.