I appreciate the chance to dig into it. It's always bugged me; the footage of these giant F-4s clearly dusting the shit out of MiG-17s, which are obviously a generation or two older, followed by the observation that clearly the fact that an F-4 occasionally got shot down was proof positive that they needed cannons.

And then you play even the most rudimentary flight sim and combat's gotta be fuckin' weird for it to be anything other than you and a blip on the radar trading air-to-air missiles. Go guns hot and you are useless.

Digging into it there's a lot of speculation as to why fighters need guns/why the F-4 needed guns and it seems to come down to this:

1) If you need to get close enough to look at it, and then decide you need to blow it up, it's good to have a gun. mmmmmmmmmmeh.

2) Early air-to-air missiles sucked ass and when an F-4 used up all its missiles, the MiG could eat it alive. mmmmmmmmaybe.

3) Rules of engagement in Vietnam required pilots to have visual contact on a MiG before they could engage it and by the time they were close enough, any advantages they may have had with standoff weaponry were erased. This one's truthy, although it's nowhere in this 56-page study from the Air Force's School of Advanced Airpower studies. but there is this:

American aircraft were prohibited from engaging MIG's except as

required to protect their strike forces. Even when chasing hostile MIGs, US fighters were not

authorized to attack North Vietnamese MIG fighter bases until 1967. One pilot explained the

situation by noting that "MIGs could wait on the end of their runway until they saw us fighters

approaching, then takeoff, make one turn, and wound up in shooting position on the trailing

flight of aircraft".

The passage directly before is telling:

MIGs and SAMs were the more advanced elements of the air defense system, but

antiaircraft artillery accounted for the most aerial kills. With air defense systems near their peak,

summary reports of aircraft losses from 1967-1968 indicate that AAA accounted for more than

seventy-five percent of all US aircraft shot down over North Vietnam.

11 Fighters loaded with

bombs normally defeated MIGs and SAMs by flying fast and at low altitudes. In Vietnam, this

tactic placed fighters within lethal range of the AAA guns.

It seems to loop back to the beginning, like Ouroboros eating its tail:

If you're only going to be given one plane, it better do fuckin' everything 'cuz you might end up painted into a really, really stupid corner.

I'll bet they'd put bayonets on the things if they could.