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

[102first_hussars]

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.

 

[DerAdlerIstGelandet]

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.

 

[Jabberwocky]

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.

 

[DerAdlerIstGelandet]

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.

 

[Jank]

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.

 

[DerAdlerIstGelandet]

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.

 

[Glider]

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.

 

[evangilder]

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.

 

[Jank]

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.

 

[Glider]

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

 

[Jank]

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.

 

[Lunatic]

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.

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

 

[Lunatic]

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

 

[Jabberwocky]

""
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.

 

[Glider]

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

 

[Glider]

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.

 

[Lunatic]

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.

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

 

[Lunatic]

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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

 

[Jabberwocky]

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.

 

[MacArther]

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!