Why no heavier RAF machine gun calibres? (1 Viewer)

As has been established, the RAF's pre-WWII testing found there to be no net benefit to moving to 0.5 in machine guns. This means that the RAF did consider and then rejected 0.5 in MG based on evidence. Conversely, the US found the 0.5 in to be about 1/3 as effective as the 20 mm yet the first two generations of USAAF/USAF jet fighters used 0.5 in MG until they were demonstrated inadequate in Korea.

Instead of berating the RAF over not going to 0.5 in MG, maybe we should start the same level of discussion for the USAAF/USAF retention of it.

swampyankee said:

Instead of berating the RAF over not going to 0.5 in MG, maybe we should start the same level of discussion for the USAAF/USAF retention of it.

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Finally, a fresh topic that has never before been debated on forums!

Engineman said:

Nope, I don't accept that it was impossible to develop a good working MK 213 C clone in a shorter timescale.

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The USA's clone of the V-1 was a real missed opportunity. By Korea we could have had air-launched examples with precision radio and/or radar guidance.

swampyankee said:

As has been established, the RAF's pre-WWII testing found there to be no net benefit to moving to 0.5 in machine guns.

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But in 1944 the RAF realized it had 'effed up and badly needed fighter bombers that would not terrorize not only the Germans but their own pilots. So they pushed hard to replace the four .303 Brownings in Spitfires with .50 cal guns.

PAT303 said:

Do you think maybe the reason for the Mk VIII part numbers being original and also being on the Mk XIV drawings could be because they went into production where's the Mk III didn't?, furthermore all the drawings and documentation for it were destroyed in September 1940 so there's no logical reason for any of the prototype Mk III numbers to be used on a later production variants.

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If you had actually spent any time in the aviation industry (and I have been in the industry since 1963) OR if you had even the vaguest idea of 1940s British aviation Quality Control you would understand why your suggestion is so laughable.

And on a practical note - why would they waste time and take all the Mk III drawings and renumber them for a later model but never renumber any of the Mk I, IA, II, etc drawings used on later model aircraft?

ThomasP said:

The Spitfire Mk III was the Supermarine model number 330.

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Thank you ThomasP.

Thank you also NZTyphoon for the history on the model 330 and the reason for the shortage of 330 drawings. Presumably they stripped down the tail gear, and probably other items, and redrew them or, more likely with the tail gear, retrieved copies from the contractor(s) who built the strut and other parts. I would have expected some of the shadow factories to have also had copies of many of the model 330 blueprints but maybe they had not yet been distributed to many sub-contactors and shadow factories.

I only have one 330nn blueprint (33026-109). Area 26 is what Supermarine called "tail skid" meaning, on later aircraft, tail landing gear.

Know knowing that the Mk III was the model 330 I opened my very poor quality Mk XIX parts list and found that some of the parts contained in the tail strut and attached parts were from the Mk III and that a fair percentage of the parts for the tail strut had been replaced with parts from the model 337 and 351 aircraft which proves that the Mk III tail leg had substantial deficiencies and needed upgrade, though to a far lower extent than the fuselage stern which has no model 330 parts in the blueprints I have. THat as mentioned above is probably due to the burnt blueprints.

Engineman said:

I guess that the real problem was a lack of appreciation that a better gun than the 0.5 was required. Is this the same story as why the British stuck with 0.303 and, why didn't the British just fit 0.5's?

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Maybe you should go back to the start of the thread, the reason why the RAF stayed with the .303 instead of using the .50 BMG has been discussed and proven numerous times.

SaparotRob said:

Aw c'mon. We hadda have something better than the Botha.

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In the autumn of 1939? Nothing I can think of.

MiTasol said:

If you had actually spent any time in the aviation industry (and I have been in the industry since 1963) OR if you had even the vaguest idea of 1940s British aviation Quality Control you would understand why your suggestion is so laughable.

And on a practical note - why would they waste time and take all the Mk III drawings and renumber them for a later model but never renumber any of the Mk I, IA, II, etc drawings used on later model aircraft?

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There was no Mk III drawings because everything associated with it was destroyed when the factory was bombed which added to the many reasons why it was cancelled. The Mk III design was going to be the development line for the Spitfire but the war started so the interim models got the go ahead instead, remember that in all 1200 Mk III's were ordered so it's clear the direction the Spitfire line was taking.

PAT303 said:

Maybe you should go back to the start of the thread, the reason why the RAF stayed with the .303 instead of using the .50 BMG has been discussed and proven numerous times.

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Agreed.

The British also had the Vickers .50 which was about as developed as the Browning .50 at the time so it was also bypassed for the Hispano.

PAT303 said:

There was no Mk III drawings because everything associated with it was destroyed when the factory was bombed which added to the many reasons why it was cancelled. The Mk III design was going to be the development line for the Spitfire but the war started so the interim models got the go ahead instead, remember that in all 1200 Mk III's were ordered so it's clear the direction the Spitfire line was taking.

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Not everything as demonstrated in my earlier post today.

MIflyer said:

But in 1944 the RAF realized it had 'effed up and badly needed fighter bombers that would not terrorize not only the Germans but their own pilots. So they pushed hard to replace the four .303 Brownings in Spitfires with .50 cal guns.

View attachment 811669View attachment 811670

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Where were the British going to get these wonder weapons? The Americans showed surprising little interest in the "WEAPON THAT WON WWII" until after the shooting started..



The reality is that the pre war US Army wasn't interested in the 50 cal.
From HyperWar: The Machine Gun (Vol. I/Part V) (The bold is my emphasis):

Browning Aircraft Machine Gun, Caliber .30

"During the period from 1927 to 1930 when Wright Field, Springfield Armory, and others continued to work on a light caliber .30 highspeed aircraft machine gun, no concise requirements had been prepared for inclusion in an official specification to cover military characteristics. These facts, as shown by the record, indicate considerable controversy as to what was wanted. When a real demand was shown in 1929 for such a gun to perform under the approved military demands, the Colt's Co. brought out the fully developed right- and left-hand feed gun that was later standardized as the Browning Machine Gun, Caliber .30, M2."

"It is indeed fortunate that this work was done at the time, as practically all machine gun development stopped shortly afterwards, that is, as far as the United States was concerned. It was partly due to lack of funds but more from the peaceful lethargy that invariably settles on this country after each war. In 1938 the caliber .30 Browning gun, better known as the B. A. M. G., was still being made in very limited quantities with the same specifications as the original Model M2. As a larger caliber machine gun was still looked upon by the Air Force as a special objectives weapon, the caliber .30 was its first-line machine gun for both fixed and flexible mounting as late as 7 December 1941."


Browning Caliber .50 Aircraft Machine Gun
"The barrel of the water-cooled gun extended some 2 inches forward of the water jacket, which resulted in the muzzle becoming overheated when long bursts were attempted. The light barrels used on the aircraft caliber .50 machine guns also caused overheating after relatively short bursts. The weapon's limitations revealed in the early service trials of the water-cooled version raised a serious doubt with the Army and Navy during the period from 1927 to 1933 as to its potential worth either as an aviation gun or for antiaircraft use."

"No requirements were forthcoming prior to 1933 for an improved type of caliber .50 machine gun."

"The Ordnance Department lacked funds in the period from 1927 to 1933 (as evidenced by the fact that not a single machine gun was manufactured in 1928) to undertake the development and production of a new type of caliber .50 gun for two basic reasons:
(a) The depression severely curtailed available funds.
(b) No requirement had been established for the development or manufacture of such a series of guns."

"During 1932 Gen. Samuel Hoff, Chief of Ordnance, Army, after observing concentrated activity on Dr. Green's part day after day, jokingly asked for an explanation. He replied that an attempt was being made to solve a problem having great bearing on the future of the caliber .50 machine gun, even though no requirement had been presented to the Ordnance Department."

As usual the Navy came to the rescue.

"The Army, in 1933, without funds to carry forward the development of a complete series of new caliber .50 machine guns, interested the Navy in the results of the previous tests of both the aircraft and antiaircraft, water-cooled models."

"Further conferences were held with Commanders Sherman and Mahoney, who took the matter up with Admiral E. B. Larimer, Chief of the Bureau of Ordnance, Navy. The latter not only approved assistance in further research on aircraft and antiaircraft caliber .50 M2 machine guns but authorized an immediate expenditure in 1932-33 of approximately $150,000 to be used in the development and supply to the Navy of as many weapons as possible with the funds available. The Navy placed orders early in 1933 with the Ordnance Department of the Army for the manufacture by Colt of the basic M2 type improved caliber .50 machine guns. "

Meanwhile at the same time the Hispano Suiza was also being developed
"Chapter 14
Birkigt Type 404 20-mm (Hispano-Suiza) Cannon"

"In 1933 Birkigt began work on the devisement of a weapon he later produced successfully. This mechanism could in no sense rise to the dignity of an invention, the principles involved having been long known by those who followed the profession of gun design. A combination of already established methods of operation was arranged in such a manner as to result in a shooting."

"Upon hearing of the successful manufacture of this automatic: cannon with its unusually high rate of fire, the French Air Ministry notified the Hispano company that no other country could be offered the weapon without its approval. Three countries, England, Russia, and Czechoslovakia, learning of experimental results through their military attachés, began to make overtures to the Hispano-Suiza company to purchase the cannon for testing purposes.

A rumor that a 23-mm version was sold to Russia without the consent of the Air Ministry placed the whole project practically under secret status. It was charged and denied on the floor of the Chamber of Deputies that the Russian sale had taken place. The Czechoslovakian Commission was unable to obtain official Government sanction to buy the gun and not until the fall of 1936 were British representatives permitted to see it in action.

The men given this privilege were Group Capt. C. H. Keith. R. A. F., and Christopher Bilney, Chief of the Operational Requirements Branch, who were invited by Hispano-Suiza to witness the function firing of a Birkigt automatic 20-mm aircraft cannon. This weapon had been designed for engine installation, since the company was the original promoter of this system of mounting. A firing range had been improvised in an ancient fort at Bouviers, where the new cannon was mounted alongside an Oerlikon. The latter was fired first with creditable results. Then the Birkigt gun was fired and its amazingly high rate, estimated at 700 rounds a minute greatly impressed the British officers. Upon request the parts were disassembled before them, and attention was called to the small number of operational components, and their simple but rugged construction."

The gist of all this is that the fabled Browning M2 was less advanced in its development when the British made the correct decision to select the 20mm Hispano as their weapon of the future.

Reluctant Poster said:

The gist of all this is that the fabled Browning M2 was less advanced in its development when the British made the correct decision to select the 20mm Hispano as their weapon of the future.

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This is actually somewhat debatable. Dates are really important. Also what was actually achieved in certain dates. Not the British were not correct but where each gun was in it's development is a lot more complicated. The British did little or no testing after the early trials and were in no position, correctly or incorrectly to judge the state of development of the .50 cal gun.

The British, for instance in their 1928(?) trial were not testing the .50 cal M2. They were testing the M1921 (or a commercial 1924?). The M2 was not adopted until 1933. The M1 Version never existed except on paper. It was supposed to be able to change from left feed only to either left or right feed. Before this change could be implemented they also changed a number of other things. And we have the difference between the developmental guns and the "standard" M2 which didn't exist (formal adoption with all/most changes).
Let's also remember that in the early 30s the Army was so short of funds that not only did they ask the Navy to handle the .50 cal gun project, they asked the Navy to order several Allison V-12s as airship engines to keep the basic engine alive.
Unless somebody has evidence to contrary when the British made their decision in 1936-37, they had not tested or observed any trials of the M2 gun in 1933-36.
I am not saying that they would have changed their minds if they did but there were 7-8 years between the British trials at their own test site and the observation at the Hispano test site.
The 1928 tests by the British were for water cooled guns. By 1933 there were both water cooled and air cooled .50cal and there were two different barrel lengths and there were different weight barrels depending on intended use. They had arranged for the left and right had feeds and solved some ( but not all) of the problems of the 1928-30 guns.

Now maybe there was a British attaché in the US that was giving reports to the British during the 1930s but no reports so far in the popular press.

And even better guns doesn't solve the ammo problem. All during the 1930s the US was using the M1 ball (or M1 AP) round in the Brownings and for all practical purposes that just meant they were firing a heavier bullet at the same speed as the .5 in Vickers. Anthony Williams makes one of his few mistakes in his article on the .5in Vickers when he says" The Browning was designed around a longer and more powerful cartridge (12.7x99 instead of 12.7x81) which typically fired bullets weighing 710 grains (46 g) at 2,900 fps (880 m/s), generating around two-thirds more muzzle energy. A report, dated 1928, of the tests by the Admiralty of the water-cooled versions of the guns has survived." These are the ballistics for the M2 Ball and AP rounds which did not show up until 1940-41. The 1928 ammo used a heavier bullet at about 2500fps. A lot closer in energy to the .5in Vickers. It also means that in 1936 the 20mm Hispano is a lot more powerful per round than the early 1930s cal ammo, and the Hispano is offering exploding shells. The US is not and the British didn't use exploding shells in the Vickers either.

Now it turns out that the big Browning had a number of problems in the field as an aircraft gun in 1940-41. Testing had NOT been good enough. Testing had been done short belts (100 rounds or under?), little or no Gs being pulled when firing, little or no high altitude firing. But the Hispano in British service1940 may not have been trouble free either. Even in the Beaufighter, and it was limited to the 60 drum for a while.

The US improved the M2 .50 cal but they never changed the designation. The M2A1 shows up well after WW II, like 2010.
The AN/M2 aircraft gun had several changes but exactly when they showed up? This has the increased rate of fire and it changed the cam track for the feed pawl which roughly double the amount of pull the gun exerted on the belt for feeding. Not a sure cure but it helped. Not sure if the change in the belt pull made it into the ground guns. However it is supposed to be possible to change any version of the M2 (water cooled AA gun, ground mount heavier barrel, short barrel aircraft gun) to any other if the appropriate parts are available. Just swap parts, no cutting, no filing.

I would also note in the chart that only 50 of the M3 fast firing guns are listed. This may be correct but there were over 8,000 T number guns built for combat trials.

Reluctant Poster said:

Three countries, England, Russia, and Czechoslovakia, learning of experimental results through their military attachés, began to make overtures to the Hispano-Suiza company to purchase the cannon for testing purposes.

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Pedantic trivia, but England was not a country. A nation certainly but not a sovereign country since 1707. More than seventy years before the United States became a sovereign country. Britain, however, was a sovereign country. As an Englishman I am sensitive to the use of England as an inaccurate synonym for Britain or the United Kingdom.

yulzari said:

Pedantic trivia, but England was not a country. A nation certainly but not a sovereign country since 1707. More than seventy years before the United States became a sovereign country. Britain, however, was a sovereign country. As an Englishman I am sensitive to the use of England as an inaccurate synonym for Britain or the United Kingdom.

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Take it up with the author I am only quoting

Shortround6 said:

This is actually somewhat debatable. Dates are really important. Also what was actually achieved in certain dates. Not the British were not correct but where each gun was in it's development is a lot more complicated. The British did little or no testing after the early trials and were in no position, correctly or incorrectly to judge the state of development of the .50 cal gun.

The British, for instance in their 1928(?) trial were not testing the .50 cal M2. They were testing the M1921 (or a commercial 1924?). The M2 was not adopted until 1933. The M1 Version never existed except on paper. It was supposed to be able to change from left feed only to either left or right feed. Before this change could be implemented they also changed a number of other things. And we have the difference between the developmental guns and the "standard" M2 which didn't exist (formal adoption with all/most changes).
Let's also remember that in the early 30s the Army was so short of funds that not only did they ask the Navy to handle the .50 cal gun project, they asked the Navy to order several Allison V-12s as airship engines to keep the basic engine alive.
Unless somebody has evidence to contrary when the British made their decision in 1936-37, they had not tested or observed any trials of the M2 gun in 1933-36.
I am not saying that they would have changed their minds if they did but there were 7-8 years between the British trials at their own test site and the observation at the Hispano test site.
The 1928 tests by the British were for water cooled guns. By 1933 there were both water cooled and air cooled .50cal and there were two different barrel lengths and there were different weight barrels depending on intended use. They had arranged for the left and right had feeds and solved some ( but not all) of the problems of the 1928-30 guns.

Now maybe there was a British attaché in the US that was giving reports to the British during the 1930s but no reports so far in the popular press.

And even better guns doesn't solve the ammo problem. All during the 1930s the US was using the M1 ball (or M1 AP) round in the Brownings and for all practical purposes that just meant they were firing a heavier bullet at the same speed as the .5 in Vickers. Anthony Williams makes one of his few mistakes in his article on the .5in Vickers when he says" The Browning was designed around a longer and more powerful cartridge (12.7x99 instead of 12.7x81) which typically fired bullets weighing 710 grains (46 g) at 2,900 fps (880 m/s), generating around two-thirds more muzzle energy. A report, dated 1928, of the tests by the Admiralty of the water-cooled versions of the guns has survived." These are the ballistics for the M2 Ball and AP rounds which did not show up until 1940-41. The 1928 ammo used a heavier bullet at about 2500fps. A lot closer in energy to the .5in Vickers. It also means that in 1936 the 20mm Hispano is a lot more powerful per round than the early 1930s cal ammo, and the Hispano is offering exploding shells. The US is not and the British didn't use exploding shells in the Vickers either.

Now it turns out that the big Browning had a number of problems in the field as an aircraft gun in 1940-41. Testing had NOT been good enough. Testing had been done short belts (100 rounds or under?), little or no Gs being pulled when firing, little or no high altitude firing. But the Hispano in British service1940 may not have been trouble free either. Even in the Beaufighter, and it was limited to the 60 drum for a while.

The US improved the M2 .50 cal but they never changed the designation. The M2A1 shows up well after WW II, like 2010.
The AN/M2 aircraft gun had several changes but exactly when they showed up? This has the increased rate of fire and it changed the cam track for the feed pawl which roughly double the amount of pull the gun exerted on the belt for feeding. Not a sure cure but it helped. Not sure if the change in the belt pull made it into the ground guns. However it is supposed to be possible to change any version of the M2 (water cooled AA gun, ground mount heavier barrel, short barrel aircraft gun) to any other if the appropriate parts are available. Just swap parts, no cutting, no filing.

I would also note in the chart that only 50 of the M3 fast firing guns are listed. This may be correct but there were over 8,000 T number guns built for combat trials.

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I re read my post and realize I lost my main point in all the verbiage. I didn't intend to imply that the British actually evaluated the Browning 50 cal. The point is that they had nothing to evaluate. The 50 cal simply wasn't in a fit state.
A general theme (not yours) seems to be is that the British were fools to adopt the Browning 30 cal that they should have gone to the Browning 50 cal. The reality the Browning 50 cal was a pipe dream at the time.

An excerpt from an article in the July-August 1944 issue of Army Ordnance showing the changes made to the Browning 50 cal to make it easier to produce.