# Why was the US the only nation to rely on the 50



## MacArther (Dec 6, 2005)

I know that other nations, like Germany and Japan changed caliburs late in the war, but why was America the only one favoring the high calibur machine gun rounds from the get go? As for the rebuttle that Germany and Britain used 20mm, that is *not* a machine gun. That is a cannon.


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## the lancaster kicks ass (Dec 6, 2005)

the british loved the .303 baisically, we had so much ammo for them it was like we were shitting it out, when we realised we'd need something heavier we went straight to the 20mm.............


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## MacArther (Dec 6, 2005)

Yes, but why was the US the only one using the 12.7mm (/50 cal) early in the war?


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## DerAdlerIstGelandet (Dec 6, 2005)

The Germans were using 13mm and 15mm from the beginning.

*Fw 190A-8/F-8:*
Two 20mm Mg 151/20 wing mounted cannon.
Two *13mm Mg 131 *fuselage mounted machine guns.

*Bf-109F*
One *15mm MG 151 *mounted between cylinder heads and firing through the propeller hub.
Ammunition: 200 rounds
Two 7.9mm MG 17 mounted above engine.
Ammunition: 500 rounds per gun.


Also you do not count the 20mm because it is a Cannon, however that was the standard Germany heavy armament from the beginning of the war.


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## carpenoctem1689 (Dec 6, 2005)

The americans had some trouble with 20mm weapons, so most aircraft lacked them, i think the first to carry any were maybe the P-38. They liked the .50, and had weapons in the army and navy that also used the same calibre, maybe to ease production and logistics and distribution problems, by focusing on one calibre. Many early american fighters had .30 cal guns though too. The P-40 initially did, or the AVG had some that did i know that, the P-39 did, and many bombers were armed defensively with them.


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## donkeyking (Dec 6, 2005)

I think 12.7mm machine gun is powerful enough to fight against Axis's planes.

12.7mm machine gun has many advantages to compare 20mm canons.

A 12.7 mm gun shoots fast than a 20mm canon, and a round of 12.7mm is lighter than 20mm. So a plane can carry more 12.7mm rounds. 

And then, for a poor armour planes (fighter planes or light bombers), 12.7 mm machine guns have the same effect as 20mm canons.

It is lucky for us, Axis countries could not develop a mature heavy armour plane as B17, B24, B29 and Lancaster.

However when Russian has Tu4 (Russian version B29) after WWII, American find 12.7mm machine guns and even 20mm canons are not power enough against it. Aero-Rockets became standard equipments.


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## Jabberwocky (Dec 6, 2005)

The USAAF found itself in a postion where the .50 calibre was really the only feasabile weapon it could arm it planes with. There are a couple of reasons;

US attempts to mass produce a 20mm cannon were generally unsucessful. There was an attempt to alter the gun to be produced to US specifications which never really worked. Most of the 20mms were shipped to the UK. The British found them unsatisfactory compared to their own Hispano production. They had a much higher rate of jamming and breakdowns than UK produced cannon. See this article http://www.quarry.nildram.co.uk/US404.htm for a good history of US attempts to produce the Hispano.

Similarly, the attempt to produce an indigenous Very Heavy Machine Gun also failed. There was a program to re-engineer the Mg151/15 into a .60 calibre (15.3 mm), very high velocity machine gun. Like the 20mm program, it really didn't result in a workable design isn the wartime period.

The other reason that the USA stuck with the .50 is basic economics. The .50 was an aqequate, if not excellent, air to air weapon. It was already standard fit on most US fighters. Upon entering the war there were significant stocks of weapons and ammunition available for increased production. 

So, why change to a new weapon, when the .50 cal was 'good enough' for the job at hand? Switching to a new weapon would poentially disrupt production, require redesigns of weapons bays and render stockpile of weapons unnneeded.

More than anything the 'sunk' costs of the .50 kept it as the standard weapon for WW2 for the USA. My personal feeling was that the .50 was kept for reasons of structural inertia. There was 
a) singinficant infrastructure developed before the war to produce the weapon (production facilities, usage, logistics), 
b) existing designs incorporated the weapon as standard 
c) the future of other weapons programs were uncertain in their results
d) logistics concerns of new ammunition types


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## Glider (Dec 6, 2005)

A lot of Jaber posted makes sense but its worth remembering that the Italian Airforce and the JAAF also depended on the 12.7.


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## Jabberwocky (Dec 6, 2005)

You also can't forget that the VVS (Russian Airforce) used the UB and UBS 12.7mm weapons as standard from the beginning. They were fitted to the I-153, I-16 and LaGG-3 at the start of Operation Barbarossa. It was also fitted to the Yak family of fighters. The UB and UBS were the best heavy machine-guns of the war ( I tend to count the MG 151/15 as a cannon). They fired a longer, heavier shell than the Browning, with more than twice the HE capacity, at a faster rate of fire, with similar muzzle velocity, from a lighter gun. Pound for pound the UB was about 1/3rd more effective than the .50 calibre Browning.


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## book1182 (Dec 6, 2005)

I feel the .50 was kept as stated above. Good rate of fire, good hitting power and the main reason was because it was effective against both bombers and fighters.


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## DerAdlerIstGelandet (Dec 6, 2005)

I agree. It was effective and an all around good weapon, why replace it?


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## GregP (Dec 6, 2005)

Simple, we started replacing the 12.7 mm (50 cal) Browning when it was found that the speeds of aircraft were getting to the point where only a short burst could be expected to hit. Once taht happened, weight of fire per second was more important than rate of fire per second.

By the time we mounted 30 mm cannons, one hit in a vital area would disable a plane, if not shoot it down.

The A-10 shoots depleted Uranium rounds that have enough muzzle energy to penetrate a tank with one round.

Think of the Me 262. It was 100 mph faster than the P-51. In a dogfight, if there ever WAS one (which I doubt), the P-51 could not hit the Me 262 with enough rounds in a short burst to do significant damage before the plane was out of the line of sight. It took hits on the engines to slow the Messerschmitt down.
As long as you have only a small chance of a hit, a more energetic round is indictaed.


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## lesofprimus (Dec 6, 2005)

> Think of the Me 262. It was 100 mph faster than the P-51. In a dogfight, if there ever WAS one (which I doubt), the P-51 could not hit the Me 262 with enough rounds in a short burst to do significant damage before the plane was out of the line of sight. It took hits on the engines to slow the Messerschmitt down.


WTF are u talking about dude??? The -262 didnt fly around with his engines at full throttle...


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## carpenoctem1689 (Dec 6, 2005)

I think its more the only examply he could come up with that would relate to the topic at hand, from world war two anyway. I would have used the Corsair and the Mig-15 as my example, but thats me.
But when you look at whats said it does make sense, you could throw a bunch of 12.7mm rounds at a Mig-15, and the damn thing would just keep on flying (damn russians and there rugged construction) but the Mig, armed with a 37mm cannon and two 23mm cannon would rip a P-80 or F-86 to shreds with a small amount of hits. They were built to intercept bombers, and were therefore armed with good quality russian cannon for the job, but admittedly with much less ammunition than the six 12.7mm of the F-86.


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## DerAdlerIstGelandet (Dec 6, 2005)

GregP said:


> Simple, we started replacing the 12.7 mm (50 cal) Browning when it was found that the speeds of aircraft were getting to the point where only a short burst could be expected to hit. Once taht happened, weight of fire per second was more important than rate of fire per second.
> 
> By the time we mounted 30 mm cannons, one hit in a vital area would disable a plane, if not shoot it down.
> 
> ...



Um we are talking about WW2 here and at the end of the War the .50 Cal was still the standard armament on US aircraft. It was effective still at that time.

*P-38L:*
20mm Hispano M2(C) Cannon with 150 rounds
Four .50 Colt-Browning MG 53-2 m.g. with 500 rounds per gun.

*P-51D:*
2 × 0.50 inch Browning MG53-2 fixed forward-firing in the wing, 400 rounds each (inboard pair)
4 × 0.50 inch Browning MG53-2 fixed forward-firing in the wing, 270 rounds each (outboard pairs)

*P-51H:*
6 × 0.50 inch Browning MG53-2 fixed forward-firing in the wing

*P-47N:*
8 × 0.50 inch Browning MG53-2 fixed forward-firing in the wing leading edge, 425 rounds each (max, typical 267 each)

*P-47M:*
6 or 8 × 0.50 inch (12,7 mm) Browning machine guns

As for the A-10 and depleted Uranium Rounds that is completely different technology and is irrelevent to WW2 aviation.

As for the Me-262, single shots of just about anything in the engine would kill the aircraft not just slow it down. The engines were the Me-262's real weak point. The engines were not reliable and failed often eneogh on there own.


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## Glider (Dec 7, 2005)

A still believe that if the USA had been forced to take on a plane such as the B17 or B29 the 0.5 would have been found badly lacking. All forces that faced these planes went up to 30mm guns and the 0.5 would ave lacked the punch.
The 0.5 was only effective because of the planes it had to fact i.e. single engined planes, mainly pre war twins, and highly inflammable Jap bombers. Even B25's and B26's wold have proved a handful.


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## syscom3 (Dec 7, 2005)

The .50 had plenty of kinetic energy to deal with heavy bombers.


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## Glider (Dec 7, 2005)

Then why did all the airforces that faced them had to go up the 30mm cannons?


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## Gemhorse (Dec 7, 2005)

One point also, the British were indeed interested in arming-up with .50's, about the time after the Lancaster came on stream, but by then the US was into the War, and their demand delayed a serious introduction earlier...The British .303's had a high rate of fire, a ''good spray'', but they eventually had .50's in Spitfires [with cannon] and Lancasters got two of them in their rear-turrets later on too....The earlier variants of Mustangs that the RAF got were eventually fully up-graded from .30 cal to .50's too......


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## DerAdlerIstGelandet (Dec 7, 2005)

While I somewhat agree about .50 cal, the 20mm and 30mm were better suited for heavy bombers such as the B-17.


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## CurzonDax (Dec 7, 2005)

But I think the bottom line is this, logistics and supply. Its great weapon, but not the best, and it will do the job well, not great but well. Look at Pratt Whitney. The did build kickin engines but again supply and demand. Also the .50 has a higher cyclic reate than many cannons of its time and it has withstood the test of time, the fifties of today are not much more different than thier ones 60 years ago. Also to fire one is like to have the hand of the Goddess in your hands. Also I bet that B-17 armourors liked to carry a fifty around to install much better than a cannon!

:{)


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## syscom3 (Dec 7, 2005)

I dont think the Germans had armed their fighters with a full compliment of six heavy MG like the US did. remember, that when the war began for the US in 1941, there were two fighters that were designed from the outset to handle high flying "enemy" bombers. The P38 with its concentrated firepower which acted like a buzz saw, and the P47, which had eight .50's which would have ripped apart its opponant, just from the ammount of lead flying through the air.


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## Glider (Dec 7, 2005)

As a defensive weapon for bombers I have always believed that the .50 was more or less an ideal weapon. It had range, accuracy and you could put twins in a turret giving you a good rate of fire. 20mm in a turret would be too heavy.
However as you will have noted to take on a Heavy Bomber I believe that you needed something bigger.


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## carpenoctem1689 (Dec 7, 2005)

The 12.7mm was perfect for bomber defense, because like stated above, it was lighter then cannons, had a great fire rate, good range and decent enough power to deal with interceptors. The 12.7mm, unless concentrated, or used in high numbers (six to eight) wasnt the best anti-bomber weapon, because youd have to get in close enough to be in the enemies defensive range, and you couldnt bring him down too quickly. But cannon arent as effective against fighters because they have a slower rate of fire, and that decreases the chance of hitting a small, fast aircraft. So they tended to go overboard with 12.7mm (p-47 had eight, some say adequate, i say a little too much) or go with all cannon (Tempest, some spitfires and hurricanes, typhoon) or my favorite, mix up two cannon, two machine guns. The 12.7mm was perfect fopr defense, and adaptable to attack.


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## syscom3 (Dec 7, 2005)

The problem with mixed armorment is the different trajectories the shell would have. I think some P38 pilots disliked the 20mm because of that.

I always did think the B17/B24/B29 should have have a pair of 20mm or 30mm cannons.

Off topic, but the B52's had a .50's for the tail gunner, untill the advent of the vulcan cannon.


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## lesofprimus (Dec 7, 2005)

Yes syscom, Ive heard the same thing from some Vets, concerning the 20mm trajectory compared to the .50's...

Then again, Ive also heard that some loved the 20mm for the extra puch it carried.... You can never make everyone happy all the time....

(except the Sturmgruppen pilots)


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## CurzonDax (Dec 7, 2005)

There is also the cyclic rate. One of the reasons why the P-47 and the Lightning could plow the field was the higher cyclic rate of the .50 compared to the cannons of its contemporaries. Yes the rounds were smaller and the range was shorter in the .50 but more bullets were flying downrange than a cannon.

:{)


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## Jank (Dec 7, 2005)

The range of the .50BMG was not shoretr than any of the 20mm rounds used in the war. 

The .50 had a flater trajectory due mostly to its high sectional density, ballistic coefficient and velocity.


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## Jabberwocky (Dec 7, 2005)

Lunatic posted a very good giude to the ballistic properties of various aerial weapons of WW2. 

http://members.cox.net/rg_lunatic/gunpage/

and Rings PRO page also has an excellent technical comparison between the various fighter armaments, if his service privider ever fixes the bloody hosting problems it has been having!


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## Glider (Dec 8, 2005)

All guns are different and there was a significant difference between the best and worst of any calibre. However if we are comparing the USA M2 .50 against the standard British Hispano II the cyclic rate was similar.

M2 13.5 rds per second
20mm 10 rds per second

slower certainly but the 20mm was quick enough for the job.


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## syscom3 (Dec 8, 2005)

Doesnt the 50 cal have a longer sustained rate of fire?


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## Glider (Dec 8, 2005)

To be honest I don't know but the ideal burst for any fighter pilot was 2 seconds so I don't really know how important that was.

At the end the M2 was more accurate at long range as the gun ballistics were better but the 20mm carried 8-10 times the explosive so was far more effective when it hit. As the M2 wasn't 8-10 times more accurate the advantage was definately with the 20mm.


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## Jank (Dec 8, 2005)

The 20mm did not carry "8-10 times the explosive" compred to the .50 BMG because the .50 BMG bulets had no explosive. Ball, armor piercing and incindiary. Thats it.


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## Glider (Dec 8, 2005)

Let me rephrase that to Incendary material.


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## Jabberwocky (Dec 8, 2005)

A 20mm Hispano HEI (High Explosive Incidenary) round carries about 10 1/2 grams of explosive material.

A 12.7 M8 API (Armour Piercing Incidenary) carries about 0.85 grams of incidenary material.

So a Hispano HEI round carries about 12 time the amount of chemical material that a .50 cal round does.

Obviously, the 20mm HEI round is going to have significantly more blast/overpressure, fragmentation and ingintion effects than the smaller M2 round. 

Standard belting for the Hispano from 1942 was a 50/50 mix of AP ball and HEI. I'm not sure about the M2 belting, but I think that it was something like API-AP-API-AP-Tracer.


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## wmaxt (Dec 8, 2005)

The tracer round had a different trajectory than other .50 pounds.

As for loadout, often in the Pacific P-38 groups used no tracer rounds and their kill count went up. The count went up because they relied on the gun site rather than the tracer for more accurate aiming and the lack of a tracer (no warning for the target) allowed a second try if the first didn't connect.

wmaxt


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## DerAdlerIstGelandet (Dec 9, 2005)

CurzonDax said:


> Also the .50 has a higher cyclic reate than many cannons of its time and it has withstood the test of time, the fifties of today are not much more different than thier ones 60 years ago.
> :{)



The .50's of today are the same one from 60 years ago. They have just been overhauled. We have several .50's in my unit and they were manufactured in 1942.



syscom3 said:


> I dont think the Germans had armed their fighters with a full compliment of six heavy MG like the US did.



Depends on the fighter you are talking about:

*Dornier Do-335B-2*
Two 20mm MG 151/20 machine guns above the nose
Two 30mm Mk 103 cannon mounted in the wings.
One 30mm Mk 103 cannon firing through the propellor hub.

*Fw 190A-3*
Two 7.92mm MG 17 machine guns above engine.
Two 20mm Mg 151/20 cannon mounted in wing root.
Two 20mm MG/FF cannon in outer wings.

*He 219A-2/R1*
Two 20mm MG 151/20 Cannon in wing roots.
Two or Four 20mm MG 151/20 Cannon in belly tray.
Two 30mm Mk 108 cannon in Shräge Musik mount.

*He 219A-7/R1*
Two 30mm Mk 108 Cannon in wing roots.
Two 20mm MG 151/20 Cannon in belly tray.
Two 30mm Mk 103 Cannon in belly tray.
Two 30mm Mk 108 cannon in Shräge Musik mount.
Ammunition: 100 rounds per gun

*He 219A-7/R2*
Two 30mm Mk 108 Cannon in wing roots.
Two 20mm MG 151/20 Cannon in belly tray.
Two 30mm Mk 108 Cannon in belly tray.
Two 30mm Mk 108 cannon in Shräge Musik mount.
Ammunition: 100 rounds per gun

*Bf-110G*

Armament:
Nose: Fixed firing forward
Two 30mm Mk 108 Cannon with 135 rounds per gun
Two 20mm MG 151 Cannon with 300 rounds(port) and 350 rounds(starboard)
And
Two 20mm MG 151 Cannon in Shrage Musik Installation (Firing Obliquely forward)
Or
Two 7.92mm MG 81 in rear cockpit

Optional:
Waffenwanne 151Z ventral tray housing two forward firing 20mm MG 151 cannon


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## 102first_hussars (Dec 9, 2005)

MacArther said:


> I know that other nations, like Germany and Japan changed caliburs late in the war, but why was America the only one favoring the high calibur machine gun rounds from the get go? As for the rebuttle that Germany and Britain used 20mm, that is *not* a machine gun. That is a cannon.



Well Canada still uses the 50.cal as a platform machinegun and Ill tell you that weapon is a bastard to carry in the feild, shit that thing weighs close to 100lbs, personally I wouldnt have even gone with the lighter 30.cal.

But the Brits and Canadians used 50.cals in our bombers and spits, and in some cases we mounted them oon our shermans.


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## syscom3 (Dec 9, 2005)

The german fighters looked like they got plenty of cannon, but not 12.7mm MG


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## DerAdlerIstGelandet (Dec 9, 2005)

102first_hussars said:


> [
> Well Canada still uses the 50.cal as a platform machinegun and Ill tell you that weapon is a bastard to carry in the feild, sh*t that thing weighs close to 100lbs, personally I wouldnt have even gone with the lighter 30.cal.



It weighs more than that. In order for a unit to carry it on foot, you have to break it down into 3 parts. The Barrel, the Reciever Assy, and the Tripod Assy. It takes 3 people to carry the .50. That is why in the US, it is only a crew served weapon and is mounted on Tanks, Helicopters, and Vehicles now adays. 



syscom3 said:


> The german fighters looked like they got plenty of cannon, but not 12.7mm MG



For MG's they did not have 12.7mm anyhow. They used 7.7mm and 13mm mostly.


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## 102first_hussars (Dec 9, 2005)

It weighs more than that. In order for a unit to carry it on foot, you have to break it down into 3 parts. The Barrel, the Reciever Assy, and the Tripod Assy. It takes 3 people to carry the .50. That is why in the US, it is only a crew served weapon and is mounted on Tanks, Helicopters, and Vehicles now adays. 

We cant use it on vehicles and whatnot (we used too) since we are sooo commited to the U.N.  its actually illegal to use it on vehichles because that means we would usually be shooting at people, (they want us to use it against vehichles)

I can sorta see why because if you by any chance survive a shot by a 50.cal youre a vegitable for the rest of your life, were phasing the weapon out and chances are when the U.S comes out with a new HBHMG well get that one.


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## DerAdlerIstGelandet (Dec 9, 2005)

No we mount the .50 on the vehicles. We abide the Geneva Convention also, just like Canada. We are only supposed to use it against hard targets, not soft targets like soldiers. However if you read up on the Geneva Convention. Personell in the Vehicles are fair game, because you are not directly shooting at them.


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## Jabberwocky (Dec 9, 2005)

As the USA is not currently a signatory to the 1977 protocols of the Geneva convention, I am not sure if it abides by all the provisions of the convention. It does generally follow the accepted 'rules of war' but recently there have been several official complaints put foward by the International Red-Cross. As far as I am aware it is a signatory to Conditions I-IV of the 1949 Convention Conference, as well as the eariler 1906 and 1923 Conventions. However, as it is not a signatory to the International Criminal Court, I don't think that actions can be brought against it even if it does violate agreements it is signed to.

Certainly the US used .50 calibre weapons in anti-personnel roles in the Vietnam canflict. Whether this has changed more recently, I don't know.


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## DerAdlerIstGelandet (Dec 11, 2005)

What you have been hearing about recently is about the CIA not about the Military. As a member of the US Army I am trained on the Geneva Convention Laws and am ordered to abide by the laws of the Geneva Convention.


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## Jank (Dec 11, 2005)

Who says it's against the geneva convention to shoot people with the .50 BMG? 

Even in WWII, it wasn't comsidered an atrocious thing to strafe troops with the .50 BMG.


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## DerAdlerIstGelandet (Dec 11, 2005)

The .50 today is actaully only to be shot against vehicles not soft targets. It happens anyhow though, and I dont care, if you are in an armed conflict.


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## Glider (Dec 13, 2005)

I admit to never reaslising the the Geneva Convention went to such level of detail.
I suggest the desk bound jobs worth who thought that one up, should be put in a combat situation and then told that he cannot use the most effective weapon he has. Strongly suspect that a change of mind would follow.


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## evangilder (Dec 14, 2005)

I agree Glider. If you have bad guys coming at you, you want the most effective weapon to stop them. And when the fit hits the shan, you will take whatever you can get. 

"Gee my M-16 is out of ammo, but I can't use the .50 cal..."
Never happen.


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## Jank (Dec 14, 2005)

Would someone be kind enough to point me to teh specific paragraph or sentence that say you can't use a .50 BMG against people?

It is not prohibited by the Geneva Conventions.


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## Glider (Dec 14, 2005)

Chapter 16, section 3,, subsection 4, paragraph 6, of the third volume, second redraft, of the 4th revision, page 265.


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## Jank (Dec 14, 2005)

Seriously though, the Genev Conventions does not prohbit the use of the .50 BMG on people. Just because the military has a policy doesn't mean that policy is rooted in the Geneva convention. American snipers have been using the .50 against persons for years now. Look at this link . (Do not open it if you are not prepared for a very graphic image.)

http://poetry.rotten.com/failed-mission/failed-mission.jpg

Use of heavy caliber machine guns aganst troops, whether from a sniper rifle, atop a tank or on fighter aitrcraft, has never shocked the conscience of the combatants in war.


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## Lunatic (Dec 15, 2005)

Jabberwocky said:


> A 20mm Hispano HEI (High Explosive Incidenary) round carries about 10 1/2 grams of explosive material.
> 
> A 12.7 M8 API (Armour Piercing Incidenary) carries about 0.85 grams of incidenary material.
> 
> ...



The modern and late WWII M8 rounds carry about 0.9 grams of IM11 incendiary metal composition (50% barium nitrate, 50% Aluminum/Magnesium), and a moly-steel penetrator. However, the M8 introduced in late Summer 1943 had a tungston carbide penetrator (much heavier than moly-steel) which was smaller and allowed a 1.5 gram IM11 payload. These were used through 1944 when, in order to conserve tungston, the switch to moly-steel was made. At that point the war was already won and no enemy airforce was going to contest the skies. Some tungston core M8's were still being used through the end of WWII and beyond.

Typical loadings for the M2 using M8 ammo were 4 API: 1 Tracer-API. When the computing gunsight came into use in mid 1944, the tracers were usually dispensed with and pure M8 ammo was used. The difference in trajectory for the tracer vs. non tracer .50 ammo of approximately the same weight is mimimal since the round has an extremely flat trajectory out to 400+ meters. The reason P-38 (and other plane type) kills went up when the tracers were eliminated was because they had recieved the K-14 (or MK.18 for USN) computing gunsights which made it much easier to score at longer ranges, especially for high angle deflection shooting.

=S=

Lunatic


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## Lunatic (Dec 15, 2005)

The reason for the US commitment to the .50 has to do with forsight vs. response.

Well before WWII, in fact in the late 1920's I believe, the USA realized that as aircraft were becomming bigger and being made of metal vs. wood, the .30 caliber guns were insufficient to the task. So during the early 1930's they developed the .50 M2 Aircraft gun, which they considered heavy enough to do the job. The .50's were about as big as you'd want to mount on the aircraft of the early 30's.

Other nations stuck with the rifle caliber guns until experiance showed them these were too small for the job. The German's and Soviet's discovered this in the Spanish Civil war. As a result they developed 20mm cannon for their aircraft. Because the aircraft were bigger, a bigger gun was reasonable. The Soviets developed both the 12.7mm UB Bresin guns as well as the ShVAK 20mm cannon. The Germans developed the MG-FF based on the Oerlikon cannnons of, I believe, the Swiss. Later in the war, when the German's relized just how useless the 7.9mm was, they updated this to a 13mm, but the MG131 had to be designed to easly replace the MG17, so it had to have low recoil and fit on a single mounting point - so it was a weak gun and not really comparable to the other ~13mm HMG's.

The British did not realize their .303's were too small until the start of the war. At that point, they considered all their options, and the 20mm Hispano-Suza cannon was the best candiate already in production (as an AA gun). The British had no suitable .50 class gun in production so this really was not an option for them anyway.

The USA already had the .50 fully worked out and ready well before the start of WWII. Advances in production methods allowed the use of IM11 incendiary metal composition (which only the British were able to duplicate, but on a much smaller scale and with US technical assistance, in the form of their "DeWilde" .303 ammo). Other nations utilized inferior incendiary materials such as white phosorous or "elecktron", where the oxidizer (barium nitrate) was ground up and mixed with the incendiary metal in a wax based paste - almost fully defeating the self fusing nature of the IM11 composition used in US (and Brit) rounds (IM11 ignites from the crush of the hit and thus needs no fuse). The US did try to develop the 20mm, but it was never enough of a priority to get the funding needed to develop a really good one until the end of the war. Supply issues were also a factor - we had the logistics of delivering large quantities of a single ammo type down, where throwing in additional ammo types complicated things. Other nations often had problems with having pleanty of ammo in the field that did not fit the available guns. The German's often had problems with having pleanty of percussion primer 20mm when they needed electric primer ammo or visa versa.

As for .50's being able to take down a B-17, I personally think that a P-47 would make short work of a Fort. Eight .50's is a lot of firepower. I've seen a school bus cut in half in a few seconds by a single .50, and those old Bluebird busses (phased out for saftey issues so lots have been used for target practice) were made of steel not aluminum! A B-17 wing would last a second, two at most, under 8 x .50's fire.

Also, everyone keeps listing the RoF of the .50 as 750 rpms, yet points to RoF's for the Hispano II as 600 rpms, the MG151/20 as 750 rpms, etc... The maximum RoF of the Hispano II was 600 rpms, typical installed RoF's were lower. The same is true for the MG151/20 - typical installed RoF was about 710 rpms non-syncronized. The sync'd guns in the wing roots of the FW-190 were only about 490 rpm.

For the .50 aircraft gun, the factory RoF was 750-850 rpms for a brand new gun. As the gun wore in, the RoF went up (rather quickly at first - by the time the gun was sighted in and fully Q/C'd in the field, it'd gone up 30-50 rpm). So typical stock RoF was somewhere between 800 and 900 rpms. Also field armor's were known to install a nickle in place of a fiberous disk used as a backplate (to stop the reward motion of the reciever) which would boost the RoF by about another 100-150 rpms - this was very commonly done on P-51's fitted with 4 guns, less common for 6 gun setups (since it did tend to wear out the gun more quickly and sometimes crack the reciever though even cracked the gun usually operated okay).

So if we are going to use the max rates of fire for the 20mm cannon, shouldn't we also use the max Rof's for the .50's? In that case, 850 rpm seems a conservative number, and 900-1000 rpm would be within reason.

Finally, reliablity is also an issue. The Hispano II was probably the most reliable WWII 20mm cannon, and by 1945 they'd gotten the jam rate down to 1:1500 rounds fired. The .50 M2 jam rate was 1:4000 rounds fired at the start of the war, and improved from there to near total reliability (not counting bad belt layout issues in P-51B's which were solved via motorizing the feed). Also considereis that with 20mm wing mounted guns (outside the prop arc) if one gun goes out, it's mate is useless - on the Spitfire this meant the 20mm's were out of service - which is why they carried 2 x .50s. The recoil is too strong to trim out. With .50's, the recoil can be trimmed out so the mated gun can still be fired. Even on the AD Skyraider (a huge plane), if one 20mm jammed the mate on the opposite wing was useless. This forced them to goto 4 x 20mm on the AD-4 (as opposed to only 2 on the AD-2), not because they needed more firepower, but because far too often (about one in 3 sorties) the plane was toothless over the battle field due to a gun jam.

Most WWII 20mm armed fighters had only 2 x 20mm cannon. Four were too heavy for the Spit (the IXc is listed with 4 but almost always flew with only two installed), and the FW190 with 4 x 20mm was greatly depreciated as a fighter - this was a bomber destroyer configuration. The Typhoon was not much of a "fighter". The Tempest was the first competitive "fighter" by the Britsh to mount 4 x 20mm, and the Corsair was the first US fighter to do so. So really, we are generally comparing 6 x .50's to 2 x 20mm - and in this matchup I think the .50 armorment is clearly superior (for fighter vs. fighter combat, or for killing medium/light bombers).

Compare the Spit IX vs. the P-51B for fighter vs. figther combat. Which would you rather have? 2 x 20mm with 150 rpg firing at 600 rpm or 4 x .50's with 400 rpg firing at 950 rpm?

=S=

Lunatic


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## Jabberwocky (Dec 15, 2005)

""
Also, everyone keeps listing the RoF of the .50 as 750 rpms, yet points to RoF's for the Hispano II as 600 rpms, the MG151/20 as 750 rpms, etc... The maximum RoF of the Hispano II was 600 rpms, typical installed RoF's were lower. The same is true for the MG151/20 - typical installed RoF was about 710 rpms non-syncronized. The sync'd guns in the wing roots of the FW-190 were only about 490 rpm. """

The max RoF for the Hispano was actually considerably higher than the 600 rpm commonly listed. I have seen figures that suggest the RoF was much closer to 700 rpm. 

The Hs 404, the original French version of the cannon, was rated at 750-800 rpm. When the British adopted it they reduced the rate of fire in the Mk I to avoid case crushing causing jams. The 1940 RAF armourers handbook lists the RoF for the Mk I Hispano at 650 rpm. The 1944 RAAF report on the Beaufighter Mk 21 lists the RoF for the Hispano as 700 rpm. There are also reports of RAAF armourers adjusting the gun to give rates of fire as high as 1000 rpm. Not standard service figures of course, but enough to suggest that the 600 rpm figure for the Hispano is actually a little low. 

600 rpm is generally reported as the minimum figure for the Hispano, just like 750 rpm is generally reported as the minimum figure for the M2.

The LuftWaffe used electrical priming instead of pneumatic synchronisation for is cannon firing through a propellor arc. Generally speaking electric synchronisation was much more effective than pneumatic synch. The common listed figures (Tony Williams, Emmanual Gustin) are that the Mg 151/20 only lost 10% off its RoF when it wsas synchronised.


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## Glider (Dec 15, 2005)

A good posting but there are some points which I would comment on.

he British knew before the war that the 303 wasn't powerful enough and undertook some tests for an alternative. The .50 M2 wasn't chosen as it wasn't deemed to be a big enough improvement and the choice was made for the 20mm Hispano. We also knew that it would take time to get it right and a battery of 8 x 303 was sufficient. As we all know experience showed that this was at best a bare minimum but that is with the benefit of hindsight. 
At the time the 109 recognised as the major danger was only armed with 3 or 4 LMG's so 8xLMG was a powerful punch for the time particually against planes without armour or self sealing fuel tanks. The P36 of the time had I think 4 xLMG and other USA fighters had similar guns. The italians were arming their fighters of the time with 2 x HMG and the Japenese had 2 x LMG. SO don't be fooled into thinking that we were unconcerned about the firepower needed.

The DeWilde ammunition used by the RAF and 'borrowed' by the USA was a totally British development. The original DeWilde ammunition was developed in Europe and was the most effective ammo of its time BUT it was impossible to mass produce. We developed our own ammo based on a different principle and put that into mass production however we called it DeWilde as a rather poor attempt at security. It sounds odd I know but it is the real story.
One reason for the USA not developing a reliable 20mm had nothing to do with funding. It was the USA wouldn't put into production the modifications that we had used in the manufacture of our 20mm. If they had it would have worked. Both the USA and the UK started with the same basic gun the French 404 so there is no reason why the changes wouldn't have worked.
Re the ROF I don't see the logic as to why a .50 would speed up after some use whereas every other gun slows down. As automatic weapons are used they settle down and work more efficiently, its the same for every kind of machine. Its why you should run a new car in exactly the same principle. For that reason its why I would stick with the 600rps for the 20 and the 750 rps for the .50 its recognised as the standard figures. All mass produced guns varied in their performance.

As for field modifications I wouldn't count them unless all guns had the same changes as standard. I have heard of 20mm increasing their ROF by changes to the gun, but it was powerful enough without them. However most battlefield changes tend to damage reliability. These are precision pieces of equipment and sticking pieces of metal into the workings is unlikely to improve it overall. 

As for the P47 against the B17 again I don't see the logic. The FW190 had far more firepower than the P47. Why would the P47 find it easier than the Fw to shoot down a B17? 
The example of a bus being destroyed by a .50 is interesting but no more. I have seen a photo of a large tree cut in half by a Maxim in 1895 what does that prove? A 20mm fired at the bus would have blown it to Kingdom come, not just cut in half.

Reliability is something you mention. I have ready loads of articles on air combat and apart from the early days I have not heard anything about the 20mm being unreliable. I do know that the USA held test in which they fired 5000 rounds using a 20 from each manufaturer in the USA plus a British 20mm.
The British 20 firing British ammo fired all 5000 without a failure. The worst American gun had 97 jams in 3,600 rounds after which they gave up with that one. The others did do better, but none made it to the 5000 limit without some jams.

Compare Spit 9 with P51B
2 x 20mm plus 2 x .50 against 4 x .50 No contest.

Remember the USAF considered 1 x 20 to equal 2.5 x 0.50. So using USA figs its comparing 7 x .50 against 4 x .50


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## Glider (Dec 15, 2005)

Sorry everyone but I have found my info and there were some errors in my last post.

The 5,000 round test results were
British Mk II 19 Stoppages in 5012 rounds
American Gun 1 67 Stoppages in 4019 rounds
American Gun 2 97 Stoppages in 3,705 rounds
American Gun 3 94 Stoppages in 2,610 rounds

Pretty unimpressive I think you will agree. The British believed that the reliability was affected by the ammunition. British forces were specifically forbidden to Grease the ammo as it affected reliability.
US Forces were specifically told to Grease the ammo. The tests were done in the USA and the Ammo was greased. Without it we believed that the UK gun would have done better.

Re the comment about increasing the rate of fire of the 20mm. Molins produced a tweeked version that had a rate of fire of 1,000 rounds per minute but it was decided that the standard was good enough and it was better to wait for the MkV.


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## Lunatic (Dec 16, 2005)

Jabberwocky said:


> The max RoF for the Hispano was actually considerably higher than the 600 rpm commonly listed. I have seen figures that suggest the RoF was much closer to 700 rpm.
> 
> The Hs 404, the original French version of the cannon, was rated at 750-800 rpm. When the British adopted it they reduced the rate of fire in the Mk I to avoid case crushing causing jams. The 1940 RAF armourers handbook lists the RoF for the Mk I Hispano at 650 rpm. The 1944 RAAF report on the Beaufighter Mk 21 lists the RoF for the Hispano as 700 rpm. There are also reports of RAAF armourers adjusting the gun to give rates of fire as high as 1000 rpm. Not standard service figures of course, but enough to suggest that the 600 rpm figure for the Hispano is actually a little low.
> 
> 600 rpm is generally reported as the minimum figure for the Hispano, just like 750 rpm is generally reported as the minimum figure for the M2.



Aircraft evaluations I've seen indicate actual RoF's for the Hs.II of about 530 rpm, not 600 and certianly not 700 rpm. Whatever the guns were theretically capable of is not at issue. What is relevant is what RoF's they actually used.



Jabberwocky said:


> The LuftWaffe used electrical priming instead of pneumatic synchronisation for is cannon firing through a propellor arc. Generally speaking electric synchronisation was much more effective than pneumatic synch. The common listed figures (Tony Williams, Emmanual Gustin) are that the Mg 151/20 only lost 10% off its RoF when it wsas synchronised.



Yes, and they give no actual test reference for that figure. Instead, it relies on German design info. Manufacturers and Engineers often make overly optomistic claims. On the otherhand the Soviets tested many captured FW190's and consistantly reported the actual RoF at operating engine RPM of about 490-500 rpm for the wing-root cannons.

=S=

Lunatic


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## Lunatic (Dec 16, 2005)

Glider said:


> A good posting but there are some points which I would comment on.
> 
> he British knew before the war that the 303 wasn't powerful enough and undertook some tests for an alternative.



Check your sources. Britian didn't get serious about replacing the .303 until 1940. Experiance showed them 8 x .303's were not sufficient.



Glider said:


> The .50 M2 wasn't chosen as it wasn't deemed to be a big enough improvement and the choice was made for the 20mm Hispano. We also knew that it would take time to get it right and a battery of 8 x 303 was sufficient. As we all know experience showed that this was at best a bare minimum but that is with the benefit of hindsight.



The British had no suitable .50 class gun in production. They did have several 20mm's in production of which several were considered and the Hispano was finally chosen. I am quite certain that had the British had a .50 class gun ready to field and facilities for ammo production in 1940 they'd have used it. Since they didn't, they didn't.



Glider said:


> At the time the 109 recognised as the major danger was only armed with 3 or 4 LMG's so 8xLMG was a powerful punch for the time particually against planes without armour or self sealing fuel tanks. The P36 of the time had I think 4 xLMG and other USA fighters had similar guns. The italians were arming their fighters of the time with 2 x HMG and the Japenese had 2 x LMG. SO don't be fooled into thinking that we were unconcerned about the firepower needed.



All US fighters ordered for the USAAF and USN from 1937 on mounted .50 class guns.



Glider said:


> The DeWilde ammunition used by the RAF and 'borrowed' by the USA was a totally British development. The original DeWilde ammunition was developed in Europe and was the most effective ammo of its time BUT it was impossible to mass produce. We developed our own ammo based on a different principle and put that into mass production however we called it DeWilde as a rather poor attempt at security. It sounds odd I know but it is the real story.



The assistance was in how to mass produce it.



Glider said:


> One reason for the USA not developing a reliable 20mm had nothing to do with funding. It was the USA wouldn't put into production the modifications that we had used in the manufacture of our 20mm. If they had it would have worked. Both the USA and the UK started with the same basic gun the French 404 so there is no reason why the changes wouldn't have worked.



The US Hispano was based upon British specs, not French specs. However, the drawings had to be converted to US standards. Unfortunately, some idiot decided that, being a "cannon", the tolerances should be artillary grade, not machine-gun grade, and so the cannons were not very well built. Also the original British specs called for a chamber that was too long - the firing pin would fail to strike the primer hard enough to fire it. These problems was eventually resolved but led to long delays because, amoung other things, the 20mm was not a high priority and did not recieve the kind of funding other weapons systems recieved, nor the best engineers.



Glider said:


> Re the ROF I don't see the logic as to why a .50 would speed up after some use whereas every other gun slows down. As automatic weapons are used they settle down and work more efficiently, its the same for every kind of machine. Its why you should run a new car in exactly the same principle. For that reason its why I would stick with the 600rps for the 20 and the 750 rps for the .50 its recognised as the standard figures. All mass produced guns varied in their performance.



Blow back designs tend to increase in RoF when the springs weaken with use. Gas operated guns tend to decreace in RoF as the works get gummed up and the seals become less and less effective.

The only plane for which 750 rpm is quoted is the P-47, at 100 rps. The P-51D, F4U, Hellcat are all quoted at 80 rps from the factory.

80 rps / 6 = 13.333 ; 13.333 x 60 = 800

So 800 rpms is the reasonable figure to use if factory RoF's are to be used. However, in reality the gun fired faster by the time it reached combat.



Glider said:


> As for field modifications I wouldn't count them unless all guns had the same changes as standard. I have heard of 20mm increasing their ROF by changes to the gun, but it was powerful enough without them. However most battlefield changes tend to damage reliability. These are precision pieces of equipment and sticking pieces of metal into the workings is unlikely to improve it overall.



The "nickel trick" was the norm for P-51B's in both the 8th and 9th airforce. Armorers and pilots were known to write home asking for nickels for this purpose.



Glider said:


> As for the P47 against the B17 again I don't see the logic. The FW190 had far more firepower than the P47. Why would the P47 find it easier than the Fw to shoot down a B17?



Where did I say "easier"?

But, the P-47 does have several advantages. The .50's can be triggered longer than the MG151/20's, giving more chance to slice at the wings. The .50's also have substantially longer effective range. For this kind of target, the .50's would be effective out to over 500 meters, where the MG151/20's were effective to only a little over half that range. Finally, the P-47 has a volume of fire advantage - 100 rps vs. 41 rps.



Glider said:


> The example of a bus being destroyed by a .50 is interesting but no more. I have seen a photo of a large tree cut in half by a Maxim in 1895 what does that prove? A 20mm fired at the bus would have blown it to Kingdom come, not just cut in half.



But cutting it in half is all that is needed to down a B-17. Blowing it up doesn't make it any deader.

Also, fusing issues were a real problem for the WWII 20mm. Too often the 20mm would burst on the skin and fail to do any structural damage.



Glider said:


> Reliability is something you mention. I have ready loads of articles on air combat and apart from the early days I have not heard anything about the 20mm being unreliable. I do know that the USA held test in which they fired 5000 rounds using a 20 from each manufaturer in the USA plus a British 20mm.
> The British 20 firing British ammo fired all 5000 without a failure. The worst American gun had 97 jams in 3,600 rounds after which they gave up with that one. The others did do better, but none made it to the 5000 limit without some jams.



The official jam rate for the British Hispano II was 1:1500 rounds fired during the last 12 months of WWII. For the .50 BMG, it was 1:4000 rounds fired measured in 1942 when the USA entered the war. Steralite lined barrels were introduced in 1943-44, decreasing jam rates.

As I recall, in that particular test the British Hispano suffered about 20 jams in 5000 rounds fired - less than 25% that of US Hispano's tested. Still, 20:5000 is... *1 in 250 !*

There are many accounts of Hurc IIc's and Spitfires where all the cannon jammed in a single sortie.



Glider said:


> Compare Spit 9 with P51B
> 2 x 20mm plus 2 x .50 against 4 x .50 No contest.
> 
> Remember the USAF considered 1 x 20 to equal 2.5 x 0.50. So using USA figs its comparing 7 x .50 against 4 x .50



The Spit IXc typically flew with 2 x Hispano II's and no mg's. It was a hypothetical comparison anyway.

Besides, the .50's were not generally fired with the Hisapno's - it was one or the other since the trajectories were significantly different.

=S=

Lunatic


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## Jabberwocky (Dec 16, 2005)

Lunatic said:


> Aircraft evaluations I've seen indicate actual RoF's for the Hs.II of about 530 rpm, not 600 and certianly not 700 rpm. Whatever the guns were theretically capable of is not at issue. What is relevant is what RoF's they actually used.



Care to point out where these figures are from? The 600 rpm figure is given as the generally accepted figure for the Mk II Hispano. The RAF armourers booklet gives the official RoF for the Hispano MK II and the US AN M.2 as 650 rpm. That seems to me that the accepted figure for RoF should be between 600-650 rpm.



> The British had no suitable .50 class gun in production. They did have several 20mm's in production of which several were considered and the Hispano was finally chosen. I am quite certain that had the British had a .50 class gun ready to field and facilities for ammo production in 1940 they'd have used it. Since they didn't, they didn't.



If the British had wanted a .50 calibre aircraft armament, they could or turned to the locally made 12.7x81 Vickers. Instead, British testing by both the RAF and FAA with .50 calibre armaments (with both the Vickers and Browning) during the 1930s brought them to the conclusion that the .50 was neither fish nor foul. That is, it didn't have the high RoF and low weight of LMGs (7.5-7.9mm calibres) or the destructive HE punch of cannon found in the 20mm range. British testing in 1940 concluded that 20mm was the minimum calibre necessary for aerial warfare.



> The Spit IXc typically flew with 2 x Hispano II's and no mg's. It was a hypothetical comparison anyway.
> 
> Besides, the .50's were not generally fired with the Hisapno's - it was one or the other since the trajectories were significantly different



The Spitfire Mk Vc/IXc typically flew with 2 20 mm Hispanos and 4 .303 Brownings, not with just 2 Hispanos. The 4 Hispano and 2 Hispano armaments were the exception, rather than the norm. Generally the 2 Hispano armament was used only on the Spitfire Vc in the MTO. 

Despite the fact that the .303 and the 20mm have ballistic profiles even more disparate than the .50 and the 20mm, it was common practice to fire both together. Fighter pilots aren't well known for holding 1/3 of their weight of fire when presented with a target. At effective firing ranges (100-350m) the difference in trajectory is not that pronounced. 

The .50 was chosen as the armament for the E type Spitfire wing for several reasons. Firstly it had greater hitting power, range and armour penetration than the .303. Secondly, its ballistic profile more closely matched that of the 20mm. At usuable combat ranges (100-400 m) there is little very difference in the velocity or trajectory of either round. The Browning round had a slightly flatter profile, and held muzzle veolcity about 20% better as a result of a superior ballistic shape.


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## MacArther (Dec 16, 2005)

Wow, good discussion so far. How about the Japanese 13mm? I think it was only on one torpedo plane that had to be used from land bases because there were no carriers left by the time it entered service. On a side note, I would *hate* to be a Japanese armorer, imagine trying to get all the different amunition types, and making sure they were rimmed or unrimmed!


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## DerAdlerIstGelandet (Dec 16, 2005)

Jank said:


> Seriously though, the Genev Conventions does not prohbit the use of the .50 BMG on people. Just because the military has a policy doesn't mean that policy is rooted in the Geneva convention. American snipers have been using the .50 against persons for years now. Look at this link . (Do not open it if you are not prepared for a very graphic image.)
> 
> http://poetry.rotten.com/failed-mission/failed-mission.jpg
> 
> Use of heavy caliber machine guns aganst troops, whether from a sniper rifle, atop a tank or on fighter aitrcraft, has never shocked the conscience of the combatants in war.



You are more than likely correct. I can not quote a paragraph or page or anything. It is more than likely not an actual law. It is however during our Geneva Convention training pretty much stated in our policy on the .50 Cal. Now as you said Snipers do use the .50 Cal and yes in an actual combat situation I would have no problem using a .50 Cal on people.


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## Magister (Dec 16, 2005)

Thanks to that .50, it looks like that insurgent finally got his one way ticket to see Allah.


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## MacArther (Dec 16, 2005)

yes, he probably though, "I will do this for mySPLAT"


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## DerAdlerIstGelandet (Dec 16, 2005)

We need to see more like that.


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## Glider (Dec 16, 2005)

Sources checked. 
Initial tests were undertaken in the 1920's as it was recognised that 2 x LMG wouldn't be sufficient for long. Guns used were the Browning and Vickers 0.50 calibre and the Oerlikon 20mm Type S but no decision was made.
In the mid 30's aircraft had made significant improvements and it was recognised that the 303 was to small. In 1936 the French demonstrated the HS404 in Paris tests were undertaken and this was chosen for the RAF. An RAF ACAS report of 1938 stated that every effort should be made to ensure rapid production. In the meantime the decision was taken to increase the firepower of the latest planes (read Hurricane and Spitfire) to 8 x LMG. Its worth mentioning here that the Spitfire was originally designed for 4 x LMG and amended to 8 X LMG. Its one of the differences between a Spit 1 and a Spit 1a.

As outlined above the British did have 0.50 MG's in production, the Vickers which was developed into a quad mount AA gun for the Navy. We didn't have a 20mm in production. The Masden was the other 20mm that was compared to the HS404 in the 1936 tests.

Re the guns on USA Aircraft I think you will find that the first P40's only had LMG's, the P36 had LMG's and the P43 Lancer had 2xHMG and 2 x LMG. So even in the USA there was a certain amount of uncertainty.

We didn't need the help of the USA in mass producing the DeWilde ammunition technically. We had a shortage of production capacity across the board and this may have been the cause of some confusion.

The USA 20mm was definately based on the original French weapon. We were almost begging the USA to use our specs as we wanted to use these guns in our aircraft. In the end the USA provided thousands of 20mm to the UK under lend lease and we didn't mount a single one on an RAF aircraft. 
The major and most significant difference was the size of the chamber. I am afraid that you have it the wrong way around it was the UK chamber that was 1/16th of an inch shorter and its the one things the USA refused to change. As a result the largest cause of jams, soft striking continued in the US weapon and was rare in the UK weapon. The British observers noted and commented on the quality of finish of the USA weapons as being much higher than that of the UK gun. 

P51B guns were noted for their unreliability. The feed was awkward, the gun was mounted on an angle and it often jammed. I don't know if adding a nickle would have helped reliability, rof maybe but reliability I doubt. Do you know if they used the nickle on the P51D, Hellcat, P47 or anything else that used the .50 or was it just for the P51B?

I believe that your view of the .50 against a heavy bomber are flawed. Everyone who took on these aircraft upgunned preferably to 30mm. To believe that the 12.7 would do as well or even close to as well is in my view, very, very, optimistic. Me I would go with 4 x 20.

The fusing problems of the 20mm was a real problem early in their deployment. For that reason a number of RAF squadrons originally used all AP as it would do a lot of damage to whatever it hit but this was solved by 1942 when our fused would go off a fraction of a second after hitting the plane doing the most damage.

As for your comment on reliability my second post which presumably crossed covered that point but the results for the British gun would have been a lot better if the ammo hadn't been greased. If our's were bad the USA ones were awfull.

Spit 9's always had either 2 x 20 plus 4 x LMG or 2 x 20 plus 2 x HMG not just 2 x 20. As for firing the sign of an experienced pilot was using one gun to find the range and then letting fly but this was very rare. Nearly all pilots in all airforces would let fly with everything they had if an enemy was in front of them as tragically it was often the only chance they had.

The only UK fighter I have found that flew with only 2 x 20 were Hurricane IIc's, which sometimes had two of the guns taken out to improve performance over Malta.

Re Rate of Fire. The quoted one is normally 600rpm for the 20mm. The RAF Manual said 650, the test of a Beaufighter was 700 and the test of another plane was 530. None of these firures suprise me as mass production could make them vary by 10-15% of base figure. If you average them you get 620 which is so close to the 600 its not worth arguing about. If you cannot hit the plane with 600 rpm I doubt if you could hit it with 620. 
Personally I would like 2 of those Molins guns please. Then I would happily leave my 4 x LMG or 2 x HMG behind and carry extra ammo.


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## CharlesBronson (Dec 16, 2005)

MacArther said:


> Wow, good discussion so far. How about the Japanese 13mm? I think it was only on one torpedo plane that had to be used from land bases because there were no carriers left by the time it entered service. On a side note, I would *hate* to be a Japanese armorer, imagine trying to get all the different amunition types, and making sure they were rimmed or unrimmed!



The navy used two types of 13 mm Mg, one was the 13,2 Japanese Navy Type 3 13,2mm (13,2x99) rimless derivated from a French Hochtkiss cartrigde but in a Browning M2 gun, that was used in the Mitsubishi A6M5.







The other 13mm was the Type 2, a copy of the german Mg-131, it was emplaced as defensive armament in the late torpedo -bombers.


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## Lunatic (Dec 17, 2005)

Glider said:


> Sources checked.
> Initial tests were undertaken in the 1920's as it was recognised that 2 x LMG wouldn't be sufficient for long. Guns used were the Browning and Vickers 0.50 calibre and the Oerlikon 20mm Type S but no decision was made.
> In the mid 30's aircraft had made significant improvements and it was recognised that the 303 was to small. In 1936 the French demonstrated the HS404 in Paris tests were undertaken and this was chosen for the RAF. An RAF ACAS report of 1938 stated that every effort should be made to ensure rapid production. In the meantime the decision was taken to increase the firepower of the latest planes (read Hurricane and Spitfire) to 8 x LMG. Its worth mentioning here that the Spitfire was originally designed for 4 x LMG and amended to 8 X LMG. Its one of the differences between a Spit 1 and a Spit 1a.
> 
> As outlined above the British did have 0.50 MG's in production, the Vickers which was developed into a quad mount AA gun for the Navy. We didn't have a 20mm in production. The Masden was the other 20mm that was compared to the HS404 in the 1936 tests.



The Vickers was not suitable for a variety of reasons. Amount them I believe were the way the ammo feed worked, and the max RoF was too slow. It would have required a complete re-design. Ammo production was quite limited too.



Glider said:


> Re the guns on USA Aircraft I think you will find that the first P40's only had LMG's, the P36 had LMG's and the P43 Lancer had 2xHMG and 2 x LMG. So even in the USA there was a certain amount of uncertainty.
> 
> While the British were looking at the Hispano in the years immediately prior to the war, they did not get serious about it until the war had already started. My point is the USA had by this time already made a commitment to the .50, I believe in 1932 or so.
> 
> ...



No I had it right. The original spec called for a longer chamber, and the USA built their guns this way and it took a long time for them to adjust it as the British suggested AFTER THEY PROVIDED DRAWINGS SHOWING THE LONGER CHAMBER DESIGN. The US Hispano was based upon British drawings which had to be redrawn to US production specs.



Glider said:


> P51B guns were noted for their unreliability. The feed was awkward, the gun was mounted on an angle and it often jammed. I don't know if adding a nickle would have helped reliability, rof maybe but reliability I doubt. Do you know if they used the nickle on the P51D, Hellcat, P47 or anything else that used the .50 or was it just for the P51B?



The problems on the P-51B are well noted. However, these problems were almost totally solved within months of the planes deployement through the use of a feed motor scavenged from the Marauder. Once the feed motor was installed the problems were virtually solved - a point that seems to be generally missed. The nickle did not hurt reliabilty much, but it did wear out the gun quite a bit quicker. However, there was no shortage of replacement .50's in the ETO.



Glider said:


> I believe that your view of the .50 against a heavy bomber are flawed. Everyone who took on these aircraft upgunned preferably to 30mm. To believe that the 12.7 would do as well or even close to as well is in my view, very, very, optimistic. Me I would go with 4 x 20.



And none of them mounted EIGHT .50 class guns. I'd probably choose 4 x Hispano's too, but only if I had 200 rpg or more.



Glider said:


> The fusing problems of the 20mm was a real problem early in their deployment. For that reason a number of RAF squadrons originally used all AP as it would do a lot of damage to whatever it hit but this was solved by 1942 when our fused would go off a fraction of a second after hitting the plane doing the most damage.



Actually, a lot of BALL ammo was used by the RAF through 1943. It was not until late 1943 that the superior fused rounds reached the front in significant quantities.



Glider said:


> As for your comment on reliability my second post which presumably crossed covered that point but the results for the British gun would have been a lot better if the ammo hadn't been greased. If our's were bad the USA ones were awfull.



Perhaps. But the jam rate figures I quoted were 1:1500 for the Hispano, which A LOT BETTER right? It is still quite a bit less reliabiable than that of the .50's, which were something like 1:6000 by the end of the war. And given the larger number of guns and ammo supply, and the ability of a .50 to be fired even if it's mate was jammed where the 20mm could not do this, the jam issue is even more signficant.[/quote]



Glider said:


> Spit 9's always had either 2 x 20 plus 4 x LMG or 2 x 20 plus 2 x HMG not just 2 x 20. As for firing the sign of an experienced pilot was using one gun to find the range and then letting fly but this was very rare. Nearly all pilots in all airforces would let fly with everything they had if an enemy was in front of them as tragically it was often the only chance they had.



If you check pilot accounts you will find that this is not true. Most Spit IXc's had 2 of the cannon removed. This allowed more ammo to be loaded in the remaining 2 cannon, and improved the planes performance. Also, the position of the two cannon removed was much more prone to jamming because of the ammo feed.



Glider said:


> The only UK fighter I have found that flew with only 2 x 20 were Hurricane IIc's, which sometimes had two of the guns taken out to improve performance over Malta.



The same was done with the Spit IXc. This was why on later model Spit IX's and XIV the armament was changed back to two 20mm's plus 2 x .50's or 4 x .303's. The issues with the 4 x 20mm setup were not resoved until the Spit Mk.20's came online in 1945.



Glider said:


> Re Rate of Fire. The quoted one is normally 600rpm for the 20mm. The RAF Manual said 650, the test of a Beaufighter was 700 and the test of another plane was 530. None of these firures suprise me as mass production could make them vary by 10-15% of base figure. If you average them you get 620 which is so close to the 600 its not worth arguing about. If you cannot hit the plane with 600 rpm I doubt if you could hit it with 620.
> Personally I would like 2 of those Molins guns please. Then I would happily leave my 4 x LMG or 2 x HMG behind and carry extra ammo.



Well I've seen all kinds of figures thrown about. But actuall tests of in-service aircraft always show RoF's below 600 rpm. When I go home in late January I'll try to find the German test data. However, I'm not disputing the 600 rpm figure for the Hispano, just stating that it is near the maximum. For the .50, 800 rpm seems the reasonable figure to use since the guns came from the factory rated at 750-850 rpm, adjustable by how the headspacing was set, on a new gun.

With the 57mm molins gun you'd be toothless vs. any fighter. It doesn't matter how big the round is if it fails to hit the target.

=S=

Lunatic


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## Glider (Dec 17, 2005)

Lunatic
The first American 20mm was based on the original French Birkigt type 404 and was known as the American M1 and it was this that the USA first manufactured with all the reliability quirks we agree on.
Whilst this was going on the UK which started with the same weapon had developed it into a new version which we called the Mark 2. There were seven main differences between the USA M1 and the UK Mark 2, the main one being the size of the Chamber.
The designs were sent over to the USA in January 1942 with a copy of the improved weapon. The UK was not suprisingly asking for production to be standardised on one model, our Mark 2 as it was far more reliable. Tests were undertaken at Aberdeen, Eglin Field, Wright Field and Kenvil proving ground to test the British suggestions. 

It was agreed on 4th April that further tests be undertaken which were the ones I documented in my posting showing the 5000 round test. Despite these results the US Ordnance Department refused to modify the design of USA built 20mm with regard to the chamber. They even refused to let any USA manufacturer build them to UK standards for use by UK forces.
Heaven only knows why they could come up with such a suggestion when the results were as clear as they were.

The point is that the USA had a 20mm based on the HS404 before the British plans arrived for the modified Mark 2 in January 1942.


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## Glider (Dec 17, 2005)

Moving on as my cat just jumped on the keyboard and wiped the rest of the message.
The P51B never really resolved all its problems as one of the main ones was the flexing of the wings under combat conditions could flex and jam the ammo feeds. The motor helped but didn't resolve all the problems.

The 1 in 1,500 is of course a better figure, but be fair, I was only correcting a mistake that I made. No one is saying that the 20mm was more reliable than the .50 just that it was reliable enough.

Spit 9c's carried the 4 x LMG as well as the 2 x 20. The type 9e carried the 2 x HMG instead of the 4 x LMG of that I am certain. 
You may be getting confused with the type C wing that could carry 4 x 20 but which never did on a Mk 9. The only Spit I know that carried the 4 x 20 in WW2 were a few Spit 5C in 1944 in Europe. This was because they were used for GA work and were the last few in service as the Mk 9 and others were replacing them. The extra 20 mm came in useful against ground targets. 
No Spitfire 9's had Cannon removed to improve performance with the exception of a couple of one off's that had as much weight removed as possible including armour, to reach very high altitude German Recce planes. 

Rate of fire I have no objection to people settling for 800 rpm its not that much more than 750 which is normally quoted, they can very significantly
from gun to gun and its not as if anyone is claiming a massive increase.

Lastly. The Molins I was refering to, was the tweeked Hispano II that I mentioned in the posting with the test results that fired at 1000 rounds per minute. A Spit with 2 x 57 would be lucky to get off the ground even if they could be fitted.


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## Lunatic (Dec 18, 2005)

Some 9c's were outfitted with the "C" armanent - 4 x 20mm's. However, most of the time 2 of the 20mm's were removed in the field as I described above. Check it out some, you will see this was the case.

As for the "DeWilde" ammo being of British orign - does it not seem strange to you that this was a "new" ammo type in 1940 but that IM11 based ammo for the US .50 had been in production for over 5 years? To produce IM11 you need to compress the powdered constituants - 25% Aluminum, 25% Magnesium, and 50% Barium nitrate, to almost the inginition point. To do this successfuly requires the use of an inert gas to prevent undesired ignition at a lower compression level, and a refrigerated environment.

The availability of IM11 was another reason the US felt comfortable with the .50. No other nation (except Britain) was able to produce this kind of incendiary. Germany, the Soviets, and the Japanese all tried. Also, IM11 is relatively light compared to HE, so the wieght in grams is decieving. The volume and the heat generated (4000F) is what is important .

IM11 and IM23 incediaries are self-igniting. They burst upon the second metal surface contacted, which generally maximizes the chances of starting a fire within the target.

=S=

Lunatic


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## Glider (Dec 18, 2005)

Lunatic. For the UK forces the new DeWilde ammunition was a total British development and the person who led the investigation and design was one Major Dixon. 
We also developed a round for the Vickers .50 for use on ships based on the design of the 303 DeWilde called the Mk B 1z Incendiary which was cleared for use in 1939.
Still looking for the 4 x 20 Mk 9. Can I ask if you could give me some guidance. I would like to identify the Squadron as I do a fair amount of wargames and would like to use it. However will need to support my request.


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## Lunatic (Dec 19, 2005)

I believe some 4 cannon IX's flew with the RAF out of malta, alongside the V's. In both cases the armament was reduced to 2 x 20mm cannon.

Also, the RCAF squadrons 421, and other 400 series squadron's flew them (armed with 4 x 20mm) at Normandy, primarily for ground attack.

=S=

Lunatic

PS: Notice no machine gun ports on the pics below


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## Jabberwocky (Dec 19, 2005)

Don't know about the second picture, but the first one appears to be a LF Mk IXe, not a MK IXc.

Couple of give aways;

1. The longer tropical style nose filter; late production (mid 1943). Not fitted to eariler F MK IX

2. Pointed tail; late production (late 1943)

3. Clipped wings; exclusively used on LF Mk IXc and IXe, again late production

4. Short Hispano cannon barrel (the real clincher); only used on type E wings. The type B and C wings have a longer and more narrow barrel covers, with a straight inital protsions then a long tapering nose with a longer exposed cannon tip. The E type cannon covers are shorter and fatter.

So, its probably a Mk IXe, with a .50cal mounted just inboard of the 20mm cannon.


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## Lunatic (Dec 21, 2005)

Jabberwocky said:


> Don't know about the second picture, but the first one appears to be a LF Mk IXe, not a MK IXc.
> 
> Couple of give aways;
> 
> ...



????

It's got a 20mm inboard and a capped 20mm emplacement outboard.


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## Richard_H (Jul 14, 2006)

Lunatic said:


> Check your sources. Britian didn't get serious about replacing the .303 until 1940. Experiance showed them 8 x .303's were not sufficient.
> 
> 
> 
> ...



The Spit IXc Didn't fly without guns, it either flew with 2x Hispano 20mms and 4 x .303 Brownings or 20 x 20mms and 2x .50 cals brownings.

An earlier mark, Mark V (not Va as it was only equipped with guns) but Mk. VB (2 cannons, 4 guns) and VC (4 cannons) often flew with only cannons.
At least i know that the Spit Mk Vc with 4 cannons tended to only fly with 2 because it weighed a lot more with 4 cannons


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## Glider (Jul 15, 2006)

Richard_H said:


> The Spit IXc Didn't fly without guns, it either flew with 2x Hispano 20mms and 4 x .303 Brownings or 20 x 20mms and 2x .50 cals brownings.
> 
> An earlier mark, Mark V (not Va as it was only equipped with guns) but Mk. VB (2 cannons, 4 guns) and VC (4 cannons) often flew with only cannons.
> At least i know that the Spit Mk Vc with 4 cannons tended to only fly with 2 because it weighed a lot more with 4 cannons



To a degree I believe you to be correct but I have little doubt that some changes were made in the field. 

For instance, the 303 was of little if any good against German Aircraft. If you accept this, then there is no reason why you shouldn't take them out as they are simply dead weight. I am not saying this was common particually late in the war when GA was often the mission, but it wouldn't suprise me if some pilots had them removed.


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## Tony Williams (Jul 16, 2006)

To return to the original subject, this article examines the US choice of fighter armament: CANNON OR MACHINE GUN

Tony Williams: Military gun and ammunition website and discussion forum


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## Twitch (Jul 16, 2006)

This has been discussed in so many other later topics why did this guy revive an 8 month old thread?


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## the lancaster kicks ass (Jul 17, 2006)

newbe.......


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## MacArther (Aug 8, 2006)

Maybe he's a n00b, or maybe....HE LIKES MY POSTS!! HE REALLY DOES!!! YAYYYY


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## Twitch (Aug 9, 2006)

Yeah let's just make a post on this topic once a month just for shitts and giggles.


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## MacArther (Aug 9, 2006)

OK, if you insist.


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