USAAF 0.60" Cannon

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Off the main topic, but on the .276 Pedersen and small arms:

Actually, the M1 Garand was part of a competition for both a new service rifle AND a new service rifle round.

The Army wanted an autoloader, and both Garand and John Pedersen (Remington's chief designer for years ) submitted rifles for consideration. They were originally both submitted in .276 caliber (designed by Pederson), and then also in .30 cal when the Army decided it wanted to stick to the .30-06 cartridge. The Garand rifle won the trials, and for good reason. Garand's was the better design. Pedersen developed a good cartridge, though. The Ordnance boards actually preferred the .276 Pederson round*, but were overruled, in part because the final decision was made in 1932 - the worst part of the Great Depression in the US, when the government was trying to cut as many costs/expenses as possible.

Aside from the "we've got lots of .30-06 ammo, and we don't want to complicate supply issues by having two different rounds at the platoon level", the .276 P. got a bad rap because Pederson goofed a little in making his prototype rifle - it required the cases of the .276 round to be wax-lubed externally in order to provide reliable extraction - while the same round in the Garand prototype did NOT require case lubing at all.
The waxed cases turned out to be quote robust and durable in their final form, though added cost may have been a concern as may have been the hot, melted wax being more likely to cause burns if handled soon after firing or (perhaps more importantly) collect dirt/debris after firing and require more work/cost to reload. (clean, strip, reload, then wax again) And reloading brass was a major concern for economic reasons, and one that long predated the depression. (I believe this was also why brass catchers were used on some fighter aircraft, including draggy external boxes used in training)

Pedersen didn't really goof in designing the rifle: it was a toggle-delayed blowback system and (as with most blowback and delayed blowback systems) had high pressure extraction issues. (German-derived roller-delay systemed had the same problems, but solved them with fluted chambers). Though I'm not quite sure why he used the cartridge dimensions he did, as the heavy taper made for a larger case head/base than otherwise would be needed, which increases bolt thrust and thus requires more delay force (or a heavier bolt) for a blowback system. This is also why .30-06 made a poor choice for any blowback derivative, the significant bottleneck increases bolt-thrust a great deal. (one of the many reasons contributing to the very troubled Thompson Auto Rifle ... and also why Winchester's self-loading cartridges of the 1905, 1907, and 1910 as well as Oerlikon style API-blowback weapons all tended to use straight-walled cases; the .30 Carbine case is relatively well suited to blowback for the same reason, though not for the 5 pound limit the Army wanted on the M1 Carbine ... had it been 7 pounds, a simpler 1905/1907 style straight-blowback mechanism would've worked). I'm not sure why Pedersen didn't just start with something more like the .30 Remington, perhaps with a slightly longer case for more powder (or just operating at higher pressures than the .30 Rem was rated for). He could have gone down to the smaller 7mm bullet too, but .30 cal would've likely worked fine in the slimmer case. (7mm has recoil advantages for the shooter, and the ballistics he worked out as it was were quite good ... but using the .30 or .25 Remington case would've reduced bolt-thrust by about 14% compared to the .276 cartridge he developed, plus the straight-walls would make for simpler, somewhat more compact, square/straight box magazines or en bloc clips)

As it was, the cases were still slimmer than .30-06 and allowed for 10 round capacity clips rather than the reduced 8 rounds of .30-06 later on.


* The .276P, despite having a lighter bullet, actually had better long-range ballistics than the .30-06 - its flight path was flatter to between 800 and 900 yards, and had higher retained energy between 400 and 800 yards (past 800 yds the .30-06 does better, but that was mainly useful for snipers, not common infantry). Additionally, with a ~1/2" shorter case of smaller diameter than the .30-06, and the ability to hold 10 rounds in the Garand (vs the 8 allowed by the .30-06), more rounds of ammo could be carried for the same weight and volume in the can and in the Garand's magazine.

for those who think that the .280 british and the .276 pedersen were pipsqueak cartridges, in comparison to the .30-06 or the .303 british ...
Following various reports cited on Forgotten Weapons, I think the long range ballistics were inferior to .30-06 but basically equal past medium range and superior to the old M1906 ball load while slightly higher velocity and flatter shooting at close range than M1 ball. (comparing 125 grain .276 at around 2,800 fps with 174 grain M1 Ball at just over 2,600 fps) M1 ball was similar to match-grade .30-06, longer, heavier, and boat-tailed. (also somewhat higher recoiling than the older 150 grain load and moreso compared to .276 pedersen, so follow-up shots could be more rapid with the latter and, potentially, full automatic fire more controllable as well had it been made in a LMG or automatic-rifle)

However, the ultimate irony was that shortly after MacArthur got his way with .30-06 standardization for infantry rifles and machine guns, it was discovered that M1 ball had excessive long-range performance and was penetrating backstops at a number of training facilities, posing safety issues and was subsequently restricted along with an emergency order to substitute a load similar to the older 1906 type, resulting in M2 ball, which in any event still had slightly higher weight (152 grains) and higher velocity (around 2,800 fps rather than 2,700) than the 1906 loading, but was satisfactory for the long-range concerns due to the poorer ballistic coefficient of the flat-based projectile. (later on the 165 grain, flat-based but slightly longer M2 black-tip AP round became a popular benchmark, and it was that that the .280 British would end up faring poorly against ... ironically the latter had broadly similar characteristics to .276 Pedersen, though the British shifted towards higher bullet weights to try and satisfy long-range performance the US insisted on; I'm not sure why a boat-tailed load wasn't implemented or some other shape changes that should've further improved the .280's BC more like Pedersen had done back in the late 20s, albeit with generally lighter bullets)

So the economic/cost argument for having to manufacture all-new ammo was killed in 1936 when the rush to switch over to M2 ball was made. (though the stocks of existing M1 ball were presumably used in machine guns, probably aircraft or AA mounts in particular, but not standard infantry use ... some may have also had use with snipers, but I haven't seen any official application of such: it was a more accurate, longer range loading and if available, should have been popular with sharpshooters/snipers) So the only advantage remaining was logistics, which was both marginal and questionable considering the lower weight and size of .276 pedersen (advantages in transport/storage logistics) and the use of 10 round rather than 8 round clips. On top of that was manufacturing logistics, as the .30-06 Garand both took more time to refine for production and was more costly and risky, particularly with initial difficulties engineering and manufacturing the right-angle bend/step of the operating rod where the .276 version had a simpler-to-manufacture straight op-rod. (volume production likely would've started earlier, initial costs would be lower, and the shortages/delays that led to the USMC being limited to bolt-action M1903 rifles early-war may not have existed at all) On top of all that, with the .276 they had the Pedersen rifle design as a fallback if something unforseen happened to the Garand design, plus the British were interested and Vickers had supplied preproduction examples as well as planned for potential mass production from foreign buyers, and it was possibly the British would have adopted the Pedersen rifle (at least to some limited extent) had the US formally adopted the .276 cartridge. (they were looking to move away from the .303 British cartridge and had been doing so since before WWI, and considered switching to .30-06 or 8mm Mauser at various points during WWII as well, plus their post-war .280 cartridge ended up sharing many qualities with the .276 Pedersen)


Also oddly enough, the Germans had stuck with their lower-BC flat-based WWI vintage 152.7 grain S. Patrone 8x57mm loading right up to rearmament under the Nazi regime when it was found that the lighter bullet and heavier powder load gave excessive muzzle flash in the shorter-barreled Kar 98k rifles, and instead of changing the powder formulation, downloading (potentially with a lighter bullet, but longer/boat-tailed bullet for similar or superior ballistics) they standardized on the much heavier and somewhat more expensive 198 grain boat-tailed S.s. Patrone with lower velocity (760 vs 878 m/s), much better BC and significantly more recoil. (also note the older load had a higher, 890 m/s velocity out of the longer-barreled G.98 rifles) Albeit the change in ballistics was a good deal more severe than .30-06 had been, as sectional density and BC of the earlier 152.7 grain ball load had been a good deal poorer. (also the heavier recoil and heavier bullet/cartridge weight and transport/supply/burden were incentives for the 8x33 Kurz cartridge to be developed ... had the standard 8x57 ball been shifted to a lighter, lower recoiling load, there might have been less contention there and less infighting with Hitler over his disdain for the Kurz cartridge, albeit the Italians were in an even better position with their 7.35 mm Carcano and it's modest ballistics, though I'm not totally sure why they hadn't just adopted a light-ball, BT-spitzer variant of the existing 6.5mm cartridge, or switched to the far more common 7mm bore, which also probably would've allowed re-boring older 6.5 mm barrels without excessive loss of structural integrity, as would 6.8 mm or .270 caliber in US metrics, less common but still a known caliber with existing tooling/production built around that bore and bullet diameter; the 6.5 Carcano was also not the common near-6.68mm diameter bullet of most other 6.5 mm cartridges, but rather was 6.80mm, so did pose some issues there, and that's also why the Carcano rifles got a port reputation post-war, due to undersize bullets and poor consistency: plus the properly-sized Italian surplus ammo was somewhat mediocre in itself; otherwise commercial loadings nearly identical to 6.5x54mm MS should have existed)
 
we are drifting way off topic.

I would note however that as good as some of these cartridges might have been for rifles they may have left something to be desired for machine guns. Between the wars (.276 Pedersen) the standard round had actually been changed to the .30-06 M1 ball with a 174 grain bullet (9 degree boattail) at about 2600fps. this gave several thousand extra yards of range to the tripod mounted 1917 Browning water cooled machine guns used for battalion fire support. However this round was just a little too stout for the M1 rifle and in the interest of reducing the wear and tear on the rifles the M2 ball was adopted (duplicating the external ballistics of the 1906 round but at about 42,000cup rather than 50,000 cup )

In emergencies the machine guns could fire the rifle ammo and vice versa. If your rifes are using .276 and your machine guns are using .30-06 that doesn't work.

You also have trouble tying to make small caliber tracer ammunition.

How important some of these things are I don't really know but they are considerations that factored into the decisions of the time (to a greater or lesser extent)
 
This can't be the only factor in play as the US Army was quite interested in both the 20 and 23 mm Madsen cannons, but apparently mostly rejected them on the basis of cost/complexity of machining the curved components it used
That's a good point! It is weird that they'd pursue the Madsen but not the HS.404.
Additionally you had the adoption of the Hispano HS.404 based on French specs, but that had continuous reliability and some quality control problems. (the NIH issues may have contributed to that, ignoring British advice on improving it, though apparently tolerances were also too loose due to being relegated to the Artillery category
I assume the USN didn't have this restriction?
Presumably the 37 mm M4/T9 was conservative and foolproof enough to work well with those tolerances and was based on a weapon already in use as ground Artillery.
I was curious why the 37mm didn't have issues despite the tolerances.
The Army was also very interested in a high velocity 23 mm cannon and did some development work on that pre-war and early war, but didn't find anything satisfactory
Why didn't they use short recoil?
 
Some of it might be timing. The Hispano wasn't a production gun until 1938/39. It had been demonstrated several years earlier but it wasn't really ready to go. Hispano also wanted some pretty steep licencing fees.
Without knowing the details of the Madison licencing plan it is hard to judge.
A drawback to the Madison was the low rate of fire compared to the a Hispano.

The low rate of fire 37mm may have been more tolerant of loose tolerances than the faster firing cannon? The long recoil system has more time for things to happen and more weight/force to keep things going.
The Hispano fired faster than the Oerlikon, in part by using a lighter breech block but that means less momentum to overcome rough spots or less than ideal ammo.
 
The Army may have had a valid theory with their high velocity guns. Execution was a problem. The development of the gyro gunsight achieved a lot of the goals of the high velocity guns
I'm surprised if the gyro sight corrected things, that they kept on going with the 0.60" gun. Was this an example of bureaucratic inertia?
It could take 4-6 years (and longer) to bring a gun from initial concept to a finished, reliable service weapon. The contract that lead to the M-61 Vulcan gun was issued in 1946, first guns weren't test fired until 1949, and first real service use wasn't until 1959.
I thought it was 1958...

BTW: Though something that I didn't think about until I was, of all things, standing in the shower yesterday (don't ask me why some things pop into my head at the time they do -- I haven't figured it out yet): The RAF was fine with 20mm cannon at the end of WWII, and they were quite aware of the advanced technology on the horizon. Why were they fine with the 20mm and not the USAAF?
 
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The RAF was fine with 20mm cannon at the end of WWII, and they were quite aware of the advanced technology on the horizon. Why were they fine with the 20mm and not the USAAF?
IIRC reading, the 20MM on this side of the pond tended to have reliability issues, ostensibly because our ordnance people tried to "improve" some of the design details IAW certain "theories" that they were unwilling to accept were faulty. Did I get that right, Shortround?
 
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It kind of reminds me of the expression "if it ain't broke, don't fix it". Some people don't believe in that shit, instead subscribing to "if it ain't broke -- fix it 'till it is!":D
 

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