20mm cannon, best, worst, specs, comparison to LMG, HMG etc.

Ad: This forum contains affiliate links to products on Amazon and eBay. More information in Terms and rules

13 mm HEI-t with 1.4 grams (22 gr) PETN + 0.4 grams (4.6 gr) thermite 750 metres per second (2,500 ft/s), projectile mass 34 grams (520 gr), muzzle energy 9,560 joules (7,050 ft·lbf)

so 1.8 grams of explosive material. thats 6 rounds to = your eg of 11 grams @ 100% hit rate. or 12 rounds @ 50% hit rate. 1 gun. or 3/6 hits with both MG131's.

but these are just numbers.. means nothing.

a 'number' (haha) of years ago a fish wildlife cesna was hit by a single .22 by a annoyed hunter. it brought that plane down.. in a hurry. the pilot didn't know his plane was hit. He thought it was just a mech. problem.. until they found the bullet hole the bullet lodged in some electical wiring causing a short of the ignition system.
 
"For me a better hunting analogy would be comparing a .25-35 Winchester to a .375 H&H.
Both have similar velocities (approx 900 m/sec), and .375 bullets are about 3 times as heavy as .25-35s... just as 20mm are about 3 times as heavy as .50s.
You can take coyotes or antelope with a .25-35 reliably, but anything bigger than that and you are undergunned. The .375 will also take coyotes and antelope (bit messy), but it will also do the job on any other animal you might choose to shoot, up to and including large pachyderms."

But American fighters weren't hunting pachyderms, they were hunting rabbits. I would argue for using 20 mm cannon on anything tougher than a P47, but the German and Japanese planes we faced just weren't that tough.

The Japanese planes, aside from a the large 4 engine flying boats encountered now and then, weren't difficult to shoot down at all.

The toughest German planes we encountered were probably JU88' and maybe ME110-410's. From the gun camera footage I've seen, none of these targets were a problem for even a 4 gun Mustang, much less a P47.
 

I stand corrected on the HE content of the 13mm HEI round.

.50 cal Browning 862 metres per second (2,845ft/s, aircraft guns used shorter barrels than ground guns), but velocity varied with projectile, projectile mass 41 grams to 46 grams for the common WW II versions muzzle energy as high as 17,800 joules. The .cal bullets due to better shape and higher weight per unit of frontal area, retained velocity better and so hit proportional harder at longer ranges

AS for the rest, we are now getting into the "My golden BB is better/lucker than your golden BB" argument.

Given lucky hits any plane can down any other with one or two or three not very powerful rounds. How effective (or lucky) a particular round is depends on both it's type and the location of the hit. An AP round might just punch a hole were even a small HE round could cause critical damage and in another spot the HE round could explode too early and not reach the critical component an AP round could.
 

Considering it can take 4-6 years to develop (properly) an aircraft gun and ammunition, depending on your enemy NOT to develop better aircraft is pretty poor strategy. Unless your spy network is good enough to give you several years of warning

Please consider also that many Allied planes were equipped with gyro guns sights from 1944 on which greatly increase the accuracy of shooting, American planes switched from 50/50 belts of AP/incendiary to 100% (or nearly) of M8 API and in the spring of 1945 were also using some quantities of the M23 incendiary round which carried a much increase payload of incendiary material.
The "idea" that the .50 was good enough almost got the USAF in trouble in Korea. Despite using guns that fired 50% faster than the WW II guns and having radar range finders tied into the gunsights it may have been the better training of the pilots that allowed the USAF pilots to prevail.

The USAAC wanted faster firing guns as far back as 1940-41. Projects to increase the rate of fire include the T-21, T-22, T-25, T-26, T-27, T-28, T-34, T-35 and T-36. Some projects stopped in blueprint stage, some went through up to six variations/working examples.
These do not include .60 caliber projects or extra high velocity .50 cal projects.
 
the problem with 1944 all those 'victories' the allies were getting was the result of morphine addicted megalomaniac who went by the name of Hermann Wilhelm Göring. He gave a direct order in 1944 for all Luftwaffe fighters to ignore allied fighter escorts and only attack the heavies. no matter what. as a result the P-51s and P-47s had an easy job off picking off Fw190's and Bf109's as a result. how much the 50cals had to do with that? well, I think the 'Golden BB' holds true in this case.
 

They weren't hunting rabbits, they were hunting tigers and grizzly bears!

Sure, the Japanese planes were known to light up pretty easy, but you only have to watch a few gun cam vids on Utube to see the plethora of other things fighters shot at like trucks, tanks, trains, ships, barges, buildings, radar towers etc. Bigger guns are going to do a better job.

I haven't seen every gun cam clip that's available on the 'tube', but I did spend some time tonight to see if there was a difference between some p51/47 clips and Spitfire/tempest clips. The .50 armed guys get the job done, but the cannon hit planes go down quicker and show more explosions and structural failures, at least in the hour or so of clips that I watched.
Not saying this is definate proof of superiority of 20mm over .50s, but it does support the argument.
 
Last edited:

Let's see, Better gun sight that doubled accuracy in some firing situations, more effective ammunition, increased numbers of American fighters over Germany, declining standard of German pilot training all had nothing to do with it?

As I have said before, the .50 did the job, it wasn't the best at it.

We used to put out fires (mostly ) with 1 1/2 in hose and 95GPM Imperial nozzles. It's a bit easier, quicker and safer using 1 3/4 hose and 125-150gpm nozzles. Granted you use up the tank water quicker but I don't know of many (any) fire fighters who want to go back to the old gear, even if it is a bit lighter.
 

Your puttering along in your ME109 climbing up to intercept the B17's when a P47 comes screaming down from altitude, plants himself about 50 yards behind you and squirts a 3 second burst into your tiny little fighter plane. 300 plus armor peircing incediary rounds, set your fuel tank on fire, rips off a wing, penetrate your seat armor and splatters you all over your instrument panel.

What part of that scenario is a "golden bb"? It sounds more to me like, a more than adequate weapon doing its job.

When I think of a "golden bb", I think of that as maybe a door gunner hitting a speeding fighter with a couple of rounds that disable the pilot or aircraft. A very lucky hit.
 
Last edited:
well Bf 109's could hold their own very well against any allied fighter. with only two MG 131's and either a MG 151/20 or a Mk 108 cannon. point being of the 'Golden BB' was that with those orders the Luftwaffe Fighter pilots faced, it might as well have been 'Golden BB's' firing at them.

Granted, not every Luftwaffe fighter pilot aheared to those rules ( survivability took over ) many of the younger, inexperianced did. so whether it was 50's or .303's the end results were the same.
 
Except that tests had shown that the .5" didn't penetrate German armour, something that you insist on ignoring. Also Me109s Fw190s were usually at height, waiting for the bombers, not "puttering" up to get to them. Your comment about German pilots being rabbits has to be one of the worst insults ever directed at men (for whatever reason,) who were defending their homeland.
I don't know the total figures, since I have no interest in them, but it would pay to check Germany's actual losses, against claims made. The RAF got a shock, after the war, when they found that, in the second half of 1941, when they claimed 731 German aircraft, for a loss of 411, the true number was 154.
Edgar
 
My opinion is that the 20mm guns were in the pipeline for the Navy. They just didn't rewrite existing contracts and change existing delivery schedules to get them.

While I do not think the 20s were in the pipeline at the time the report was written, October, 1944, (They were still waiting for inputs from the fleet), they were certainly preparing for its possibility by building and buying aircraft with the capability of both the 20s and 50s. It is, however, apparent that the Navy had no urgent need to replace the 50s as the 20s remained on the backburner until the end of the war, and not finding it necessary to retrofit. It is also interesting to note in the report that not one single Naval representatives (over sixty, of which I am sure many had some combat experience and all had inputs from the fleet) demanded or even commented that their fighters needed more firepower, clear evidence that they felt comfortable with the 50s and considered them effective air-to-air weapons.
It is interesting to note that, while Commander Monroe was a proponent of the 20s, he was most excited about the high velocity 60 caliber.
I think this is a completely inadequate analogy to use. How many times do hunters take down running game with a rifle? A more accurate analogy is trying to shoot birds on the fly.
Or, perhaps they realized that the night targets are likely to be larger bombers and were non-maneuvering.

While I don't disagree with your comment about multiple targets, I do believe shooting birds with a shotgun is appropriate. Hunters use birdshot for birds and not buckshot. While the probability of kill for buckshot is close to one, the probability of a hit is quite low (of course cost may be a factor, but I am sure you understand the point.) I certainly do not agree with you that the 50 cal "almost got the USAF in trouble in Korea". Take for instance comparing a one second burst from the F-86 with six M3 50 cal, an F9F with four 20mm M2, and the Mig-15 with two NS-23, 23mm, and one N-37 37mm.

F-86, six M3s, rof 1250 r/min, total r/m 7500, total r/sec 125, throw weight/sec. 187.5 oz. (1.5 oz/bullet)

F9F, four, Hispano M-2s, rof 700 r/m, total r/m 2800, total r/s 47, throw weight/sec 141 oz (3.0 oz./bullet)

Mig-15 two NS-23s, rof 550 r/m, total r/m 1100, total r/s 18, one N-37, rof 450 r/m, total r/m 450, r/s 7.5, overall r/s 26 throw weight/sec 138.8 oz. (6.2 oz/23mm bullet, 27 oz/37mm bullet)

So, from a raw hitting power, not including the explosive power, standpoint, the six M3s of the Sabre does not give up anything to the F9F or Mig-15. While installation weight of the guns is roughly the same, 50s vs. 20s, the real advantage of the 20 is carried ammunition weight. For the probability of striking the target, the F-86 weapon package is much higher. All of this becomes moot after the fast firing M39 cannon comes along.

I think the comments about the F-86 making hits and the Mig flying away so there was a need for a bigger gun is not a logically supportable argument. It is analogous to a hunter, on seeing feathers come off a bird and it continues to fly, wanting to switch to buckshot to increase probability of kill once hit. Had the F-86 had 20s, with less than half the projectiles fired, it might have had a significantly lower probability of even hitting the Mig. In addition, that one, higher probability, injuring 50 cal, may have forced the Mig out of the fight, which is also significant. Also, I think that the highly penetrating 50 cal bullet is effective against the jet aircraft in that one bullet hitting the fuselage section from the turbine through to the pilot, has a high probability, close to one, of disabling or destroying a jet. That is a very large target.

Six 50 cal M3 is a powerful weapons package and, firing for one second, provides a massive wall of high energy projectiles, and, if striking, easily taking down any fighter, and most likely bomber. I don't think the AF was anywhere in danger from using it in the Korean War.
 

You need to go back and read everyones comments. People were making references to hunting: killing aircraft is like killing large animals. A B17 is a big tough animal, hard to kill, like an elephant, so you need 20 or 30 mm cannon, just like you need a .375 or larger for killing elephant. I said, US fighter pilots weren't hunting big hard to kill elephants, US pilots were hunting rabbits, little, delicate ME109's, easy to kill with smaller weapons like .50's. I was not talking about German pilots at all. After reading this comment, go back and read everyones posts and it should make sense what I meant

Ok, for arguments sake, the ME109 wasn't puttering up to altitude, he was instead REALLY moving fast, the .50 didn't penetrate the seat armor on the 109 from dead astern, instead, it shot off both wings, exploded the ammo and the fuel tanks, and shredded the canopy so it wouldn't open and the poor guy rode it all the way to the ground. Hey at least the armor wasn't penetrated, maybe they could recycle it and put it in the next ME109 coming off the assembly line.

ANYWAY, back to my original point, when you have 4, 6 or 8 .50's, with a pilot that can shoot, directly astern, you are in deep trouble in a plane no bigger than a 109 or a 190. If they hit a 109 or 190 with a good solid burst, it is more than likely going nowhere but down.
 
Last edited:
IIRC There was a test flight of F86's using 20 mm flown by the USAF in the Korean War and that were mixed with standard equiped 86's they used the 50cal armed 86's as decoys and found the cannon armed version more destructive. I have the article somewhere but in the mess of stuff I have will be hard pressed to find it
 
 
The problem with the .50 in Korea was that, air combat was done at such a high altitude, the incendiary ammo wouldn't set the Migs on fire, air was too thin. The fuel burned by the Mig was probably less flammable also. At least that it what I have read.

By Korea, it was time to move to the 20 mm.
 


I think you're understating the case for the Hispano:

A 20 x 110 round weighed 128-167 g – that's 4.5 to 5.9 oz, not the 3 oz you are using. Typically, experts like Tony Williams or Emanuel Gustin use 130 g as a round number - 4.6 oz.

Throw weight should be on the order of 210-270 oz per sec, with a 'typical' weight of about 215 oz per sec - significantly better than the M3 set-up on the Sabre.

I also believe you're mild overstating the RoF of the Browning and understating that of the Hispano, by about 50 rps in each case.
 

They may not have been in the pipeline in Oct of 1944 but they were certainly in the pipeline by Feb or March of 1945, Were ANY contracts placed for .50 cal armed fighters after march of 1945? Not deliveries taken on existing contracts but contracts for planes to be delivered 9 months to two years in the future?

I think this is a completely inadequate analogy to use. How many times do hunters take down running game with a rifle? A more accurate analogy is trying to shoot birds on the fly.

Both analogies are bad, most hunters using rifles don't fire bursts of 2-3 seconds (10-30 shots) on running game hoping to hit the animal multiple times "SOMEWHERE" in order to bring it down.

Neither do bird hunters actually fire a "burst". They fire once (or twice) and while they fire multiple projectiles that do form a pattern and do string out in length many of the other aspects fall down. Like the comparison of buckshot to bird shot. Six .50s in WW II could put out about double the rounds per second of four 20mm guns. This is about the same as a change a couple of shot sizes. like from 7 1/2s to 5s or 6s to 4s. For buckshot is like going from #3s to #0
Or, perhaps they realized that the night targets are likely to be larger bombers and were non-maneuvering.

And that means what? That the 20mm guns fired into larger area at the same distance and were more likely to miss a fighter?
If four 20mm guns were expected to damage/destroy a bomber in less exposure time than six .50s why wouldn't they do the same thing to a fighter that needs fewer hits to bring down?
part of the fighter vs bomber and maneuvering argument comes from the German/Japanese 20mm cannon. These had lower muzzle velocities and longer flight times than the Hispano and needed more lead than the .50 in order to get hits making defection shooting much more difficult. This doesn't really apply to the 20mm Hispano vs .50 cal Browning argument because both guns had an almost identical muzzle velocity and while the .50 does retain it's velocity better the higher you go into thinner air the less difference there is and at practical fighting differences even at low altitude the difference is nowhere near as great as the difference between the .50 and the axis guns.



This has been covered pretty well by Jabberwocky. I will add that the the six M3 .50s with 267 rpg ( 13.4 seconds of firing time) of the F-86 weighed 353 kg, while the four M3 20mm (not WW II M2s) of the F9F Panther with 190rpg (15.2 seconds firing time) for 363kg. Ignoring the HE power certainly skews things towards the .50 but hardly reflects reality.

Back to the bad hunting analogies, Try using a hunter, that upon shooting at ducks, or geese or even turkeys with #6 shot and failing to bring home many changes to #4 shot, not buckshot. The Russian 37mm may have been buckshot.
I think we can stop with the SUPER.50 stuff. While it was a fast as a speeding bullet, it was not more powerful than a locomotive and it could not leap tall buildings in a single bound. The chances of a .50 cal making through the Fuselage skinn are better than some people claim but the chances of it going though substantial parts of the engine are a lot slimmer. And then we are supposed to believe that WONDER bullet can keep going and hit the pilot? Through the fuel tank and seat back?
And of course an AP 20mm projectile could not do the same thing? Or a 20mm HE or AP projectile into the engine turbine wouldn't stop it?

A massive "wall" of 120 projectiles in the time it takes for the target to travel 800-900ft.
 
 
Best thing to 'shoot' an elephant with is a camera -
you are 100% correct my friend. I havn't harmed an animal since 1990. it was stupid to do then and equally stupid to do now.

that said, I looked at tons of gun footage of MG151/20 vs M2 .50.. all I can say it, hit for hit, the 20mm is much more devestating. another thing I noticed is that once an figter a/c gets hit by the 20mm.. they become sitting ducks. Also, intresting little factoid, a stern attack from a 20mm on a -17 requires around 20 hits to disable/destroy it. Whereas a frontal 20mm attack on a -17 requires only about 4-5 hits to disable/destroy it.

.50s seems to take much longer to get the fighter a/c disabled/destroyed.
 

Users who are viewing this thread