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I noticed that the "new" F-35 still has a GAU-22/A cannon installed in it -- albeit with only 182 rounds (more with ammo pods).

Why do fighters still have cannons? The day of dogfighting is long over, now it's just fire some missiles and forget. Even if they expended all their missiles, 182 cannon rounds is only 6 seconds of firing (I think the GAU is rated to 1800 rpm).

The only reason (and I'm not sure if I should answer my own question) is that they need something to shoot warning shots over the bow of another airplane. But that seems an awful amount of weight for this rare occasion. And it'd mean loading tracer rounds.

Or is just a vestigial organ, like the sabres on the side of full dress military uniforms?

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    $\begingroup$ For the same reason Marines still get Bayonets to attach to their M16: Just in case you need to get up close and personal. $\endgroup$
    – WernerCD
    Commented Sep 22, 2014 at 22:15
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    $\begingroup$ And from what I remember, 6 seconds is similar to the amount of time you could spend firing the guns on a Spitfire in WW2; that's quite a lot of time if you're not indulging in spray and pray. $\endgroup$
    – JamesF
    Commented Sep 23, 2014 at 3:07
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    $\begingroup$ He's too close for missiles, Goose, I'm switching to guns! $\endgroup$
    – J...
    Commented Sep 23, 2014 at 9:56
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    $\begingroup$ If there was not a gun, how many more missiles could there be? If less then 1, then the gun seems like a good ideal, if only for taking shots at the ground. $\endgroup$
    – Ian Ringrose
    Commented Sep 23, 2014 at 13:12
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    $\begingroup$ "WHAT? A hot air balloon full of Dynamite heading for Gotham? Scramble the fighter jets." -"Errm, sir. The balloon is mostly cloth and basket reeds, our missiles can't get a lock on that" "Arse! I knew we should have installed guns, well tell the pilots to fly directly through the balloon, lets see what happens" $\endgroup$
    – Mikey Mouse
    Commented Sep 24, 2014 at 15:13

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The idea that missiles will be all a fighter aircraft needs was prevalent in the late Fifties. The McDonnell-Douglas F-4 Phantom II carried initially only missiles, but at the start of the Vietnam war this turned out to be inadequate. The long-range missiles back then were rather unreliable, and in a real conflict things turn out always different than anticipated. As von Clausewitz said, the plan is the first casualty of war.

F-4s frequently found themselves in close-combat situations for which they were inadequately prepared. Even today, a gun gives the pilot a lot more options, and if the situation is unclear, close-up visual inspection before shooting is still vital to avoid politically embarrassing situations.

From the F-4C on, F-4s were equipped with a gun. First in external pods, from the F-4E as an internal gun. What also helped to make the F-4 more effective was better training for pilots and ground crew, so the missiles were in better shape and better applied.

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    $\begingroup$ Probably a tradition by now, though. In the Gulf war, the only air-to-air kill made with a gun was an A-10 gunning down a helicopter, and the A-10 isn't a fighter jet. In fact, during the Gulf War fighters scored more air-to-air kills using bombs than bullets (!!) $\endgroup$
    – MSalters
    Commented Sep 22, 2014 at 21:47
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    $\begingroup$ Besides missile unreliability, another factor handicapped missile-only F-4s in Vietnam. The rules of engagement required that enemy planes be identified visually before being shot at, and this was impossible at missile ranges. F-4 pilots either had to violate their ROE, or make a close pass for identification, defenseless, then try and open the range back up to engage with missiles. This is still potentially an issue in modern combat environments. $\endgroup$
    – Russell Borogove
    Commented Sep 22, 2014 at 21:50
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    $\begingroup$ AWACS can't positively tell you if a non-radiating target is friend or foe, and you can't guarantee AWACS will be available when you need it. $\endgroup$
    – Russell Borogove
    Commented Sep 23, 2014 at 0:00
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    $\begingroup$ and in a heavy jamming environment, that missile is going to lose a lot of its reliability. Bullets aren't fooled by chaff and flares, or ECM gear. $\endgroup$
    – jwenting
    Commented Sep 23, 2014 at 3:24
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    $\begingroup$ @MSalters : because in the Gulf war there was no big aerial battle between similar forces. It mostly was one force bombing the (much worse-equipped and smaller) other force before they even could take off. Had they faced a similarly-equipped large air-force in the air, there would have probably been at least a few dogfights. $\endgroup$
    – vsz
    Commented Sep 23, 2014 at 18:37
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I guess it's for the same reason that soldiers carry hand-guns.

They designed the F-4 without a cannon and added them back in 1965.

If you do go up to intercept a plane, if you do ever get close to it, what then? The minimum range of a sidewinder is 2.5 km.

This paragraph says,

Starting with block 50 (as far as the F-16 is concerned anyway), provisions have been made to fire the new 'hotter, faster, farther' PGU-28 round. It reputedly travels three times as far as the standard M53 round, effectively closing the gap between the Sidewinder minimum engagement range and the gun's maximum engagement range.

Up-close and personal is the norm in peace-time: e.g. the Chinese buzzing American planes n the China Sea; or NATO planes flying to meet Russians in the North Sea or off Alaska. What would you do without a short-range weapon? You would have to:

  • Keep your distance (e.g. run away if the enemy comes too close)
  • Shoot before they get too close (a huge over-reaction)
  • Be unarmed/disarmed at close range (not exactly "armed forces" then, is it).
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    $\begingroup$ Theoretically, the new round doesn't so much "close the gap" as provide an overlap. The nominal effective range of the Vulcan with M53s is about a thousand feet, which is about the AIM-9's minimum range. $\endgroup$
    – KeithS
    Commented Jun 22, 2015 at 21:40
  • $\begingroup$ I may be naive, but to me it also seems like a good investment. Most guns won't cost as much as rockets. If they end up being used at some point and save one 100 million dollar jet in one instance, great. You end up not having too many rockets on those things, do you $\endgroup$
    – bytepusher
    Commented Jun 22, 2020 at 20:08
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You can't spoof a bullet with countermeasures.

The plain fact is that bullets cannot be diverted or fooled, unlike missiles, for which there are flares, chaff and different electronic countermeasures and early warning systems. It' s also much easier to destroy a plane with bullets now than it was a few decades back (during WW1 and 2 for instance). Unless your aircraft has some serious armor plating to guard against explosive and incendiary rounds which are quite common, it's difficult to guard against bullets

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    $\begingroup$ en.wikiquote.org/wiki/Team_Fortress_2#Meet_the_Heavy - "Some people think they can outsmart me. Maybe...maybe. I've yet to meet one that can outsmart bullet." $\endgroup$
    – user33
    Commented Sep 25, 2014 at 21:53
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    $\begingroup$ It would seem likely that enemies which develop countermeasures might keep them secret until they can benefit from the surprise of using them. The presence of guns would seem to offer some insurance against the possibility of encountering an enemy against which we have no effective weapons. $\endgroup$
    – supercat
    Commented Sep 25, 2014 at 22:30
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    $\begingroup$ I see a lot of comments to the effect of "can't jam a bullet" while true, let's not forget that cannon targeting systems CAN be jammed. This reduces the pilot to having to rely on manual aiming, which would be ridiculously difficult for someone who has always relied on their radar-augmented targeting system showing them where to shoot, but still doable. $\endgroup$
    – MishaP
    Commented Sep 20, 2018 at 13:57
  • $\begingroup$ Nice point and also a reason why we don’t believe in computers to do the right thing, instead we trust pilots. When it becomes serious, it necessary to do things manually. $\endgroup$
    – Peter
    Commented Feb 8, 2019 at 23:27
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Better to ask a combat pilot I would think. However, a few points:

The internal gun for the F-35A, including a full load of ammunition, is less than 500 pounds - this represents about 2.5% of the F-35's total weapons payload capacity. That doesn't really sound too bad. They can save 80 lbs if they choose not to load it.

The external gun, which is what the VTOL/Naval B and C models get, is a few hundred pounds heavier than that, but optional.

Six seconds is actually a lot of 'gun time' for modern air-to-air systems considering speeds, targeting systems and lethality of the projectiles involved. It's not like WWII anymore where you'd slowly pull up behind a bomber and then have to spend several seconds pumping a bunch of crappy .50-cal lead in, hoping to poke enough holes in an oil cooler to make a difference.

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A long time ago I used to build fighter aircraft (yes, with my hands). Anyway, the designers whispered behind their hands that the guns on this particular aircraft were there to make the pilots feel happy. The gunfire vibration tended to destroy the delicate instruments, so they were strongly discouraged from ever firing them.

In those days the designers (I was aspiring to be one) said, only half joking, an aircraft is a platform for delivering missiles or bombs, so it is basically a radar and a missile management system. The rest is infrastructure.

So in folk-parlance pilots like to have guns, in the same way as the air force likes to have pilots - it makes them feel better but is not strictly necessary.

edit: chatting to my old colleague about this, he said he offered to give a pilot a loudspeaker in his helmet going "Da-Da-Da-Da-Da", since it would be just as much use and a lot less weight. But the pilot was unimpressed.

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    $\begingroup$ Electronics certainly were delicate back then, so the designers had a point. Today, however, the gun vibration should be manageable. Specially designed circuits can survive being shot from a tank's gun with more than 10,000g peak acceleration. $\endgroup$
    – Peter Kämpf
    Commented Sep 23, 2014 at 19:44
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    $\begingroup$ @Graham Actually that is the best solution. Changing the tail design that far in the R&D cycle is going back to the drawing board. I suspect someone in management spent time designing military land vehicles. Same chassis; Different guns, and find a way to fit that cannon into it. $\endgroup$
    – workoverflow
    Commented Jul 1, 2018 at 7:11
  • $\begingroup$ @The problem wasn't the tail per se, it was that they'd been told to fit the countermeasures to the aircraft body. But they went ahead and bolted them on the tail instead, with results which they'd been warned about. $\endgroup$
    – Graham
    Commented Jul 1, 2018 at 13:49
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As missile guidance and tracking systems evolve, so do countermeasures and maneuvers to cause a missile to miss. Planes don't carry that many missiles to begin with, and as mentioned before, missiles also have a minimal range. For all of these reasons, guns are still the only way to hit a plane with modern countermeasures. After all your missiles went for bust, or you're closer than the minimal operating range of your missiles. Turning away to gain distance is usually not an option, because as you increase your distance from the enemy, you open up an opportunity for them to turn in and engage you, not to mention losing airspeed is still generally considered a blunder in air-to-air combat.

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While missile and radar systems designs get better they still cannot make a complete positive identification between friend or foe. So you need to get close enough to visually ID the target. Now you are in a dogfight situation with distance getting too close for missiles and too far for a gun. So you need both. You also still need to train pilots in close in dogfighting techniques and tactics.

All of this is complicated by the fact that aircraft are sold to many countries. So the same aircraft may be flown by both sides of a conflict. So now you need to get very close to see markings and other distinguishing characteristics.

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The short and sweet answer: Guided missiles have yet to demonstrate a Probability of Kill (Pk) or effective operating envelopes for all combat situations which can be entered into and a gun can fill those gaps well. Gunfighting has certainly been viewed with disdain by Pentagon planners who have been repeatedly trying to do away with them in fighters despite the record of missiles in combat. While improvements are constantly made to guided missile designs, the gun appears to be an integral component of era combat well into the future.

Also NEVER CONCLUDE THAT DOGFIGHTING IS OVER. ACM is and always will be the fundamental and ultimate form of air combat. The beginning and the end of the process. I don’t give a hoot in hell what some idiot F-35 fanboy or defense OEM brochure or promo video has to say about that. History is on the side of the dogfight. Ignore that at your own peril.

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  • $\begingroup$ I agree with you on how missiles are not effective at all ranges, but they are still very effective at most ranges. However guns are not very effective because dogfights are a thing of the past. As much as I love the traditional dogfight, modern air combat happens with both planes flying very far away from each other, and even if they are close the gun is of no use because it does not carry enough rounds and it does not do enough damage. Even a skilled pilot would miss many shots and the ones they hit wouldn't be enough. $\endgroup$
    – J Lopez
    Commented Apr 13, 2020 at 19:41
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    $\begingroup$ If you think the dogfight is over, I’ve got some swamp land in Arkansas to sell you for $20 million an acre. Missiles fail at critical times. ROEs prohibit taking a shot without a visual ID on the bogey, stealth aircraft vs stealth aircraft prohibit such attacks, etc. There are many reasons why reliance on pure missile air to air warfare is fallacious. $\endgroup$
    – Romeo_4808N
    Commented Apr 14, 2020 at 6:24
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Traditionally, fighter aircraft are armed with guns. The gun is a versatile weapon, effective at short ranges against both air and ground targets. The idea of using a $150,000,000 aircraft to strafe the roads seems highly questionable, though. In the World Wars, a fighter was very much an expendable asset. Today that's no longer the case.

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  • $\begingroup$ Assume you don't mean the actual road- too easy to fix, but rather road vehicles. $\endgroup$
    – user2617804
    Commented Mar 19, 2023 at 4:45
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When radar stealth technology came to prominence in the 1980s there was widespread speculation that air combat would revert to a form similar to that seen in the First World War. This prediction has not been fulfilled, partly because the adoption of radar stealth technology has been quite slow, and partly because of continuing improvement in the effectiveness of air to air missiles.

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  • $\begingroup$ The development of optical wavelength missile guidance systems, such as that used in the AIM9R Sidewinder is also a factor to be considered here, since these work well against targets with low IR and radar signatures. $\endgroup$
    – J. Southworth
    Commented Aug 31, 2018 at 10:19
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I would also suppose that cannons/guns would be useful against ground targets in certain situations, e.g. tanks or artillery installments.

For example, the A10 Warthog's bread and butter is its main cannon. Though this plane is primarily designed with the elimination of ground targets in mind. (As someone noted the A10 is an attack aircraft. I'm merely noting this aircraft's reliance on its cannon for ground attacks as a justification for the above supposition. Fighter jets may occasionally be in situations where attacking ground targets is necessary.)

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    $\begingroup$ Welcome to Stack Exchange. Please note that we prefer answers that either include reasoning or are backed up by solid sources. "Some anonymous person on the internet thinks it might be for shooting at targets on the ground" doesn't really help very much. $\endgroup$
    – David Richerby
    Commented Sep 24, 2014 at 7:13
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    $\begingroup$ It is not the primary role of a fighter to attack ground targets, especially not with guns. Note that the A*10 is not a *Fighter jet, but a ground Attack aircraft. $\endgroup$
    – DeltaLima ♦
    Commented Sep 24, 2014 at 8:16
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    $\begingroup$ But most of the reason for having ground-attack aircraft is that fighters and fighter-bombers are not well suited to that role. $\endgroup$
    – David Richerby
    Commented Sep 26, 2014 at 7:34
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    $\begingroup$ In theory, the F 35 is supposed to replace the warthog in a ground assault role eventually. Most modern fighters are multirole, and the ability to dogfight (which is where canons are useful) and the ability to strafe may be useful. $\endgroup$
    – Journeyman Geek
    Commented Sep 28, 2014 at 7:43
  • $\begingroup$ @JourneymanGeek But isn't that, like the F-15E, primarily air-to-ground with bombs, whereas the A-10 is air-to-ground with the cannon. $\endgroup$
    – David Richerby
    Commented Sep 28, 2014 at 16:38

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