# Yet another .50 vs 20mm thead.



## Shortround6 (Oct 20, 2012)

There seems to be quite a bit of confusion about the American .50 cal gun/ammo and its effectiveness and efficiency, which are not the same thing. 

The .50 cal Browning had a lot of things going for it and many good qualities, however many of these came with a price. 

Reliability = Heavy
Durable = Heavy
High velocity = Heavy

The Russian 12.7mm machine gun may have been reliable but it was not durable. The receiver and internal action parts had a life 1/2 to 1/4 that of the Browning. The German MG 131 was about 55% as powerful per round and could be lighter because of that. The Japanese and Italian 12.7mm machine guns were also much less powerful per round. These Axis rounds ( and the British .5 in) used lighter bullets at lower velocities. They could use shorter/lighter barrels and shorter, lighter receivers. Some of these guns could fire faster than the Browning ( and some synchronized much better) but they did not have the penetration power, the _smashing_ power of the American and Soviet 12.7mm guns and they had longer flight times which made deflection shooting harder or shorter ranged ( or both). 

The Japanese Navy and the Luftwaffe both used a rather low powered 20mm cannon at the start of the war. Measured by kinetic energy they were about 30% more powerful than the .50 but had the huge advantage of exploding shells. However the guns were slow firing, roughly 2/3rds the cycle rate of the .50 once the .50 got to 750-850rpm, had limited ammo capacity and fired their shells about 2/3rds as fast which again limits the effective range for air to air gunnery. They did weigh about the same, if not a bit lighter, than the .50 Browning though. 

Both the Japanese and the Germans introduced newer, more powerful 20mm guns but they gained weight. The Hispano started heavy (designed for durability) but was the most powerful of the common airborne 20mm guns of the war. 

Comparing the Hispano to the .50 cal _in the air to air role_ means forgetting a lot of the advantages of the .50 in the ground role. At 600yds at sea level the Hispano shell arrives about 1/10 of a second behind the .50 cal bullet. It takes the .50 cal about .7 seconds to cover the 600yds. At 1000yds the difference has grown to 4/10ths of a second. The .50 does have definite advantage over the Hispano (and every other WW II 20mm aircraft gun) but it doesn't show up vs the Hispano until you are on the fringes of practical air to air ranges, the advantage does show up at more moderate ranges vs the slower 20mm types. 

Much is made of the Americans _KEEPING_ the .50 cal not only for the war but till and through the Korean war, at least by the Air Force. That is true but it wasn't for want of trying. The number of projects for faster firing .50 cal guns ( finally bearing fruit in the spring/summer of 1945), higher velocity .50 cal guns ( using several different cartridge cases), .60 cal machine guns ( again with more than one cartridge) and 20mm guns number in the dozens. An awful lot of time, money and effort spent if the US was truly satisfied by the .50 cal Browning. Granted most of projects came to nothing (in part because of too ambitious goals) but does show that the US ordnance officials were not happy with the .50 cal.


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## fastmongrel (Oct 20, 2012)

Unfortunately the .50 v 20mm debate always goes the same way. Mostly US forumites defending the Good Old .50 against the ungodly hordes of cheese eating surrender monkey 20mm cannon. Along the way come claims about how Bombers were chopped in half, Tiger tanks were blown up and Destroyers were sunk by the mighty .50

The .50 was certainly proven to be adequate for the US but if the US had faced heavily armed bombers like other air forces did I believe the 4 or 6 x .50s would have been found similar to the 8 x .303 of the RAF in 1940 adequate but not quite good enough. Just because the US didnt have to face such foes is no excuse all armed forces should look to the worst case scenario and should equip themselves or have available the equipment for this task. The real villains of the peace were the people who were responsible for the shoddy design and manufacture of the US Hispano, if the US had needed the 20mm gun in a rush they would have been in a pickle till they could have got supplies of an adequate weapon. I still find it deeply shocking that the country who came up with so many brilliant easily made weapons could drop the ball so badly with the Hispano. I dont know if anyone went to prison for this debacle but someone should have been tried on charges of treason.

My take on the Browning v Hispano is the Berezin B-20 now that was how to build an aircraft cannon, as light as the Browning with approximately the same ROF and almost the Hispanos power.


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## ShVAK (Oct 20, 2012)

fastmongrel said:


> My take on the Browning v Hispano is the Berezin B-20 now that was how to build an aircraft cannon, as light as the Browning with approximately the same ROF and almost the Hispanos power.



And maybe half the longevity, as Shortround noted. That might've been fine for the VVS' purposes but I'd rather have a slightly heavier gun if it meant it didn't burn out in the middle of a dogfight.


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## fastmongrel (Oct 20, 2012)

ShVAK said:


> And maybe half the longevity, as Shortround noted. That might've been fine for the VVS' purposes but I'd rather have a slightly heavier gun if it meant it didn't burn out in the middle of a dogfight.



If the Hispano and Browning had a life of say 10,000 rds then a life of 5,000 rds is fine. How many aircraft guns wore out before the aircraft became a hole in the ground or the armourer pulled it out and replaced it. If the gun wore out during a flight then the armourer should have been reassigned to latrine duty.


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## Tante Ju (Oct 20, 2012)

Shortround6 said:


> There seems to be quite a bit of confusion about the American .50 cal gun/ammo and its effectiveness and efficiency, which are not the same thing.
> 
> The .50 cal Browning had a lot of things going for it and many good qualities, however many of these came with a price.
> 
> ...



Important for a ground weapon, unimportant for an air weapon. How much was the avarage belting for a .50 cal HB - 300 rounds? What was the loss rate for aircraft, like 5%? That means the gun is lost or destroyed statistically after 20 chances to fully empty its rounds. That's 6000 rounds fired, at best, and much, much less in practice. So why build such a gun that will not survive the aircraft anyway?

Durability of the internal mechanism does not tell much of the service needs of the gun. A gun firing far more powerful rounds will eat up the barrels quickly, and will need replacement more quickly. Worn barrels will degrade muzzle velocity and dispersion, so it would be interesting how did a typical Browning MV looked like after the barell fired 1000 rounds compared to the competetion, and what lifespan (no. of bullets fired before replacement) was claimed for the aircraft mounted version (not the HB version). I would risk a bet that the difference wasn't very great anymore.

For the American .50 cal heavy machine gun, the manual stated no more than 75 rounds to be fired in one burst, and that has to be followed _after one minute of cease firing by one 25 round burst per minute. The gun was to be cooled for at least 15 minutes before another long burst was attempted_. I am sure pilots and gunners were less concerned about that when enemy aircraft were around, but it was at the expense of exponentially increased wear on the barrel and internal parts, giving a proper context to those rather theoretical figures you quoted.



> The German MG 131 was about 55% as powerful per round and could be lighter because of that. The Japanese and Italian 12.7mm machine guns were also much less powerful per round. These Axis rounds ( and the British .5 in) used lighter bullets at lower velocities. They could use shorter/lighter barrels and shorter, lighter receivers. Some of these guns could fire faster than the Browning ( and some synchronized much better) but they did not have the penetration power, the _smashing_ power of the American and Soviet 12.7mm guns and they had longer flight times which made deflection shooting harder or shorter ranged ( or both).



"Smashing power" is an interesting concept. I guess it was created very recently to get something. Unfortunately such smashing power doesn't exist for aircraft - be it the Russian UBS, the German Mauser or the American Browning, they all just made roughly 13 mm holes in aluminium skin that was no more than 1 mm thick typical, and all could penetrate armor on aircraft reliably, pierce fuel tanks and radiators, "smash" radios and generators. It didn't not matter much in the air if the Browning could penetrate as much as (let's say) 25 mm of steel armor and the other only 15mm if all that was to be found on aircraft was 4-8mm.. That was all that was to be asked from an aircraft gun IMHO, and others seem to have correctly realized that anything else is an overkill and adds nothing of practical value, but results in a heavier gun.



> The Japanese Navy and the Luftwaffe both used a rather low powered 20mm cannon at the start of the war. Measured by kinetic energy they were about 30% more powerful than the .50 but had the huge advantage of exploding shells. However the guns were slow firing, roughly 2/3rds the cycle rate of the .50 once the .50 got to 750-850rpm, had limited ammo capacity and fired their shells about 2/3rds as fast which again limits the effective range for air to air gunnery. They did weigh about the same, if not a bit lighter, than the .50 Browning though.



When was the cyclic rate of the M2 Browning improved to 750-850? Shwak cannon production started in around 1936, Mauser MG 151/15 version in 1938... the Oerlikon FF goes back to WW1, but it was fitted to LW aircraft since 1937 on trials.



> Both the Japanese and the Germans introduced newer, more powerful 20mm guns but they gained weight. The Hispano started heavy (designed for durability) but was the most powerful of the common airborne 20mm guns of the war.



"Heavy" does not equal durability outside the US..  the Hispano in fact was very slim, what made it heavy was it's very long barrel made for it's powerful round. It's a distant relative to the Oerlikon cannons anyway (which existed if utterly powerful forms, though usually the 'compact' FF version was picked for aircraft by most and is best known).



> Comparing the Hispano to the .50 cal _in the air to air role_ means forgetting a lot of the advantages of the .50 in the ground role. At 600yds at sea level the Hispano shell arrives about 1/10 of a second behind the .50 cal bullet. It takes the .50 cal about .7 seconds to cover the 600yds. At 1000yds the difference has grown to 4/10ths of a second. The .50 does have definite advantage over the Hispano (and every other WW II 20mm aircraft gun) but it doesn't show up vs the Hispano until you are on the fringes of practical air to air ranges, the advantage does show up at more moderate ranges vs the slower 20mm types.



600 and 1000 yards are completely unrealistic for aircraft mounted guns for any kind of aimed fire. Not only it was humanly extremely difficult to even see much less aim at a target that far from an aircraft, but the dispersion of the gun was such that even with perfect aiming marginal number of hits would obtained anyway. Sure many rounds can be fired from many Brownings - by which time you are probably at the same weight and bulk as simply fitting a gun with truely impressive ballistic potential like the Mk 103.


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## Xjrtaz (Oct 20, 2012)

Now this is quite an interesting topic.
As far as the British .303, that is altogether another forum topic, all I can do is quote what my father stated about his experience with the armament on the Hurricane and Spitfire, compared to the .5's on his Thunderbolt.
My father is Witold `Lanny' Lanowski, Polish fighter pilot with a wealth of experience before he joined the 56th FG. he always said and I quote (baring in mind that you have to imagine a twang of a polish accent here) "bloody pop guns" He hated them with a passion, he prefered that they were situated side by side on the Hurricane giving you at least some concentrated firepower, but the Spit?...well, he detested it, so many faults, fataly proved by one Polish pilot to the Aero engineers from farnborough whilst stationed with 302 SQ at Northolt, one of them being fitted with a rifle caliber bullet, located spaced innefectually apart on the wings (not designed to carry weapons!!). The polish pilots zeroed thier 303's to 100yds as as my father said, "you needed to get right up the Niemcy's ass!" to hope to do any lasting and immediate damage.
When he flew Thunderbolts (and the Mustang with the 354th) he was overwhelmed by the destructive power of the .5. one of his combat reports states that a half second burst and the 190 disintegrated in front of him...!
I also remeber my father commenting on being fired at by 20mm cannons, he said it was a frightening experience if they hit you, but thier ROF was much slower then that the mg's that were also fitted to the German fighters
I hope this sheds some light from a fighter pilots point of view


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## CobberKane (Oct 20, 2012)

fastmongrel said:


> If the Hispano and Browning had a life of say 10,000 rds then a life of 5,000 rds is fine. How many aircraft guns wore out before the aircraft became a hole in the ground or the armourer pulled it out and replaced it. If the gun wore out during a flight then the armourer should have been reassigned to latrine duty.



All depends on the circumstances, I guess. No doubt the AVG were very happy to have the extended life of the Browning, given how long their supply ines were. The Soviet doctine of quantity over quality also makes sense, if you have secure supply lines to a large industrial base and pleny of manpower to expend. What was it Stalin said? "Quantity is its own quality."
I think its important to remembr that US fighters never really met anything bigger than medium bombers, and throughought the ETO escort role even those were really targets of opportunity. Bomber interception in the ETO, where most of the resources went, was a secondary consideration for American fighters; for most of the time the main job was to knock down single and twin engine fighters. For this purpose the .50 was effective, available and proven. Doubtless the USAAF recognised its limitations in roles beyiond that in which they were typically using it, and maybe by the time of Korea they should have gone the Navy way and got the cannon right, but it certainly got the job done during WWII.


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## wuzak (Oct 20, 2012)

Also, wasn't the 37mm cannon the USAAF's preferred weapon for bomber interceptors?

The XP-67 was designed as a long range bomber interceptor, and was to have 6 x 37mm cannon!


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## Shortround6 (Oct 20, 2012)

An Attempt to address some of the issues brought up. 

"My take on the Browning v Hispano is the Berezin B-20 now that was how to build an aircraft cannon, as light as the Browning with approximately the same ROF and almost the Hispanos power"

The Berezin B-20 didn't show up until some point in 1944 and wasn't in wide spread use until 1945 ( and wide spread was still a far cry from universal)

"If the Hispano and Browning had a life of say 10,000 rds then a life of 5,000 rds is fine."

It might have been fine but most of the Russian guns were closer to a 2500 round life. It suited the Russian style, it suited the Russian problem of low powered engines and it suited the Russian supply situation. Replacement guns did not have to come by ship and take weeks if not months to get to the front. 

I specifically said receivers and internal parts because barrels were a consumable item and were expected to be changed several times (at least) before the receiver and lock work wore out. This goes for most peoples aircraft guns. A decently equipped armourer would have a throat gauge or inspection tool and replace barrels before wear got to be too big a problem. Remote air fields and supply problems in a particular theater/time period obviously affect things. 

"Unfortunately such smashing power doesn't exist for aircraft...." 

Actually it does. Please find an aircraft that was of "pure" monocoque construction. Despite descriptions saying an aircraft was of monocoque construction just about all aircraft were of semi-monocoque construction. They used spars and ribs in the wings and sometimes stringers, They used longerons, frames and/or bulkheads and stringers in the fuselage. They used motor mounts to fasten the engine to the airframe and used mounting plates or flanges at times for the motor mounts or wing to fuselage joints ( or tail planes). It was the ability of the large caliber weapons to break or seriously damage/degrade these structural components that caused aircraft to break up in the air. Granted it was a minority of the projectiles that hit an aircraft that hit structural components. It was also found that the Heavy Machine guns and cannon firing "ball" ammo (non-exploding) could, on occasions, split nearly full fuel tanks open along the seams rather than just punch holes in them. It depended on the size of the tank, the % of fuel in the tank, if the bullet hit well below the top of the fuel level or went over it and so on but the effect was there and could not be accomplished in aircraft sized fuel tanks with rifle caliber machine guns. 

I am not sure what phrase or word describes splitting open fuel tanks, breaking engine mounts, or causing wing spars/wing to fuselage joints to fail but "smashing power" works for me. Against the .50 is the fact that the British 20mm Hispano "ball" round was even better at these things. 

"When was the cyclic rate of the M2 Browning improved to 750-850? Shwak cannon production started in around 1936, Mauser MG 151/15 version in 1938... the Oerlikon FF goes back to WW1, but it was fitted to LW aircraft since 1937 on trials."

The M2 Browning was upgraded in 1940. I don't know if existing guns could be upgraded with new parts or not. The 1945 switch to the 1200rpm M3 required new guns, M2s could not be retro fitted. If the Germans were really in production of the MG 151/15 in 1938 it sure took them a long time to fit them to service aircraft in large numbers. I know they were used in the Spanish civil war in trial quantities (less than a dozen?) They don't seem to reappear until 1940, again in small quantities and finally make it into a fighter at the end of 1940/beginning of 1941. The Oerlikon FF does _NOT_ go back to WW I. It can trace it's ancestry back to WW I which is a bit different. The WW I Becker cannon used somewhat less powerful ammunition, was heavier, and fired at around 300rpm. It was developed into the Oerlikon F which was developed into the Oerlikon FF. 

I am trying for the balanced look and in many other threads I have been critical of the .50 Browning. It is certainly not the supergun that many make it out to be but it is also one of the 3 most powerful commonly used machine guns in WW II ( this depends on how you class the MG 151/15) and it's margin of power over over the German 13mm and Japanese/Italian 12.7 was substantial. It's time of flight offered an advantage over some of the lower powered 20mm guns in terms of hit potential as did it's higher rate of fire. Those are facts that cannot be wished away. On the other hand the .50 offered no practical advantage in time of flight compared to the Hispano over normal air to air ranges, and some of the later axis 20mm guns, the Soviet 20mm guns and the last Hispanos gave it a run for it's money in terms of rate of fire.


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## CobberKane (Oct 20, 2012)

Gidday, Wuzak - watch the game? You almost had me eating crow over those radial engines...

One other thing we can thank the .50s for is the camera footage they left us. None of this 'two hits and he's aluminium dust' crap you get with Hawker Tempest footage; lots of little flashes, bits falling off, pilot bailing - way more cool!


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## Shortround6 (Oct 20, 2012)

wuzak said:


> Also, wasn't the 37mm cannon the USAAF's preferred weapon for bomber interceptors?
> 
> The XP-67 was designed as a long range bomber interceptor, and was to have 6 x 37mm cannon!



The US had some rather bizarre notions as to what constituted bomber interceptor armament. Of course having built the XB-15, The XB-19, working on the B-29 and "The USAAC opened up a design competition for the very long-range bomber on 11 April 1941" and placing the contract for 100 B-36s on 23 July 1943 maybe they had an idea of what it would take to shoot down truly big bombers? 

I like the XP-54 with two 37mm and two .50 cals with the .50 cal guns fixed but the 37mm in a tilting nose section so that they could get common points of impact at different ranges


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## wuzak (Oct 20, 2012)

CobberKane said:


> Gidday, Wuzak - watch the game? You almost had me eating crow over those radial engines...



No, I did not.


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## CobberKane (Oct 21, 2012)

wuzak said:


> No, I did not.


 
19 all at full time. All Blacks took a penalty scrum afte the whistle and played on for five more minute before finally missing a dop goal


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## davparlr (Oct 21, 2012)

CobberKane said:


> Doubtless the USAAF recognised its limitations in roles beyiond that in which they were typically using it, and maybe by the time of Korea they should have gone the Navy way and got the cannon right, but it certainly got the job done during WWII.


At the time of the Korean War the Navy F9F was using four slow firing and apparently problematic M-3 Cannon whereas the AF F-86 was using six very fast firing M-3 machine guns. My analysis on probability of hit verses effectiveness of projectile indicated that, for two to three second burst, both packages are comparable in effectiveness, with the F9F having an advantage at long ranges but the F-86 was more effective at closer combat.

According to wikipedia (?) the Navy continued to have problems with its 20mm cannons through Vietnam. However, for early 50's, the AF got the better gun when they upgraded the M-3 machine guns on the F-86H, and on, to the vastly superior (as compared to the .50s), and faster firing, M-39 cannon.


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## gjs238 (Oct 22, 2012)

What do the P-38 pilots say about it?
When/how did they use the 20mm vs the .50?
What results were achieved?


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## gjs238 (Oct 22, 2012)

The 20MM was installed on a US heavy bomber.
Don't know how often this was done.
I think it was an unofficial field mod.
I remember reading about vibration/mount issues.


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## VBF-13 (Oct 22, 2012)

Xjrtaz said:


> The polish pilots zeroed thier 303's to 100yds as as my father said, "you needed to get right up the Niemcy's ass!" to hope to do any lasting and immediate damage.


That's the shortest I think I've ever heard. Your Dad was right, that's close company. I could be mistaken about this, but I believe my Dad's Hellcat was zeroed at 300 yards. 



Xjrtaz said:


> When he flew Thunderbolts (and the Mustang with the 354th) he was overwhelmed by the destructive power of the .5. one of his combat reports states that a half second burst and the 190 disintegrated in front of him...!


I can definitely believe that.


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## oldcrowcv63 (Oct 22, 2012)

Didn't the Geneva Convention "outlaw" or in some fashion proscribe the quad 0.50" as an inhumane weapon? I have to wonder just how _humane_ would be a quad 20 mm.


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## davparlr (Oct 22, 2012)

Xjrtaz said:


> The polish pilots zeroed thier 303's to 100yds as as my father said, "you needed to get right up the Niemcy's ass!" to hope to do any lasting and immediate damage.
> When he flew Thunderbolts (and the Mustang with the 354th) he was overwhelmed by the destructive power of the .5. one of his combat reports states that a half second burst and the 190 disintegrated in front of him...!


 
At 100 yds it is probably hard to miss. A half second focused burst from a P-47, about 40 or so rounds, at a hundred yards, would have a devastating effect on any airframe.


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## CobberKane (Oct 22, 2012)

gjs238 said:


> What do the P-38 pilots say about it?
> When/how did they use the 20mm vs the .50?
> What results were achieved?


 
That's a good question. I suspect the ballistics of the Hispano were less dissimilar to an HMG than was the case with the heavier cannon used on some other types. I don't think the 37mm on the P39 had too many fans amongst US pilots; I read a few accounts of them preferring the P400, or just not using the 37mm even when it was avaialable.


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## davebender (Oct 22, 2012)

Hs.404 cannon may have been durable but it wasn't known for reliability during combat.


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## Shortround6 (Oct 22, 2012)

davebender said:


> Hs.404 cannon may have been durable but it wasn't known for reliability during combat.



That may be hard to judge. We have the figures for the .50 cal machine gun, which had a fair share of trouble in some early installations, But figures for a number of other guns seem to hard to come by. We know that British Hispanos had a lot pf trouble in early Spitfires but does anybody have figures for the Hurricane II, Whirlwind, Beaufighter at about the same time? 

What was the mean time between failures or malfuctions for other 20mm cannon ?


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## buffnut453 (Oct 23, 2012)

By "some early installations" you mean pretty much every fighter installation thru late 1942. We often forget, given the 50 cal's outstanding performance in later P-47s, F4Us, F6Fs and P-51Ds, that the gun had major issues as installed in the F4F, P-40, Buffalo and P-51B that continued throughout most of 1942.


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## CobberKane (Oct 23, 2012)

Shortround6 said:


> That may be hard to judge. We have the figures for the .50 cal machine gun, which had a fair share of trouble in some early installations, But figures for a number of other guns seem to hard to come by. We know that British Hispanos had a lot pf trouble in early Spitfires but does anybody have figures for the Hurricane II, Whirlwind, Beaufighter at about the same time?
> 
> What was the mean time between failures or malfuctions for other 20mm cannon ?


 
From memory, there is an exhibit in the RNZAF museum that states the Hispano averaged one stoppage per 600 rounds, but this increase significanlt in dusty conditions


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## Jabberwocky (Oct 23, 2012)

CobberKane said:


> From memory, there is an exhibit in the RNZAF museum that states the Hispano averaged one stoppage per 600 rounds, but this increase significanlt in dusty conditions



Average stoppage rates for Hispano cannon varied wildly with local conditions, aircraft types and installation and feed mechanism used. 

2TAF stoppage rates for 1944/1945 were about 1 every 1560 rounds, with about 50% of stoppages due to belting/feed mechanism problems. Fighter Command stoppage rates in 1942 and 1943 were about 1 in 1800-2000 rounds, thanks mostly to the better servicing facilities and less dust in the mechanisms. I've also seen references to Hispano stoppage rates in the UK of about 1 per 3000, but no indication of what aircraft or what period. 

Stoppage rates were generally highest in early Spitfire Mk Vs, particularly with the 60 round drum magazine and before several gun heating mods were made. The Mk IX onwards had much better cannon reliability. Beaufighter and Mosquito armaments were also reputedly quite reliable. One RAAF crew sped their Hispano Mk IIs on a Beaufighter up to 1000-1100 rpm with no ill effects reported.

The RAAF found stoppage rates that were ridiculously high (more than 1 in 250 rounds if I remember _Darwin Spitfires_ correctly) when fighting over Darwin. A combination of the dry, dusty conditions and very high altitudes of combat, along with poor ammunition and incorrectly installed (or non-existant) cannon heating due to the hodepodge of Spitfires they got. The Austin feed mechanisms - which were badly bodged when the company took over some work from Molins - were also heavily to blame. The British Small Arms feeds were also horrible, and Molins ended up doing a re-design the feed mechanism (shaving five pounds of the original wight in the process).

The RAF also had problems with stoppage rates in Malta as well. Again, ammunition was a problem, along with dust. One account has toilet paper being laid over the breech mechanism to keep it from collecting dust while Spitfires were taxiiing on dirt runways. 

The Hispano Mk V was reportedly more reliable than the Mk II. I think the Mk V went with a new feed mechanism (maybe another Molins design) that helped sort some of the problems out. The life of most of the smaller parts in a Hispano Mk V was only 2500-3000 rounds, so this would be roughly the upper limit for stoppage rates, I'd suggest.


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## tomo pauk (Oct 23, 2012)

Thanks, not an everyday stuff to read about.


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## davebender (Oct 23, 2012)

The U.S.A.F. Armaments Laboratory concluded the Hs.404 cannon wasn't very reliable. I'm not going to dispute their expert opinion.


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## wuzak (Oct 23, 2012)

davebender said:


> The U.S.A.F. Armaments Laboratory concluded the Hs.404 cannon wasn't very reliable. I'm not going to dispute their expert opinion.



But was that he British built one or the US manufactured one?

I think there is little doubt that the US manufactured Hispano was less reliable than the British built one.


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## Jabberwocky (Oct 23, 2012)

wuzak said:


> But was that he British built one or the US manufactured one?
> 
> I think there is little doubt that the US manufactured Hispano was less reliable than the British built one.



US Hispano reliability was anywhere from 1/3rd to 1/8th of Hispanos of UK manufacture. Early ground tests saw the reliability as low as 1 stoppage every 30-60 rounds. 

The major problems were the chamber length being 1/16th of an inch too long, resulting in lightly struck percussion caps, and belt mis-feeds. 

By 1944 the US Hispano was experiencing 1 stoppage every 505 rounds in the P-38's nose mount (8th AF, in combat). By the end of the year reliability was about the same as in the RAF - roughly 1 stoppage every 1600 rounds. I believe this was mostly because of the lower altitudes combat was taking place at through the second half of the year.


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## CobberKane (Oct 23, 2012)

Jabberwocky said:


> US Hispano reliability was anywhere from 1/3rd to 1/8th of Hispanos of UK manufacture. Early ground tests saw the reliability as low as 1 stoppage every 30-60 rounds.
> 
> The major problems were the chamber length being 1/16th of an inch too long, resulting in lightly struck percussion caps, and belt mis-feeds.
> 
> By 1944 the US Hispano was experiencing 1 stoppage every 505 rounds in the P-38's nose mount (8th AF, in combat). By the end of the year reliability was about the same as in the RAF - roughly 1 stoppage every 1600 rounds. I believe this was mostly because of the lower altitudes combat was taking place at through the second half of the year.


 
Both your posts make me wonder whether the RNZAF were using US or UK Hispanos and under what condidtions (though I believe the Kiwis did most of their work in places like PNG and the pacific - pretty basic). Come to think of it, I can't think of a single RNZAF aircraft that use cannon anyway. Don't take too much from museum exhibits, I suppose


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## Jabberwocky (Oct 24, 2012)

CobberKane said:


> Both your posts make me wonder whether the RNZAF were using US or UK Hispanos and under what condidtions (though I believe the Kiwis did most of their work in places like PNG and the pacific - pretty basic). Come to think of it, I can't think of a single RNZAF aircraft that use cannon anyway. Don't take too much from museum exhibits, I suppose


 
RNZAF aircraft in the Pacific were almost exclusively US supplied.

However, there were six New Zealand squadrons in service in Europe and the Middle East with various commands (RAF and Coastal Command), and they operated a mix of Beaufighters and Mosquitos. 

The cannon installation in the early Beaufighters was pretty prone to stoppages, probably because it used the 60 round drum magazines. Fortunately, the navigator could be called on to clear jams, as the cannon were accessible from the cockpit. He was also responsible for reloading the cannon in flight, which I can't imagine would have been pleasant. 

Later the Beaufighter got belt feed for the cannon, complete with a foot operated pneumatic cocking device.


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## CobberKane (Oct 24, 2012)

Jabberwocky said:


> RNZAF aircraft in the Pacific were almost exclusively US supplied.
> 
> However, there were six New Zealand squadrons in service in Europe and the Middle East with various commands (RAF and Coastal Command), and they operated a mix of Beaufighters and Mosquitos.
> 
> ...


 
New Zealand squadrons also flew Tempests, and I think Typhoons, in the ETO. But yes, all the aircraft that bore the NZ insignia were in the PTO I believe and sourced from the USA; Buffalos and P40s and Hudsons to start with, then Corsairs later.
Interstinggly, I believe the first aiar to air kill of the RNZAF was scored by a gunner in a Hudson. He was Moari, which maybe gives some indication on how far ahead of the curve New Zealand was in terms of racial inclusiveness at the time.


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## fastmongrel (Oct 24, 2012)

CobberKane said:


> He was Moari, which maybe gives some indication on how far ahead of the curve New Zealand was in terms of racial inclusiveness at the time.



I think George Nepia might have had something to say about that. NZ was ahead of the curve but not by much.


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## CobberKane (Oct 24, 2012)

fastmongrel said:


> I think George Nepia might have had something to say about that. NZ was ahead of the curve but not by much.



By a lot, I think - compared to the situations in the USA and Australia at the time - but still with a hell of a lot of work to do, for sure. 
Incientally, I coudn't find the reference to the kill when i looked for it again, so don't take it as gospel.


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## Glider (Oct 25, 2012)

Jabberwocky said:


> The RAF also had problems with stoppage rates in Malta as well. Again, ammunition was a problem, along with dust. One account has toilet paper being laid over the breech mechanism to keep it from collecting dust while Spitfires were taxiiing on dirt runways.



In The Spitfire Year 1942 which recounts the fighting over Malta, they did have stoppage problems with the 20mm but it was traced to US manufactured ammunition. Despite the serious shortages on Malta they destroyed all the US ammunition and the problem stopped


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## Edgar Brooks (Oct 25, 2012)

As so often, fighter pilots were completely in the dark, when it came to decisions made by the Air Ministry; today, it tends to be forgotten that the RAF always had to consider the possibility of a continuation of the Battle of Britain, with its concentration on killing bombers, not just fighters. The following is a matter of records, so, please, curb any tendency to leap up and down, crying, "That's rot." (or worse.)
It was found that the .5" was no better at penetrating German bomber armour than the .303", and, with the average pilot unable to properly master the art of deflection shooting, it was decided that four fast-firing .303" guns were more likely to fatally hit (or at least immobilise) the crew, from the side, than a pair of slower-firing .5". The 20mm was also considered essential, if, as feared, Germany produced bigger, more capable, and better-armoured, bombers. I'm not sure where the idea, that a Spitfire wing was not designed to carry 4 x .303" Brownings, comes from, since it was always designed with that armament, with the elliptical shape ensuring that the guns could be fitted into such a slim wing.
The .5" armament, in U.S. aircraft, made more sense, since their opponents were, most often, fighters, not bombers.
The 20mm was already being planned for (and tested) before the war started, but ammunition feed troubles bedevilled the system; at least five companies tried to come up with a workable system, with Chatellerault just edging out Molins (who were instrumental with the Mosquito "Tsetse.") Eventually the Vc was capable of doing what the Air Ministry wanted.
Leigh-Mallory did his utmost to get the .5" accepted, but was continually told to "push off" by the Air Ministry, until (and it's a major moment) the gyro gunsight made its appearance in 1944; almost overnight, average pilots could hit their targets, so the Ministry finally relented, and allowed the .5" to be fitted into Spitfire IXs, XIVs, and (post-war) XVIIIs (almost too late, since the soon-to-arrive 21, and Tempest, used 4 x 20mm cannon, and no machine guns at all.)
Edgar


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## Shortround6 (Oct 25, 2012)

To add to this the .50 cal gun/s and ammo tested by the British in the 1930s were not the .50 cal guns and ammo of 1942 or of 1944. And the guns/ammo of the Korean war were yet again different. 

The 1930s guns fired at 600rpm (at best) and were down to 400-500rpm when synchronized. The ammo used a slightly heavier bullet ( enough to win bar bets but that is about it) but operated at a lower pressure and had a velocity closer to 2500fps than 2900fps. I am not sure when the high velocity AP rounds showed up. The long pointy nose that helped the bullet retain velocity very well also meant that it tipped easier when penetrating aircraft skin and so it had a greater tendency to it interior barriers (like internal armor) sideways which hurt penetration. The 1942 belts were about 40% AP, 40% incendiary and 20% tracer fired from the 750-850rpm guns (which came in at some point in 1940). The 1944 belts were 90-100% M8 API ammo. 

The British changed the ammo types used in the .303 guns too. BoB used about 3 guns firing ball ammo. Two with AP, two with MK IV incendiary tracer and just one with the MK VI (De Wilde) ammo. Later on there were different mixes for different uses and for different aircraft. As the De Wilde became more available it was used in ever increasing amounts. Ball ammo disappeared soon after the BoB.


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## tomo pauk (Oct 25, 2012)

Those .5" guns/ammo: was it the Vickers type, or Browning?


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## Shortround6 (Oct 25, 2012)

It was the Browning. The .50 cal Browning dates back to the early 20s (work started _during WW I)_. Powder and ballistics of a number cartridges improved during that time. By 1938 or so the American 30-06 could move a bullet (150 grains) as fast using 42,000lbs chamber pressure as it took 50,000lbs pressure in 1906. That is peak pressure, the longer burning "newer" powder/s had a bigger area under the pressure curve even if the peak was lower. move the peak back up and you could use heavier bullets or get more velocity.


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## fastmongrel (Oct 25, 2012)

Did the Air Ministry test any other 0.5" guns I am thinking particulary of the FN 13.2 it seems to have been lighter, fired HE round with more explosive and had a higher ROF. Though thems internet facts and not to be taken as 100% true


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## tomo pauk (Oct 25, 2012)

I have another question:
Were the technicians of the Air Ministry firing the guns directly at the different armor specimens, or were the incoming bullets 1st made to pierce the sheet aluminium inclined at some angle vs. the bullets?


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## Edgar Brooks (Oct 25, 2012)

They did both (at least.) Shots were fired at hulks, sheet metal, armour (not just German,) from different ranges and different directions. It was found, for instance, that even the .5" could be deflected by the taper of the fuselage, if fired from directly behind, and, in the Fw190, the (retracted) tail wheel gave added protection (plus all of the "furniture" behind the pilot's seat,) even before it reached the armour.
I've found nothing, so far, about guns, which could not be made here, being tested, but it begs the question, what would be the point, if they couldn't be used?
The "de Wilde" ammunition was a red herring, since it was not used; the name was used as a cover for a newer, better incendiary type of ammunition, invented here.
Tracer was rarely used, since the sparkle of the incendiaries was found to be most useful for gauging when hits were being achieved; at night it destroyed night vision but had to be used in bombers to give gunners a visual clue. When "Village Inn" came into use, right at the end of the war, it wasn't needed, any more, for the bombers.
The .5" was 12" longer than the .303", so could not have been fitted as a one-for-one replacement; in the Spitfire the outermost compartment cover had to be bulged, slightly, to accommodate the rear of the body of the .303".
Always bear in mind that it was thought unlikely that single-engined, high-speed fighters would be encountered over the U.K; Sholto-Douglas held out against fitting armour behind the Spitfire pilot, because he said that it was the fastest thing in the air, so nothing would be able to get behind it, unless the pilot made a mess of it.
Edgar


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## Jabberwocky (Oct 25, 2012)

I’ve read that US 20mm ammunition was problematic in several sources, but none of them seem to mention why this was so. Anyone have any more on this?



As for the RAF comparative tests of the .303/.50/20mm. The 1939 tests were conducted against plain high hardness roll homogenous steel armour (IT 70) without any intervening barriers. The were done at 0, 20 and 40 degrees. 

There were other tests done against RAF bombers and crashed/captured Luftwaffe that tested penetration through intervening aircraft barriers, such as fuselage skinning and internal stringers. 

There were several different sets of tests carried out against 109 fuel tanks. 

The early tests found that these German self-sealing tanks (at least those found on the 109E) were vulnerable to pretty much everything fired at them, although most vulnerable to the 20 mm. Keep in mind that this is before deployment of API for the .50 cal, but tested with .303 API.

The early German self-sealing tanks had 5-15 mm of various types of rubber, with canvas/leather and aluminium layers. There was also a 8mm dural bulkhead (10 layers of 0.8 mm sheets) protecting the fuel tank for the 109E-4 onwards, which was somewhat haphazardly retrofitted to earlier production aircraft. 

Of course, WW2 in the air was a technology race and later tests on the tanks in the 109F and 109G come up with a different conclusion. The tanks were much better protected – in addition to a 16-24 mm laminated bulkhead (20-30 layers of .8 mm dural), there was generally a 15 mm lining and sometimes an additional 5mm layer covered in thin plywood. 

The tests found that these tanks were almost immune to the .303 and had much reduced vulnerability to .50 ammunition. The dural bulkhead was almost proof against penetration by .303 API beyond 150 meters or if there was any appreciable off angle or yaw.

Of course, there was a penalty: The weight of the 109’s fuel tank rose from 58 lbs in the late Es to 121 lbs in the F2/4. The dural plate weighed up to 66 lbs. Interestingly, there is a report on a captured 109G-14 where there was no self-sealing fuel tank, and no other armour, just a plywood box (!) for protection. 


Personally, I think the Air Ministry had the right idea in the .303 vs .50 cal stakes until about mid/late-1941, by which time armour protection had risen to such levels that the .303 was pretty inefficient and should have been phased out in favour of the .50.


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## CobberKane (Oct 26, 2012)

Glider said:


> In The Spitfire Year 1942 which recounts the fighting over Malta, they did have stoppage problems with the 20mm but it was traced to US manufactured ammunition. Despite the serious shortages on Malta they destroyed all the US ammunition and the problem stopped


 
What was it with American manufacturing and the 20mm? They seemed to do everthing else great. Question for the factory managers: those guys on the production line, the blue-eyed blonde ones who were alway humming 'duetschland uber alles' while they worked - did you ever wonder if maybe...


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## Shortround6 (Oct 26, 2012)

It had very little to do with the people on the production line and lot to do with the people setting the "standards". Certain dimensions were changed or tolerances allowed. The 20mm fell into the "cannon" category of ordnance which was allowed looser tolerances than "small arms" like machine guns.


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## Glider (Oct 26, 2012)

CobberKane said:


> What was it with American manufacturing and the 20mm? They seemed to do everthing else great. Question for the factory managers: those guys on the production line, the blue-eyed blonde ones who were alway humming 'duetschland uber alles' while they worked - did you ever wonder if maybe...



My best guess is that money was behind it.


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## Glider (Oct 26, 2012)

Shortround6 said:


> It had very little to do with the people on the production line and lot to do with the people setting the "standards". Certain dimensions were changed or tolerances allowed. The 20mm fell into the "cannon" category of ordnance which was allowed looser tolerances than "small arms" like machine guns.



That may be the official reason but at the end of the day the wretched things didn't work. They knew what changes needed to be made as the UK had been through this learning experience and were almost begging them to make the changes.
Aso the changes that were needed had nothing to do with tolerances, there were some basic design changes such as the size of the breach. It also doesn't explain the problems with the ammo.


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## Shortround6 (Oct 26, 2012)

Glider said:


> That may be the official reason but at the end of the day the wretched things didn't work. They knew what changes needed to be made as the UK had been through this learning experience and were almost begging them to make the changes.
> Aso the changes that were needed had nothing to do with tolerances, there were some basic design changes such as the size of the breach. It also doesn't explain the problems with the ammo.



You are right, they didn't work but the explanation, "official" or not has little to do with sloppy workers or "blue-eyed blondes" helping sabotage things. 

A big part of the reason _WAS_ money. The ammo makers get paid for for ammo that passes inspection which includes firing tests. If the ammo won't function in the "American" test gun with the long chamber they have made a lot of ammo that will be rejected and they won't be paid for. Too many rejected lots of ammo and the company might loose the contract. They might have shaded the tolerances to the long side or a larger shoulder so the ammo would function acceptably in the "american" gun which means it would give trouble in the British short chamber gun. There was also some dispute about greased ammunition or coating with hard wax. Both will improve the function of a "clean" gun but increase the stoppage rate in a dirty gun or dirty environment. Greased or wax coated ammo being basically dirt magnets. Wax being somewhat better than oil or grease.


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## zjtins (Mar 11, 2013)

I find much of the info to date misleading. Comparing energy of chemical (explosive) vs mechanical is pointless. The do not have the same affect on a target. 

A .50 solid bullet can destroy a water cooled engine in 1 shot. A 20mm thin shelled round may explode on the engine's surface and essentially do nothing. 

A .50 cal bullet can punch a .50 hole through Aluminum skin and do nothing, a 20mm thin walled shell can strip whole sheets of skin off a target aircraft when the aircraft is moving at high speed.

Many of the write ups to date are too simplistic.

There are several important categories that must be considered that a round needs to deal with, air vs water cooled engine, self sealing vs non sealed fuel tanks, small vs large aircraft (or lightweight vs robust). Also important are pilot or other armor, and round dispersion (based on distance to target and, gun positions and muzzle velocity/round drag). 

In the Pacific 6x.50 cal in the wings was perfectly acceptable to shoot at non sealed fuel tanks and unarmored aircraft. Very few bullets and the plane was in flames
In the Europe 6x.50 cal in the wings also worked enough. And the P-47 damage reports with its 8 fifties were never questioned.

But 4x20mm the FW-190 and other aircraft used were also very effective. May of the Russian aircraft used 1 or 2, 20-23 mm centerline (or near to) in their fighters and found them to work on German aircraft. 

Also many of the expert German pilots found the 1x 20mm center line to work well for them.

The .30 cal was universally scoffed at but in the beginning (BOB) 8 per aircraft was standard in England. They would use typically half there load to bring down 1 German but it worked. 

Before a serious comparison can be made the conditions must be understood. 
Shooting down a Zero vs B-17 are not the same in terms of gun needs. I have seen reports of many pilots taking down 3, 4, 5 even 7 Japanese aircraft in 1 battle. The best the Germans ever did was 2 B17's no matter what armament/airplane they used (in one battle). 

When asking the question we must make sure the comparison is valid when the results are in.


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## gjs238 (Mar 13, 2013)

zjtins said:


> The .30 cal was universally scoffed at but in the beginning (BOB) 8 per aircraft was standard in England. They would use typically half there load to bring down 1 German but it worked.



Not defending the .30 cal, but can't help but wonder, what % of load was typically used for .50 cal kills?


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## Njaco (Mar 13, 2013)

gjs238 said:


> Not defending the .30 cal, but can't help but wonder, what % of load was typically used for .50 cal kills?



I don't think he knows. That post is all he posts - check his other posts. They're all the same.


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## zjtins (Mar 15, 2013)

That is because the same argument is in many, many threads. 

For the .50 depends on target. 

And SBD with 2x.50 shot down 4 zeros in one fight.
A P-47 shot down 5 or 6 Germans in 1 fight.
A Red tail sunk a destroyer with 6 x.5. 
The all had ammo left over.

Bob Johnson in his P-47 had a FW-190 run dry over 300x 8mm hits and he still made it back. A FW-190 can carry 1800 rounds (possible, not know if this was actually on the plane the time the attack took place)
A ME-109 shot down a P-51 with 1x20mm shot. 

Of course for any plane it depends on surprise (less bullets), pilot experience (greater - less bullets), target ruggedness (fewer for a Zero than a B-17), speed, angle of attack, wind, gun location (wings, centerline etc)... 


This is my point the past discussion are only about the gun and not everything else, and not supported with data just gun round specs.


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## Matt308 (Mar 15, 2013)

zjtins said:


> That is because the same argument is in many, many threads.



Well since you do not read PMs from moderators, I'll post it here for all to see. If you keep posting the same stuff verbatim, you are gone. You can have a consistent position, but cutting and pasting paragraphs of the same text over and over is not participation, but considered spamming. We look forward to your next posts that contain some diversity on content.


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## tomo pauk (Mar 15, 2013)

The Red tail sinking of a destroyer being a myth?


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## zjtins (Mar 25, 2013)

No its a fact. Look it up, he got a medal for it, and gun camera film.

Also in the east many small boats were sunk from about every American fighter and several larger boats from solid nose B25's including destroyers.


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## DerAdlerIstGelandet (Mar 25, 2013)

zjtins said:


> No its a fact. Look it up, he got a medal for it, .



If it was sunk, then how were the Germans able scuttle it almost a year later?

The boat was not a Destroyer, but actually s Torpedo Boat. It was the T22, and was attacked by the "Red Tails" on 25 June 1944. It was put out of action but not sunk. The Germans ended scutteling it in Feb. 1945.

There are s lot of myths that are passed on as truth with the Red Tails. Do you also believe that they never lost a bomber?


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## tomo pauk (Mar 25, 2013)

zjtins said:


> No its a fact. Look it up, he got a medal for it, and gun camera film.
> 
> Also in the east many small boats were sunk from about every American fighter and several larger boats from solid nose B25's including destroyers.



I was hoping you would prove the claim. Alas, here are the Tuskegee airmen myths, the 'sunken destroyer' is one of them.

http://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&ved=0CDQQFjAA&url=http%3A%2F%2Fwww.tuskegee.edu%2Fsites%2Fwww%2FUploads%2Ffiles%2FAbout%2520US%2FAirmen%2FNine_Myths_About_the_Tuskegee_Airmen.pdf&ei=3pFQUbaQEKW74AS4kICIBg&usg=AFQjCNGo_3keLwlZ45zyxyBg734eQh66_Q&sig2=noH8ayRRe3HLCvoYy9pSJQ&bvm=bv.44158598,d.bGE

Sinking 'several small boats' was indeed what a battery of HMGs was capable for, that again does not prove that a destroyer was ever sunk by them. The solid-nose B-25s were sinking the bigger ships with bombs, not HMGs.

The destroyer that was heavily damaged by the Tuskegee airmen was the ww1 warship, with displacement of 615 tons. The ww2 USN and IJN destroyers were displacing easily over 2000 tons.


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## zjtins (Mar 25, 2013)

I guess we are are both incorrect. 


> ... on June 25, 1944 was the TA -22, the former Italian destroyer Giuseppi Missori.
> The date and the place match the group mission report. However, the TA - 22 had been converted by the Germans into a
> torpedo boat, and was no longer a destroyer. Al though it was so heavily damaged that it was put out of action permanently,
> it did not sink . It was decommissioned on November 8 , 1944, and scuttled at Trieste on February 5, 1945. It might as well have been sunk on June 25, 1944, because it never fought the Allies again...


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## DerAdlerIstGelandet (Mar 25, 2013)

Point being it is another myth that it was "sunk". Just like never losing a bomber they were escorting. Unfortunately if you speak out against these myths, you are racist.


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## bob44 (Mar 25, 2013)

> Point being it is another myth that it was "sunk". Just like never losing a bomber they were escorting. Unfortunately if you speak out against these myths, you are racist.



Iam not racist. But I did discuss the "never lost a bomber" thing with a black gentleman who is in the USAF, he did not care for the word "myth", but rather used the word "inaccurate". We'll just let it go at that.


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## zjtins (Mar 26, 2013)

They video shows explosions. I consider it fog of war. 

Best example is a book on C130 Spookies. They thought 20mm in Vietnam laid waste to everything. Finally did a test and found most of the trucks they shot up were drivable. The AF changed the rules to count them as destroyed only when the blew up or burned. The numbers went down but more importantly they would stick around shooting until they got a more decisive kill.


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## zjtins (Mar 26, 2013)

Never lost a bomber is not relevant in today's terms. The loss rates were way down when the Red Tails covered the bombers. In WWII that was huge. Men invent stories to help them deal with the horrible situations they faced. Today we look at it from a pristine view. To me no losses vs few losses mean nothing, in terms of the bomber crews was what counted. 

Its the same myth that a Tiger tank took five Shermans to kill it. Some took out many Shermans and were never put out of action. Others ran out of gas and were 'killed' several times over by Shermans making sure it was not a threat. FoW and perception, it happens


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