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

[Shortround6]

I was just counting fighters

Throw in the attack planes and bombers and the numbers really go up.

Early Skyraiders had 2- 20mm guns but then so did many of the Helldivers but they were before the Winter of 44/45.

 

[zjtins]

So how may Migs did a Skyraider shoot down? Nice data but not germaine. 1 in Vietnam I am aware of, never heard of any Skyraider air combat in Korea.

Side note, the US Navy went to 40MM on their ships in 44/45 because the 20mm could not effectively bring down Kamikazes.

FWIW I talked to a South Vietnamese Spad Pilot years ago. He loved the plane, easy to point on target, heavy weapons load, reliable. One comment that sticks out was he wished he had 4x.50 because he could carry more rounds. I think this was meant as reference to time on station. Skyraiders were ground attack craft, not fighters. Apparently whatever he shot at he must have felt the .50 was sufficient and the 20mm left him less time of fire.

 

[Shortround6]

Changing the argument?

"Side note, the US Navy went to 40MM on their ships in 44/45 because the 20mm could not effectively bring down Kamikazes"

True but then the ranges were rather different for AA and air to air.
Or are you suggesting that they should have gone to 40mm aircraft guns?

And why had the Navy gone to mounting 20mm AA guns wherever they could in 1942/43?

Because the .50 Machine gun as an AA weapon wasn't doing much of anything. Lexington and Saratoga both having 48 .50 cal AA guns at one point early in the war. A mistake in removing them?

Or is comparing guns in different usage not telling us much.

 

[zjtins]

The point of showing the 20mm was not adequate is a specific situation shows the complexity of comparing any weapon system. In this case at short range an incoming radial engine fighter (or light bomber) could not be stopped with 20mm in time. Hence there are limits to the 20mm effectiveness. The fact they moved from .50 cal to 20mm to 40mm does not change the discussion about fighter air to air armament effectiveness. It does show that even quad 20mm cannot stop a fighter quickly enough to protect a ship.

 

[zjtins]

Here is your reference not even from a book!

http://www.adlertag.de/waffen/guns.htm

MG FF/M:

The MG FF/M was a motor cannon with 20 mm caliber. This gun was manufactured in Germany under licence, but it was developed by Oerlikon in Switzerland. The MG FF/M was 1338 mm long at a weight of 26,3 kg. The cadence of this weapon was 540 rounds per minute at max, the speed, the projectiles got, leaving the muzzle was 700 meters per second.
The cartridge had a weight of 202 g, 134 g apportioned to the projectile. The ammunition was stored in magazines.
Deployed by the Luftwaffe in 1935 it soon became obsolete, because the penetration was not enough to destroy the heavy allied bombers anymore. The MG FF/M often got jammed or the shells broke, what didn´t make this weapon very reliable.
The MG FF was mounted in nearly the whole "Bf 109 E" family, the "Bf 109 D" and the "Bf 109 F-0" and "F-1". It was als well used as wing armament, as also as motor gun.

Further info from this forum.
MG FF

Incidentally, I believe that the 60-round drum was normally only loaded with 55 rounds as it was more reliable that way.

Which make sense as the spring gets tight, cartridge feed changes for many weapons, rifles pistols etc.

 

[Shortround6]

The point of showing the 20mm was not adequate is a specific situation shows the complexity of comparing any weapon system. In this case at short range an incoming radial engine fighter (or light bomber) could not be stopped with 20mm in time. Hence there are limits to the 20mm effectiveness. The fact they moved from .50 cal to 20mm to 40mm does not change the discussion about fighter air to air armament effectiveness. It does show that even quad 20mm cannot stop a fighter quickly enough to protect a ship.

The .50 cal or 20mm AA weapon was trying to destroy an airplane that was within 1000yds of the ship and if doing 300mph was under 7 seconds from impact even if hit at 1000yds. The 40mm was both more destructive and extended the engagement range to 2500-3000yds. A fighter on CAP would engage the target at a considerably grater distance from the ship. The fighter still needed to destroy the target instead of forcing it down. But it had more time to work with after knocking pieces of the target. If the Shipboard guns didn't inflict sufficient damage at a long enough range the target aircraft went "ballistic", meaning even with pilot dead and large pieces of the aircraft missing (control surfaces, parts of the wing, etc.) the main body of the aircraft would still impact the ship SOMEWHERE. Blowing 10ft or so of wing off the target aircraft when it is still 5-10 miles from a ship pretty much guarantees the aircraft will not hit the ship.

BTW, by the summer of 1945 the Navy didn't want 40mm AA guns, they wanted automatic 3" guns with proximity fuses. But since they couldn't get them they were settling for the 40mm guns.

Claiming that since the 20mm could NOT do the job wanted as an AA gun and therefor the Army and Navy should have stuck with the even less effective .50 cal guns for Air to Air weapons because they were good enough MOST of time isn't very logical.

BTW, the F-86 was the last Air Force fighters bar two that carried .50 cal guns and since both of them were modified versions of earlier aircraft I think we can see were even the US Air Force was headed.

 

[Glider]

The point of showing the 20mm was not adequate is a specific situation shows the complexity of comparing any weapon system. In this case at short range an incoming radial engine fighter (or light bomber) could not be stopped with 20mm in time. Hence there are limits to the 20mm effectiveness. The fact they moved from .50 cal to 20mm to 40mm does not change the discussion about fighter air to air armament effectiveness. It does show that even quad 20mm cannot stop a fighter quickly enough to protect a ship.

The point is that the fighter with 4 x 20mm will do a lot more damage, faster than a fighter with 6 x 0.5 mg. This can easily make the difference between the attacker reaching the target or not. There is a reason why the F6F5 could have been been armed with 2 x 20 and 4 x 0.5 had the US 20mm been reliable.

 

[zjtins]

The point is that the fighter with 4 x 20mm will do a lot more damage, faster than a fighter with 6 x 0.5 mg.

But that was not my comment. It is that the 6 or 8 .50 were good enough for the day, and did not see a need to switch to 4x20mm. In WWII the US did not have production capability of either 20mm guns or ammo. They could produce massive amounts of .50 guns and ammo.

Nor did I claim the US should stick with the .50 for Kamikaze as AAA. I brought it up to show there were situations where the 20mm was NOT effective.

A related fact is the Germans said it took 26x20mm shells to bring down a B-17 while only 3x 30mm (all averages). So their choice was to develop a 30mm they could put on anything at the cost of very low MV. I do not remember ever reading of a large change in bomber loss rates when this put into service. So merely comparing round energy seems to be unrelated to effectiveness in combat. There must be other factors that were more important.



And back to 'alot more damage' I disagree from the combat result for the fighters that used 4 (or even 2) 20mm. The results were around the same. Germans were known to shoot down 5+ planes a day with the FW-190 but not with the ME-109. The USAAF had about the same success with the 6 or 8 .50 cal setup. They did it with different damage types. The explosive shells tend to shred lightweight parts over a larger area. The .50 cal damage hard parts, (engine props, etc.) when they actually hit them. So it s trade of similar hit probability vs end affect.

Also the USAAF never had reliable 20mm it was not really an option. They went through at least 4 versions before ending up with the Colt version around 1958 or so. I can't find any discussion as why the P-38 did not swap out the 20mm for a .50. But in the East many B-25's were converted and then an actual standard version with a hard nose and 8x .50 plus 4 on the sides was created. Again probably because the .50 was plentiful and got the job done.

As I said before simply looking at only technical specs is of no consequence. In war you fight with what you have and modify/invent as needed.

Also in the Eastern theater the USAF quickly added semi armor piercing incendiary rounds to ignite the unarmored Japanese fuel tanks which appears to have been extremely effective. In this case 20mm discussion is moot as the .50 was sufficient.

 

[Jabberwocky]

But that was not my comment. It is that the 6 or 8 .50 were good enough for the day, and did not see a need to switch to 4x20mm. In WWII the US did not have production capability of either 20mm guns or ammo. They could produce massive amounts of .50 guns and ammo.

Ref the bit in bold, this is patently false. The US produced more than 135,000 Hispano derivative (AN/M1, AN/M2) cannons during WW2, including more than 56,000 before the end of 1942, 12,000 more than the original production contract called for. Planned for production capacity was for 9000 cannon per month, but with three different plants producing Hispanos, there was actually capacity for better than 15,000 guns per month.

A related fact is the Germans said it took 26x20mm shells to bring down a B-17 while only 3x 30mm (all averages).

Actually, the Luftwaffe estimated it took 18-20 20 mm shells, and 3 to 4 30 mm shells to down a heavy bomber, with the B-17 being slightly tougher, around 20-25 20 mm shells.

Also in the Eastern theater the USAF quickly added semi armor piercing incendiary rounds to ignite the unarmored Japanese fuel tanks which appears to have been extremely effective. In this case 20mm discussion is moot as the .50 was sufficient.

SAPI (actually M8 API) .50 cal ammunition was eventually a standard load-out for the M2, about 50% of the belting by late 1943 (along with ball, tracer, AP-tracer and standard AP). Its introduction had much more to do with the increasing levels of armour protection on German and Italian bomber and fighter aircraft in 1940-1941, and British research to that effect shared with the US, than it did with the comparatively fragile aircraft in the Pacific theatre.

 

[Glider]

But that was not my comment. It is that the 6 or 8 .50 were good enough for the day, and did not see a need to switch to 4x20mm.

For the USAAF I would agree with this comment, but for the USN they clearly wanted to go to 20mm as fast as they could. I think we agree that if a bomber bombs an airfield the damage one bomber can do is very limited no matter how lucky they get. One bomber is all it takes to take out a carrier. Lets say that using 4 x 20mm it saves 20 seconds. At 300 mph thats approx 1 1/2 miles in distance easily the difference between staying in the fight or being knocked out of the battle. To the USN every second counted which is why they wanted to change to the 20mm on the F6F5 and tried to get the Corsair armed with 20mm.

In WWII the US did not have production capability of either 20mm guns or ammo. They could produce massive amounts of .50 guns and ammo.

They also could and did produce lots of 20mm, the fact it was useless wasn't the fault of the producers, but the designers.

Nor did I claim the US should stick with the .50 for Kamikaze as AAA. I brought it up to show there were situations where the 20mm was NOT effective.

That I understand and your comments on the 40mm as well.

A related fact is the Germans said it took 26x20mm shells to bring down a B-17 while only 3x 30mm (all averages). So their choice was to develop a 30mm they could put on anything at the cost of very low MV. I do not remember ever reading of a large change in bomber loss rates when this put into service. So merely comparing round energy seems to be unrelated to effectiveness in combat. There must be other factors that were more important.

Remembering that on the Me109 you could only carry one weapon there is logic to making it as effective as possible. I am ignoring the extra 2 x 20mm as it had such a serious impact on performance. It worth remembering that the RAF and France post war used the german ideas and produced the Aden and Defta 30mm cannon, guns widely used in many nations so there must have been some logic to the approach.

And back to 'alot more damage' I disagree from the combat result for the fighters that used 4 (or even 2) 20mm. The results were around the same. Germans were known to shoot down 5+ planes a day with the FW-190 but not with the ME-109. The USAAF had about the same success with the 6 or 8 .50 cal setup. They did it with different damage types. The explosive shells tend to shred lightweight parts over a larger area. The .50 cal damage hard parts, (engine props, etc.) when they actually hit them. So it s trade of similar hit probability vs end affect.

On this we will have to disagree. A 0.50 bullet is normally going to knock a small hole going in and a small hole going out. If it hits something then there is a good chance that the object will be seriously damaged or destroyed. A 20mm is going to cause a hole going in and all sorts of holes all over the place when the warhead goes off. A 20mm is far more likely to cause serious damage than the 0.50. The rates of fire were similar (RAF Hispano II) and the balistics were pretty close as well so they don't really factor into the equation.

Also the USAAF never had reliable 20mm it was not really an option. They went through at least 4 versions before ending up with the Colt version around 1958 or so. I can't find any discussion as why the P-38 did not swap out the 20mm for a .50. But in the East many B-25's were converted and then an actual standard version with a hard nose and 8x .50 plus 4 on the sides was created. Again probably because the .50 was plentiful and got the job done.

I agree that the US didn't ahve a reliable 20mm until the closing days of the war but disagree with the statement about not having a reliable gun until 1958. The post war 20mm guns fiitted to the USN aircraft were copies of the UK Hispano II and Hispano V both of which saw significant service and were perfectly reliable. These weapons on the USN aircraft could of course have been used in USAAF aircraft.

As I said before simply looking at only technical specs is of no consequence. In war you fight with what you have and modify/invent as needed.

Also in the Eastern theater the USAF quickly added semi armor piercing incendiary rounds to ignite the unarmored Japanese fuel tanks which appears to have been extremely effective. In this case 20mm discussion is moot as the .50 was sufficient.

In which case you have to ask yourself why the USN were so keen to have 20mm guns on their aircraft

 

[Shortround6]

EVERY Air Force in the world wanted multiple 20mm cannon or larger by the end of WWII except the US Air Force, and the US had spent an awful lot of money on "improved" .50 cal rounds, .60 cal rounds 20mm rounds, .90 cal rounds and guns to go with them. during WW II and leading up to Korea. So wanting and getting are not the same thing.

Experimental .50 cal guns after the M2 .50 cal.

T21
T22
T22E1
T22E2
T22E3
T22E4
T22E5
T22E6
T25
T25E1
T25E2
T25E3, standardized as the M3 .50cal gun
T26
T27
T27E1
T27E2
T27E3
T27E4
T27E5
T27E6
T27E7
T28
T34
T35
T36, Standardized as the M2A1 but production cut short by development of the T25E3/M3.
T38
There were others but were specialized AA or tank guns.

.60 cal guns:

Bendix 15mm machine gun
T17, A project to convert the German MG 151 to one of the American .60 cal cartridges.
T17E1
T17E2
T17E3
T17E4
T17E5
Hispano-Suiza caliber.60 T18 machine Gun
T18E1
T19
T31
T39, a T17E3 with an electric bolt head.
T41
T45, a Gatling type gun, weight 427lbs.
T46
T47
T49
T50
T50E1
T58
T59
T59E1
T62, another Gatling gun
T63
T64
T130, a revolver gun
T130E1
15mm T154, used a different type of ammunition.

20mm guns in another post. There are about 38 different versions/guns before getting to the FIRST revolver gun or Gatling. SOme guns were supposed to fire special 3500fps MV ammo.

 

[tomo pauk]

...

A related fact is the Germans said it took 26x20mm shells to bring down a B-17 while only 3x 30mm (all averages). So their choice was to develop a 30mm they could put on anything at the cost of very low MV. I do not remember ever reading of a large change in bomber loss rates when this put into service. So merely comparing round energy seems to be unrelated to effectiveness in combat. There must be other factors that were more important.

The wide scale introduction of MK 108 coincided with introduction of long range escort for USAF heavy bombers. A plane that carries 4 x 20mm will more likely shot down the bomber than a plane that carries 30mm, but happens to be shot down before it can put the B-17 on the sights.

And back to 'alot more damage' I disagree from the combat result for the fighters that used 4 (or even 2) 20mm. The results were around the same. Germans were known to shoot down 5+ planes a day with the FW-190 but not with the ME-109. The USAAF had about the same success with the 6 or 8 .50 cal setup. They did it with different damage types. The explosive shells tend to shred lightweight parts over a larger area. The .50 cal damage hard parts, (engine props, etc.) when they actually hit them. So it s trade of similar hit probability vs end affect.

The USAF was against far flimsier planes than LW or Japanese, so the direct comparison of armament based just on aircraft destroyed is not realistic.

Also the USAAF never had reliable 20mm it was not really an option. They went through at least 4 versions before ending up with the Colt version around 1958 or so. I can't find any discussion as why the P-38 did not swap out the 20mm for a .50. But in the East many B-25's were converted and then an actual standard version with a hard nose and 8x .50 plus 4 on the sides was created. Again probably because the .50 was plentiful and got the job done.

Other people have covered the US 20mm problematics. For Pacific in ww2: the .50 was there, was reliable and available in huge quantity, when mounted in sizeable batteries was devastating vs. anything lighter than small ship. The effects of gun's weight were purely academic once it was paired with powerful engines (but not before).

As I said before simply looking at only technical specs is of no consequence. In war you fight with what you have and modify/invent as needed.

Indeed, one the quantity was a quality on it's own, and many war machines were modified to suit better to the needs.
'Invent as needed' is not something I'd agree; Germans needed proximity fuses for their heavy Flak from the time Bismarck was sunk, yet it was not until the end of the war before they started the experiments.

 

[zjtins]

I will repeat the .50 was good and successful during WWII vs 20mm. IF anyone wants to extend that beyond what I said that we need a new topic.
The 20mm was unreliable to the US as defined by the continued use of the 6x.50 setup until Vietnam as front line fighter main armament. Yes there were many choices investigated, models, experimental guns and aircraft (and rocket or missiles) and other stuff. But they were not the primary system in use in US Air combat until Vietnam.
So all the history off weapon development and technical data is moot when you look at the actual use and combat effectiveness.
If 4x 20mm vs 6 x .50 was such and overpower massive difference then the US(AAF) either screwed up so bad for over 20 years then you all know better than the people who were then in charge or it was not enough difference at that time to persue. I chose the later.

On this we will have to disagree. A 0.50 bullet is normally going to knock a small hole going in and a small hole going out. If it hits something then there is a good chance that the object will be seriously damaged or destroyed. A 20mm is going to cause a hole going in and all sorts of holes all over the place when the warhead goes off. A 20mm is far more likely to cause serious damage than the 0.50.

That is a generalization not born out by combat. Numerous B-17s and P47's came back with severe 20mm damage and flew home. Shredding the skin basically doe snot bring plane down, a critical system or several less critical systems must be damaged/destroyed. The 20mm could not destroy an engine in one shot a .50 cal can, same with armor plate (typically). Any system hit by a .50 is at least severely damaged is had too much penetration. I have seen many gun cameras of many German fighters using 20mm and the plane they shot would at first lose sheet metal. It generally took a several shots before they finally found a soft spot to damage the plane enough to down it. When gun camera from US fighters were compared in the east once an SAPI round hit the fuel tank they always burned, a 20mm HE does not start fire like that. Against the Germans, IHMO the .50 cal fired until the engine quit, the pilot was killed, or the fuel tank flamed. Time on target is roughly the same so from that limited evidence the gun setups were equal.

Also when you read the biographies of US fighter pilots I do not ever remember hearing anyone state 6 or 8 .50 cal was not sufficient. On the contrary the guys flying the P-47 seem to universally acknowledge the value (firepower) of the 8x.50cal.

As far as every Air force wanting the 20mm, that is an unsupported claim not a fact never heard from anyone myself, and Russia went to 23mm or large because they only had 1-3 guns on a fighter had to deal with bombers.

Also the Russians used 1 20mm and 1 .50 (there 12.7 mm) on most of the production fighters in WWII. Again 4 20mm were no needed in there opinion. And I find it hard to believe if the .50 sucked so bad for country who found away to produce ungodly amounts of tanks, aircraft and trucks they would have made more 20mm cannons.

 

[Shortround6]

I will repeat the .50 was good and successful during WWII vs 20mm.
The 20mm was unreliable to the US as defined by the continued use of the 6x.50 setup until Vietnam as front line fighter main armament. Yes there were many choices investigated, models, experimental guns and aircraft (and rocket or missiles) and other stuff. But they were not the primary system in use in US Air combat until Vietnam.

This is getting down right laughable.

Only "combat results" count with you?
The FACT that the US NAVY STOPPED putting .50 cal guns in fighters back in 1947/48 and the US Air Force STOPPED putting .50 cal guns in fighters for US use in August of 1954 ( planes with .50s continued to be made for issue to allies for another two years)doesn't mean anything but cause we weren't in a shooting war at the time?

If 4x 20mm vs 6 x .50 was such and overpower massive difference then the US(AAF) either screwed up so bad for over 20 years then you all know better than the people who were then in charge or it was not enough difference at that time to persue. I chose the later.

It was actually 9-10 years, see above, see also the F-87, F-88, F-89, F-90, F-100, F-101, F-104, F-105 fighters, all in production well BEFORE the Viet Nam war started. In fact the Air Force was specifying SIX 20mm cannon on the bomber interceptors being worked on the late 40s Like the F-89. SO in part it was under 5 years.

As far as every Air force wanting the 20mm, that is an unsupported claim not a fact never heard from anyone myself, and Russia went to 23mm or large because they only had 1-3 guns on a fighter had to deal with bombers.

English may not be your first language but what I wrote was "Every nation wanted 20mm OR LARGER". Please show ANY nation that chose the .50 cal WHEN GIVEN A CHOICE after WW II.

Also the Russians used 1 20mm and 1 .50 (there 12.7 mm) on most of the production fighters in WWII. Again 4 20mm were no needed in there opinion. And I find it hard to believe if the .50 sucked so bad for country who found away to produce ungodly amounts of tanks, aircraft and trucks they would have made more 20mm cannons.

This is your unsupported opinion isn't it. The fact that the Russians had low powered engines had a choice between poor firepower and good performance and good firepower and poor performance had nothing to with it, right?
There were a number of small production batches with increased armament but the performance penalty was usually to big to get general acceptance. The LA-5/7 were an exception to the power problem but had a problem of their own.
While two 20mm guns would fit it seems that CG issues prevented (or weight performance issues) prevented the fitting of more guns. The third gun only showed up when a new lighter model gun showed up and the rounds per gun were cut to keep the gun/ammo weight about the same for the older two gun models and the 3 gun model. Post war 4 gun version had a new/ all metal fuselage and rather restricted ammo loads.
The Russians were big believers in fire power. For them to stick with 2-3 guns meant there had to be an overriding reason why the COULDN'T do it. And they did try under wing gun pods on some fighters.

That is a generalization not born out by combat. Numerous B-17s and P47's came back with severe 20mm damage and flew home. Shredding the skin basically doe snot bring plane down, a critical system or several less critical systems must be damaged/destroyed. The 20mm could not destroy an engine in one shot a .50 cal can, same with armor plate (typically). Any system hit by a .50 is at least severely damaged is had too much penetration. I have seen many gun cameras of many German fighters using 20mm and the plane they shot would at first lose sheet metal. It generally took a several shots before they finally found a soft spot to damage the plane enough to down it. When gun camera from US fighters were compared in the east once an SAPI round hit the fuel tank they always burned, a 20mm HE does not start fire like that. Against the Germans, IHMO the .50 cal fired until the engine quit, the pilot was killed, or the fuel tank flamed. Time on target is roughly the same so from that limited evidence the gun setups were equal.

OK, what part of "mixed belts" didn't you get. you are also trying to compare German 20mm hits with American/British 20mm hits. Belt feed guns seldom used the SAME ammo for the entire belt. Mixed belts were almost standard, A certain percentage of AP rounds and a certain percentage of HE rounds and/or a certain percentage of incendiary rounds. Tracers were somewhat optional. The mixes varied with time, theater and ammo availability. If you think that a single 46 gram .50 bullet will wreck and engine when a 128 gram AP 20mm round going about the same speed won't then I guess the laws of physics have been repealed. The British change fuses on their 20mm ammo fairly early in the war to stop detonation ON the skin. They also came up with a SAP/incendiary shell. They took a HE shell body, filled it with Incendiary material and screwed a hardened steel nose cap on instead of a fuse. This projectile would go through as much armor as a .50 cal AP round. If/when the shell body broke up it scattered the Incendiary material. It held 10 grams which is just about 10 times the amount in an American .50cal M8 API projectile. Since the M8 carried it's incendiary material in the nose between the jacket and the AP core it was stripped away before the core penetrated the armor.
AS for fuel tanks, A 20mm hit on a full or nearly full fuel tank would often split the seam/s of the tank, making the self sealing property rather useless.

Just to make sure we are comparing the same thing. the Muzzle energy of a .50 cal API round is about 17,800 joules. The muzzle energy of the MG 151/20 shells (of various type) was around 29,000 joules. The Muzzle energy of the 20mm Hispano rounds was 47-50,000 joules depending on shell and length of barrel.

Both the British and Americans shot up a bunch of old, derelict airframes on the ground in controlled tests to assess the damage done. So did the Germans.

No one bullet or projectile works 100% in all cases.

 

[tomo pauk]

Russians developed and used 23mm and 37mm for air-to-air fighting, along with air-to-ground role. It's hard to find out any bad word from them about the US 37mm in P-39s. They were also testing the 45mm cannon. A proof that they were far from satisfied from existing 20+12,7mm setups. The B-20 was the last of the 20mm, after the ww2 ended they quickly moved to 23-37mm weaponry.

http://www.ww2aircraft.net/forum/weapons-systems-tech/ussr-aircraft-weapons-13780-4.html#post389581

 

[Glider]

I will repeat the .50 was good and successful during WWII vs 20mm. IF anyone wants to extend that beyond what I said that we need a new topic.
The 20mm was unreliable to the US as defined by the continued use of the 6x.50 setup until Vietnam as front line fighter main armament. Yes there were many choices investigated, models, experimental guns and aircraft (and rocket or missiles) and other stuff. But they were not the primary system in use in US Air combat until Vietnam.

This is clearly wrong. I will not add to what others have posted. The reliability statement is also wrong for the USN aircraft fitted with copies of the British Hispano II and V

So all the history off weapon development and technical data is moot when you look at the actual use and combat effectiveness.
If 4x 20mm vs 6 x .50 was such and overpower massive difference then the US(AAF) either screwed up so bad for over 20 years then you all know better than the people who were then in charge or it was not enough difference at that time to persue. I chose the later.

No one is saying the USAAF screwed up, for the requirements they had in WW2 the 6/8 x 0.5 was good enough and did the job. Had they gone up against aircraft such as the B17 or IL2 then the problem would have magnified.

That is a generalization not born out by combat. Numerous B-17s and P47's came back with severe 20mm damage and flew home.

Actually it is borne out by combat. The IJAF believed that 4 x HMG was sufficient until they went up against heavy bombers and then they switched to 20mm as fast as they could. The Japanese HMG was a copy of the USAAF 0.5. The Lutwaffe also relied on cannon against heavy bombers. Every nation that went against heavy bombers went for cannon and left the HMG behind.

Shredding the skin basically doe snot bring plane down, a critical system or several less critical systems must be damaged/destroyed. The 20mm could not destroy an engine in one shot a .50 cal can, same with armor plate (typically). Any system hit by a .50 is at least severely damaged is had too much penetration.

I am sorry but this is wrong on so many counts. A 20mm would destroy an engine, it also has much better armour penetration and the explosive warhead significanly increases the chances of hitting key systems. As mentioned on the previous posting a 0.5 is likely to leave two holes behind one going in and one going out. Inside a WW2 aircraft in particular bombers there are loads of places where there is nothing critical

I have seen many gun cameras of many German fighters using 20mm and the plane they shot would at first lose sheet metal. It generally took a several shots before they finally found a soft spot to damage the plane enough to down it.

You see sheet metal as its pushed outwards by the exploading warhead, the slipstream gets itt and its pulled off. You don't see on a camera film the damage being done insde the aircraft.

When gun camera from US fighters were compared in the east once an SAPI round hit the fuel tank they always burned, a 20mm HE does not start fire like that.

Do you think they would show gun film of aircraft that got away? and yes a 20mm would do far more damage than a 0.50

Also when you read the biographies of US fighter pilots I do not ever remember hearing anyone state 6 or 8 .50 cal was not sufficient. On the contrary the guys flying the P-47 seem to universally acknowledge the value (firepower) of the 8x.50cal.

As mentioned before for the USAAF the 0.50 was good enough. You clearly believe that it was at least the equal of the 4 x 20mm in which case you need to ask yourself why did the USN want to use the 20mm?

As far as every Air force wanting the 20mm, that is an unsupported claim not a fact never heard from anyone myself, and Russia went to 23mm or large because they only had 1-3 guns on a fighter had to deal with bombers.

All airforces British, Italian, Japanese, French, Russian went to 20mm during the war, only the USAAF stated with the 0.50 out of choice. You should also remember that the Russian 12.7 HMG was a much better weapon than the USA 0.5 and they went to 20mm. It is a very supported claim.

Also the Russians used 1 20mm and 1 .50 (there 12.7 mm) on most of the production fighters in WWII. Again 4 20mm were no needed in there opinion. And I find it hard to believe if the .50 sucked so bad for country who found away to produce ungodly amounts of tanks, aircraft and trucks they would have made more 20mm cannons.

In the Russian opinion the 20mm was needed and the LA5 and LA 7 were armed with 2 or 3 of them

 

[Aozora]

Damage done by 20mm MG-FF - enough to write off a Spitfire:

Note: Large entry holes in port fuselage skin, exploded inside, wrecking structure, shrapnel exit holes starboard. Please find a photo showing .50 cal HE doing as much damage. (Price: The Spitfire Story, 2010 page 100)

Also: The "argument" about the USN finding the 20mm against Kamikaze attack was ineffective is a red herring - the USN wanted a weapon which would obliterate such an aircraft, because, even though the 20mm strikes were causing heavy damage and effectively shooting down the attacker, they were not enough to deflect an attacker determined to crash and explode, nor did it stop large parts of destroyed aircraft hitting the ship and still causing damage. The 40mm was obviously more effective, but the USN ultimately went for a fully automatic 3" weapon (Mk 22 40-50 rounds per minute) which was able to destroy an aircraft with one hit.

 

[Glider]

Good photo, It looks like four hits and the aircraft is written off. Also notice that the top of the fuselage above the rear shell hole is wrinkled, which is often an indicator that the internal damage broke the back of the Spitfire.

No 0.5 bullet would cause such damage.

 

[zjtins]

[In 'Guns of the Royal Air Force 1939-1945' by G.F. Wallace - who was there - there is an account of British tests of the British and US Hispanos which took place early in 1942. The British were unhappy with initial supplies of the American-made guns: "there were frequent misfeeds and lightly struck cap stoppages, and the life of several small components was very short" so a comparative test between one British and three American guns was set up. The intention was to fire 5,000 rounds from each gun without replacing any components. "The British gun fired the full programme but the performance of the American guns was so bad that in each case the trial had to be abandoned before the 5,000 rounds had been fired." The British gun experienced 19 stoppages in firing 5,012 rounds. The American guns experienced 67 stoppages out of 4,092, 97 out of 3,705 and 94 out of 2,610 respectively. Incidentally, Wallace states that the US guns were "beautifully made and better finished than our own" and expressed surprise that although lightly struck caps were a major source of stoppages, even more frequent were mis-feeds.]

from: Modifications and Attempts at Standardization

So yes they were unreliable.


Great... one picture!?!?

Actually why look for gun camera footage on youtube and make you own call about the .50 cal setup effectiveness. I simple cannot tell the difference between the .50 and a FW-190 setup in terms of time on target. They both basically destroy their fighter targets in the same time frame which is the limiting factor, for a pilot to point his guns at a maneuvering target and get rounds on it..

 

[zjtins]

This is getting down right laughable.

Only "combat results" count with you?
The FACT that the US NAVY STOPPED putting .50 cal guns in fighters back in 1947/48 and the US Air Force STOPPED putting .50 cal guns in fighters for US use in August of 1954 ( planes with .50s continued to be made for issue to allies for another two years)doesn't mean anything but cause we weren't in a shooting war at the time?

Right that's after 1944/45. And as I said they had unreliable 20mm until later.
If you guys stayed focused and stopped implying something on I did not say or at least read it all and stay on track, this would work better.

Again the .50 cal setups worked in WWII and after for Air Air combat. There was no driving factor to push the US to 20mm. The .50 cal worked and worked well. Again i have never seen a pilots reports ever talking about they wanted 20mm after running the .50 cal setup.
Other country's chose the 20mm for different reasons. They had different guns and different ammo. If you want to talk about Brits fuzed ammo the German minegeshoss results are out. If you want to talk about 3 gun setups on Russian fighters then you cant use the results from 1x 20mm (and 1 .50cal) gun setup which was the vast majority of combat on the eastern front.


Also with over 150,000 fighter aircraft and 4 million m2s built, the 130,000 20mm could only are P-38, P61 and a few trial aircraft.