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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)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.
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).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.
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)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.
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?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.
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.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?
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)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?
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 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.
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.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.
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)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.
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)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.
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.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.
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.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.
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 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.
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 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.