0.50 Browning MG and it's descendnats for 'other' air forces?

[Shortround6]

Perhaps the FN factory and customers had different standards than the US ordnance dept? It took the US until mid-late 1944 to get the big Browning up to 1200rpm with acceptable numbers of jams, parts breakage and gun/barrel life. If you accept a higher number of jams and lower number of rounds between parts failures you may be able to get the higher rate of fire without too much trouble.

 

[Vincenzo]

or could have higher standard in the production

 

[Shortround6]

The US had at least three different companies working on the high rate of fire .50 cal gun and each company went through multiple prototypes/versions. It took about 3 years from start of work to to get an acceptable model (the US Standards) and the version chosen had next to NO INTERCHANGEABLE PARTS with the M2 gun. It wasn't simply a lighten bolt and different spring. The High rate of fire guns had to be manufactured as such and no conversion kit to bring older guns "up to speed" was ever issued.

Some of the American prototypes were much more successful than others and it wasn't a steady progression in rates of fire, some prototypes may have simply shown them what not to do.
The US had decided it wanted 1 breakage and 5 malfunctions per 5,000 rounds fired at 1200rpm which may have been setting the bar a bit too high. The Russian 12.7mm machineguns were not designed to last for 5,000rounds without hte whole gun be replaced.
see: page 4 and on.
http://photos.imageevent.com/badgerdog/generalstorage/georgemchinnthemachinegun/TheMGV3a.pdf

The American .50 was also a barrel burner. Long bursts could take out some of the rifling. Even the 800rpm guns were supposed to be limited to initial 75 round bursts and then shorter bursts. And I believe this was with chrome lined barrels.

A bigger bore will help with barrel life.

Edit> The malfunction/breakage rates may be for the gun/s on a test range. Relatively clean and moderate temperature. Throw in widely varying temperatures, some dust/dirt/grit and trying to fire while turning ( 3-5 Gs holding ammo belts into the bottom of the ammo trays/boxes and rates of fire and malfunction can vary considerably. The Pre-war American .50s didn't meet their 'advertised' rates of fire either. Too much testing had been done with short belts and long belts, especially under "G" loads slowed the guns down if not causing malfunctions. As noted in the link, at some point even the pre-1200rpm guns were modified to roughly double their belt pull/lift capacity.

 

[kool kitty89]

As a general rule of thumb the weight of the of the projectile varies with the cube of the caliber. This assumes similar construction, materials and shape. A 13mm projectile will be roughly 4 times heavier than a 8mm projectile and a 20 mm projectile will be 4 times heavier than a 13mm projectile or 16 times heavier than an 8mm projectile. Simple theory gets thrown several curves (complications) in that the 8mm projectiles often have sizable components of lead in them while the larger ones do not. Steel having a rather lower density than lead. HE and pyrotechnical compounds have a much lower density than either. Wall thickness of the hollow projectile doesn't scale well. You need a certain minimum thickness for strength, both for centrifugal force (projectile spin) and to keep the pressure on the base of the projectile when firing from buckling the projectile in the barrel. This means, for practical purposes until the German mine shell, that projectile capacity did NOT change with the cube of the diameter but increased at a much faster rate. You don't need a much thicker shell wall on a 20mm projectile than you do on a 13-15mm projectile.

Yes, also all reasons a shorter, wider projectile would be more useful for chemical filler than a longer, smaller caliber one of similar mass. (space occupied by fuzing components would be part of that too)

On top of that, larger barrels have better wear properties, the drawbacks being heavier barrels and lower sectional density of the projectiles. (ammunition may or may not be heavier as well, that would depend more on the projectile weight, case weight -if any dimensions change, and propellant charge)

Something in the 14-17 mm range wouldn't be as good as 20 mm for HE/I but still considerably better than 12.7 mm, and even 13.2 mm would have some noticeable advantages over 12.7 mm. (larger caliber, shorter projectiles would probably be preferable on the whole -say around 17 mm with similar proportions to the Ho-5 or Shvak shells, though AP performance would diminish at range due to poorer ballistics even if velocity didn't drop)

a lot depends on timing, at certain times the Oerlikon guns required lubricated ammo (read greased or at least wax coated) which was frowned on for aircraft use. Grease/wax at 60 degrees F vs Grease/wax at minus 30-40 degrees let alone 60 degrees below. What is tolerated aboard ship/s is not tolerated as much in aircraft or on land. Please remember that while war was looming they weren't shooting just yet and what was desirable often held more importance than it did once the shooting started. Different countries may have had different standards of reliability.
Please remember too, that in the case of Great Britain, they were not buying just for use in the British isles but for use through out the Empire. ANY gun or ammo had to tolerate a wide range of climatic conditions.

Indeed, and there may be a better argument for some other countries adopting the oerlikon gun (plus cases of engine mounted guns would avoid some of the temperature related grease/wax issues).

The Oerlikon guns may have been more appealing in the US, especially for the USN given the typical low to medium altitude use and climates usually in play. (USAAC aircraft focusing mainly on coastal conditions would tend to fare better there too) Part of that is in hindsight given the awful trouble the hispano gave in US service, but the more practical pre-war advantages of lighter, lower recoil weapons intended for wing mounting would be significant as well. (especially with the USN more desperate for converting to 20 mm) The FFF may have been unattractive, but the FFL would be in a fairly reasonable performance range. (much better than the Army's M4 37 mm gun and similar to the ballistics of the 23 mm Madsen -slightly higher velocity but lower sectional density)

That said, larger caliber developments of the M2 Browning was probably the bigger missed opportunity. (also hindsight, but given the bureaucratic issues tied to US 'cannon' -guns above .60 cal- being manufactured with looser -artillery- tolerances, not only might the Oerlikon mechanism have fared better, but any light cannon staying at or below .60 cal would also avoid that problem and have tolerances akin to the .50)

There is a lot of talk about re-chambering and necking out (or down). Some of these guns had a few MM to spare as far as overall cartridge length goes and some did not. The designation, such as 23 X 106 does not tell you the over all length of the round, it tells you how long the cartridge case is without projectile. It also does not tell you haw fat the case is (diameter of the body of the case). It sometimes tells you how the gun was headspaced (how the cartridge is located in the chamber front to back) The 20mm Hispano case was 24.8mm in diameter and headspaced on the shoulder.

The Madsen 23 mm round was of similar length to the 20x120mm madsen round and I'm not sure on the exact dimensions, but I wasn't expecting it to directly fit into the Hispano, more suggesting that the hispano mechanism be adapted for a new 20 mm gun to replace the older madsen OR that the 20x110mm hispano ammunition be necked out to accommodate the 23 mm Madsen shell at some expense of velocity and possibly reduced propellant charge. (similar compromises to the MG-151 going from 15 to 20 mm)

But that assumes any country could secure a license for even the Madsen shells (particularly the high capacity HE/T rounds with self-destruct). It may have been just assumptions on continued import access to Denmark, but the lack of licensed production does imply the possibility of Madsen's terms being unfavorable or licenses not being offered at all. (granted, reverse engineering the weapons or ammunition could also have been a possibility, particularly after Denmark's capture)

In the case of the Browning, a 23 mm gun scaled up and engineered for the 23x106 mm round, or perhaps adapting the high powered US .60 cal anti-tank case instead would have been useful. (but that just goes back to the broader potential for the Americans to focus on the browning in general ... including scaling it up to fire that powerful .60 cal round in the first place -they went to the trouble of copying the MG-151, but didn't work on scaled up browning derivatives?)

Beyond that, the 'simple' cases of barrel replacements to otherwise similar guns would involve using identical maximum case diameters and base dimensions as well as projectile length/seating that maintained similar overall cartridge length. (so similar to the way the .50 BMG was adapted to 13.2 mm Hotchkiss and 14.3 mm in the .55" Boys)

The taper on the .50 cal Browning case is there for a reason, so is the shoulder. They can be changed but eliminating them or reducing them to mere vestiges of what they were is going to play havoc with the guns ability to function without some major development time.

I wasn't suggesting the taper be adjusted, though going much/any wider than the Boys did would mean a more significant change to the shoulder's position or dimensions. But wouldn't the 14.3 mm projectile of the Boys round itself be reasonable to adapt to the existing M2?

15~15.2 mm (60 cal) might have been doable, but the difference between neck and shoulder diameter would be even smaller and might cause problems. (likely widening the neck to 16.2~16.4 mm with the shoulder still at 18.1 mm, that's not much taper) A 17 mm or larger projectile would be a more definite problem and require repositioning of the shoulder and likely more modifications to the gun.

Looks like the Oerlikon FFF fired a 128 g shell at 600 m/s, the Ikaria MG FF fired the 134 g shell at same speed? The muzzle energy was 23-24 kj. For a 100 g projectile, that would be close to 700 m/s? The MG FFM used a bit smaller propellant charge, the 92 g shell went out at 700 m/s.
The MG FF didn't ended nearly as heavy as the FFL, but FFL received more development that gradually decreased it's weight from 43 to 34 kg, later to 30 kg. The development of the FFF/MG FF wasn't much pressed on, the only modification being the MG FFM, so the lower recoil could still operate the gun action. The FFL would be as easy/hard to install on the turets as MG 151 or Hispano V?

The lighter, developed form of the FFL combined with the lower recoil and shorter barrel should have made it more practical as a defensive weapon than the Hispano, though bulkier than the M2.

Since there is a violent opposition for the UK adoption of the 'big bang' Browning ( ), any opinion on how well would it served in LW or USAF/USN?

As above, the US adopting the Boys (or even Hotchkiss) round would be interesting, but more so would be the powerful American .60 cal round. The latter wouldn't be rechambering though, but a complete scaling up of the weapon more akin to what the Japanese did, but likely heavier than the Ho-5 given that .60 cal was considerably more powerful, more powerful than the German 15 mm cartridge as well. (whether they kept it 60 cal or necked it out would be another matter ... or a matter of /when/ as well, given they did just that for the M39 revolver cannon much later)

 

[kool kitty89]

The FN-Browning was variously advertised at rates of 1000 rpm, 1050 rpm, 1100 rpm and 1200 rpm throughout the 1930s, so I wouldn't view the rate with too much suspicion. The most common figure I've come across is the pre-war literature is 1050 rpm, which is the rate the RAF got when they tested the gun in 1938.

I would consider 1200 rpm to probably be the upper end of the cyclic limit for the gun. A maximum value, rather than an average value.

The Finns also put a locally built version of the M2 Browning on their Brewster Buffalos and the VL Myrsky. The gun is recorded in Finnish sources as firing at 1000-1100 rpm, further lending credence to the notion that the Browning was capable of being uprated to more than 1000 rpm.

That might explain the preference for synchronized guns with the Finns and some smaller airforces when the American synchronized brownings fared rather poorly in rate of fire. Even if sustained high rates led to problems on the M2, use of higher peak cyclic rates combined with the limits of synchronization may have made for a fairly useful weapon.

The US had at least three different companies working on the high rate of fire .50 cal gun and each company went through multiple prototypes/versions. It took about 3 years from start of work to to get an acceptable model (the US Standards) and the version chosen had next to NO INTERCHANGEABLE PARTS with the M2 gun. It wasn't simply a lighten bolt and different spring. The High rate of fire guns had to be manufactured as such and no conversion kit to bring older guns "up to speed" was ever issued.

Any idea how that compared with the American development of the Hispano? I know it had some particularly convoluted problems both on the engineering end (including ignoring British suggestions) and manufacturing tolerance end.

Some of the American prototypes were much more successful than others and it wasn't a steady progression in rates of fire, some prototypes may have simply shown them what not to do.
The US had decided it wanted 1 breakage and 5 malfunctions per 5,000 rounds fired at 1200rpm which may have been setting the bar a bit too high. The Russian 12.7mm machineguns were not designed to last for 5,000rounds without hte whole gun be replaced.

Though that sounds more like the opposite of some problems the Hispano had ... setting higher standards and tighter tolerances than the 'artillery' class cannon. (of course, the 37 mm M4 was a fairly reliable weapon in spite of being in that same class, if more conservative engineering than the Hispano itself, and a fairly poor performer for its size and weight)

The American .50 was also a barrel burner. Long bursts could take out some of the rifling. Even the 800rpm guns were supposed to be limited to initial 75 round bursts and then shorter bursts. And I believe this was with chrome lined barrels.

A bigger bore will help with barrel life.

As above, allowing high peak rates of fire exclusively in synchronized mounts (where average/effective RoF would still be within practical wear tolerances) could be significant. And yes, I mentioned before that larger caliber projectiles would improve barrel wear and would have been advantages to using the Hotchkiss and especially Boys rounds. (in the latter case using the special high energy high velocity propellant loadings might not be compatible with the existing M2, but more moderate loadings of the same cartridge should at least be more straightforward)

 

[Shortround6]

There was an experimental 16mm round based on the .50 cal. It was used in an experimental Cannon/machinegun in the 1939-42 period and was of interest to Lockheed for the P-38.

From Tony Williams website. Photo shows a variety of cases derived from the .50 browning.

The gun/ammo was rejected by the Air Force. Details seem to be scarce to non-existent. 16mm seems to be about the max that could be reasonably put in a .50 cal case for use in an automatic weapon.

Part of the caliber question comes to philosophy or school of thought. The US wanted high velocity for short times of flight and depended on kinetic energy for destruction. Other nations wanted the exploding projectile and were willing to take lower velocity. The Hispano (or guns of that size and power) could combine both. The US went off the deep end and spent waaay to much money and time on extra high velocity .50 cal and .60cal guns.

The Browning could certainly be scaled up to take larger rounds as the Japanese well showed with 30mm Browings (weighed 60kg or over) But again it depends on what the guns are wanted for. Fixed gun for fighter use or turret mount gun for bomber defense ( and in 1937-39 ONLY the French and British had turrets in service) and turrets ranged from the 30in dia (900mm) one on the Blenheim to the large 20mm turrets on the French bombers (trying to change the drum on the Hispano in combat with the drum outside the turret would have been interesting.

You aren't going to gain much of anything going from 12.7mm to 13.2 or even 13.9mm. Not enough to show any real difference. In some cases the change in caliber was for manufacturing convenience. Suiting the cartridge and gun to existing ammo production equipment. Nations using 13mm Hotchkiss machine guns could use the same bullet making equipment and the French changed things sometimes just for the sake of changing them so they would be different. The French were in the top 3-4 of weapons exporters between the wars.

 

[kool kitty89]

There was an experimental 16mm round based on the .50 cal. It was used in an experimental Cannon/machinegun in the 1939-42 period and was of interest to Lockheed for the P-38.

From Tony Williams website. Photo shows a variety of cases derived from the .50 browning.

The gun/ammo was rejected by the Air Force. Details seem to be scarce to non-existent. 16mm seems to be about the max that could be reasonably put in a .50 cal case for use in an automatic weapon.

Given the rebated rim on that round (16x99RB listed here CALIBRE GROUPS ), I'd hazard a guess at that round being intended for an API blowback weapon.

Part of the caliber question comes to philosophy or school of thought. The US wanted high velocity for short times of flight and depended on kinetic energy for destruction. Other nations wanted the exploding projectile and were willing to take lower velocity. The Hispano (or guns of that size and power) could combine both. The US went off the deep end and spent waaay to much money and time on extra high velocity .50 cal and .60cal guns.

There's also the odd case of the slow firing, low velocity 37 mm M4, and a complete lack of any middle ground between the .50 browining and Hispano and bulky, slow firing, low velocity M4.

Why the USAAF was willing to compromise on the M4 and even seriously consider it a capable air to air weapon and even continue its development is a bit bizarre given the apparent obsession with velocity. (it's also one case where the low velocity was a serious complain from pilots using it, particularly with its mis-matched trajectory with the .50s and .30-06 rounds carried alongside it on the P-39)

In the mid/late 1930s the US Ordinance Department did pursue 23 mm cannon development with a number of designs:
CAL90

Interestingly, it's mentioned that Colt proposed adapting the short recoil Browning machine gun mechanism to the 23 mm (.90 cal) requirement, but that proposal was rejected. The low (130 RPM) cyclic rate is also rather strange. The (apparently) API blowback based T2 cannon seems to have been the most promising with a rate of fire close to that of the Oerlikon FFS (400-450 rpm) and somewhat better than the Madsen's 360 rpm.

The rate of fire, weight, and caliber requirements were all met by the Madsen cannon itself, though the 869 m/s muzzel velocity was no. (the 23 mm madsen only managing 720 m/s -still far better than the M4's 610 m/s)


Aside from that, looking at the 20x110 hispano and 20x120 madsen rounds side by side here:
http://www.quarryhs.co.uk/20mm2.jpg

It seems like it might actually have been more straightforward than I was thinking to adapt the madsen cartridge to the hispano, or the 23 mm madsen shell to the hispano cartridge.

 

[Shortround6]

The US was certainly interested in bigger guns than the .50 cal. It just takes 4-6 years to go from the start of a project to getting a working gun into production and that assumes the thing was going to work to begin with. Since high rate of fire guns depend on a balance of bullet weight, propellant, cartridge length, gun weight (and component parts) and often cam surfaces (belt feed mechanisms often depend on a stud traveling in a track to turn the forward and back motion of the bolt into a sideways motion to pull the belt), even quality of the brass (or steel) cases. getting everything to work together at the desired speed often takes a while. Firing single shots is often no problem

The US had built several of the largest prototype bombers in the world (B-15 and B-19) and was certainly interested in how to shoot down an enemy bomber of similar size. But shooting down such large (but slow) bombers was a much different problem than shooting down fighters or twin engine aircraft.

The thread is about the uses of the big Browning pretty much as it stood or small changes. Major changes, for most countries, would come to late. Like a lot of things, timing was key. A better gun/ammo that shows up just a few months after contracts are signed and tooling ordered for a slightly lower performing gun may be rejected because of the delay in getting any guns it would cause by switching.

The Japanese tried to get around the fuse issue in their 12.7mm ammo by using a more sensitive explosive and/or using a small amount of trapped air and the heat of compression from impact to start the detonation process. A number of Ki 43s were fitted with very gauge sheet metal (or thin armor) troughs in front of the guns and over the engine because of the number of premature detonations as the rounds left the barrel.

Exploding 12.7-16mm bullets/shells may very well be more effective than non-exploding ones. But they are going to very much more expensive and not much cheaper than the more effective 20mm shells. The 20mm shells need more material but roughly the same amount (o r slightly more) of machining and assembly time.
There is no law of nature of physics that says that more countries could not have adopted the Browning or forms of it and what ever problems there there were could have been solved. The question becomes if they could have solved in a timely manor or not affected other things.
The British saw the Hispano in 1936 and finally decided on it in 1938, it took about two years to get it into service and it still needed modification/s. Between 1936 and 1938 they were getting the .303 Browning into production. Getting the Vickers K gun into production for the RAF ( and FAA). The Army was getting Bren guns, 7.92 Besas and 15mm Besas into production. Perhpas the last could have been ditched and the big Browning used instead? Navy was going for the Oerlikon (and the guns were not interchangeable in use even if the projectiles were, different maintenance requirements and such). Other countries were in the same boat, You did have salesmen from various countries/companies trying to flog their products around not only Europe but South America and Asia. Many times the "products" were not trouble free and the salesmen were looking for development funds as much as selling weapons as they would become known during WWII.

 

[kool kitty89]

The Japanese tried to get around the fuse issue in their 12.7mm ammo by using a more sensitive explosive and/or using a small amount of trapped air and the heat of compression from impact to start the detonation process. A number of Ki 43s were fitted with very gauge sheet metal (or thin armor) troughs in front of the guns and over the engine because of the number of premature detonations as the rounds left the barrel.

Wasn't that design an extension of the older PETN filled unfuzed exploding .303 british rounds? (I don't think they were much used by the british but more by Japan)

The British used self-detonating compositions in their incendiary shells though. Using hot burning low explosive (flash powder like) compositions seemed to be the effective compromise that both the Germans and British settled on for rifle caliber rounds, except the germans resorted to the relatively costly method of fuzing those incendiary rounds even in 7.92 mm, unlike the Mk.VI/VII .303. (or similar Vickers .50) And of course, 13 and 15 mm German incendiaries were fuzed as well. (though they seem simpler and certainly smaller and more compact than the British Mk.V )
The 7.92 mm B-patrone explosive incendiary 'spotter' round seems to have gotten away with a fairly simple impact fuze using a firing pin and tetryl charge.

Bad Request

That seemed to allow a very good ballistic shape as well, compared to most cannon shells and fuzed HMG shells. I'm not sure why such wasn't employed on larger designs. (perhaps impact sensitivity relative to the larger rounds, or more complex fuzing required -especially for detonating relatively insensitive high explosives -except tetryl should have been plenty useful as a primary detonator, so perhaps just the smaller mass and higher velocity of the 7.92 mm rounds making more reliably jarring impacts)

The British saw the Hispano in 1936 and finally decided on it in 1938, it took about two years to get it into service and it still needed modification/s. Between 1936 and 1938 they were getting the .303 Browning into production. Getting the Vickers K gun into production for the RAF ( and FAA). The Army was getting Bren guns, 7.92 Besas and 15mm Besas into production. Perhpas the last could have been ditched and the big Browning used instead? Navy was going for the Oerlikon (and the guns were not interchangeable in use even if the projectiles were, different maintenance requirements and such). Other countries were in the same boat, You did have salesmen from various countries/companies trying to flog their products around not only Europe but South America and Asia. Many times the "products" were not trouble free and the salesmen were looking for development funds as much as selling weapons as they would become known during WWII.

Given the british weren't particularly interested in synchronized guns, the oerlikon cannons (and maybe madsen) would seem more attractive with lesser development than the browning anyway. (the same would apply to several other European air forces)

The RAF DID trial the hurricane with some variety of Oerlikon gun but either the FFS or some derivative of the older, heavier Oerlikon S, and in any case they proved unsatisfactory for similar reasons to the early Hispano. (I'd thought it was the FFS, but looking again it could have been something else implying the FFS itself might have been more workable -the FFL should still have been less troublesome, the FFF more so but that wouldn't have near the AP capability the Air Ministry wanted ... though if it was the only weapon trialed that actually functioned reliably in the Hurricane, it may have merited a re-think)


For defensive mountings, the .50 vickers might have been more seriously considered along with potential replacements. (browning derived or otherwise -something like the Scotti gun wouldn't be too bad, the Browning derived Ho-103 was faster firing though given the Vickers K managed similar rate of fire to the M1919, scaling that up to .50 Vickers might have been particularly useful)

I believe the .50 Vickers aircraft gun was already 24 kg with similar 700 rpm to the Scotti, if more jam prone. (but again should be easier to deal with in turret/flexible mount, and preferably would be replaced with a better gun later on) The Japanese pushed their .303 vickers up to 900 RPM, so maybe there'd be some potential for improvement on the .50 as well, in the interim?

The only other advantage of the .50 vickers was its more satisfactory performance than the older M1 .50 cal browning and lack of licensing required for production. (that and being belt fed, but the .303 vickers had that advantage over the Lewis and Vickers K as well)