The F-4’s Biggest Upgrade: Its M61 Autocannon

An Easy Fix?

The F-4E variant of the Phantom was the most widely produced of the F-4s. Why? Because it included a 20mm M61 Vulcan autocannon. 

Before this variant, the previous versions of the Phantom didn’t have an internal gun and instead relied on missiles to inflict damage. An external gun pod could have also been mounted (instead of the M61 Vulcan) but those were often seen as unreliable and inaccurate in most cases.

The rules of engagement during the Vietnam War required visual identification of enemy aircraft, which often meant the target was too close to be engaged with missiles. And so, when the gun was introduced, it immediately showed how successful it can be. 

The gun alone claimed about half a dozen victories over enemy MiGs. Since the F-4E, all US fighter aircraft have included an internal gun. It’s easy to see why!