Top Gun

The following weapons were used in the film Top Gun:

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Top Gun (1986)

Pontiac M39

While not shown firing, the Northrop F-5E & F-5F Tiger II fighters representing the enemy "MiG-28" fighters can still be seen armed with their Pontiac M39 cannons mounted in the nose forward of the canopy.

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Pontiac M39 20mm

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A MiG-28 firing its fictional guns at "Iceman's" plane. While the MIG's are seen firing "Gatling-type" guns from the wing roots, the two M39 cannons are still visible in the nose of the aircraft.

M61 Vulcan

Although not shown being fired in the film (despite the pilots "switching to guns" multiple times), the F-14A Tomcats flown by the protagonists are armed with internally-mounted M61 Vulcan cannons.

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M61 Vulcan 20mm

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The gunpod is seen at the bottom of the nose of Maverick's F-14A Tomcat.

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Maverick and Iceman's F-14A's on the flight deck of the USS Enterprise after the final dogfight; the firing ports for the M61 Vulcan can be seen near the nose of each aircraft

Trivia

In reality, the F-14 Tomcats would be using M61 Vulcan 20mm cannons, and even though both jets are seen using the same guns, the Russian MiG-28 would not be using the same guns. In reality, the MiG-28 does not exist; Mikoyan Gurevich has only used odd numbers for their aircraft (MiG 25, 29, 31, and so on).

The M61 Vulcan cannons on the F-14 are internal, you shouldn't be seeing them fire other than a muzzle flash from the cannon port on the left side of the forward fuselage far below the cockpit.