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Found 4 results

  1. Bash the EM-2 Thread

    Here at Sturgeon's House, we do not shy from the wholesale slaughter of sacred cows. That is, of course, provided that they deserve to be slaughtered. The discipline of Military Science has, perhaps unavoidably, created a number of "paper tigers," weapons that are theoretically attractive, but really fail to work in reality. War is a dangerous sort of activity, so most of the discussion of it must, perforce, remain theoretical. Theory and reality will at some point inevitably diverge, and this creates some heartaches for some people. Terminal, in some cases, such as all those American bomber crews who could never complete a tour of duty over Fortress Europe because the pre-war planners had been completely convinced that the defensive armament of the bombers would be sufficient to see them through. In other cases though, the paper tiger is created post-facto, through the repetition of sloppy research without consulting the primary documents. One of the best examples of a paper tiger is the Tiger tank, a design which you would think was nearly invincible in combat from reading the modern hype of it, but in fact could be fairly easily seen off by 75mm armed Shermans, and occasionally killed by scout vehicles. Add to this chronic, never-solved reliability problems, outrageous production costs, and absurd maintenance demands (ten hours to change a single road wheel?), and you have a tank that really just wasn't very good. And so it is time to set the record straight on another historical design whose legend has outgrown its actual merit, the British EM-2: EM-2ology is a sadly under-developed field of study for gun nerds. There is no authoritative book on the history and design of this rifle. Yes, I am aware of the Collector's Grade book on the subject. I've actually read it and it isn't very good. It isn't very long, and it is quite poorly edited, among other sins devoting several pages to reproducing J.B.S. Haldane's essay On Being the Right Size in full. Why?!!?!! On top of that, there's quite a bit of misinformation that gets repeated as gospel. Hopefully, this thread can serve as a collection point for proper scholarship on this interesting, but bad design. Question One: Why do you say that the EM-2 was bad? Is it because you're an American, and you love trashing everything that comes out of Airstrip One? Why won't America love us? We gave you your language! PLEASE LOVE ME! I AM SO LONELY NOW THAT IT TOLD THE ENTIRE REST OF EUROPE TO FUCK OFF. Answer: I'm saying the EM-2 was a bad design because it was a bad design. Same as British tanks, really. You lot design decent airplanes, but please leave the tanks, rifles and dentistry to the global superpower across the pond that owns you body and soul. Oh, and leave cars to the Japanese. To be honest, Americans can't do those right either. No, I'm not going to launch into some stupid tirade about how all bullpup assault rifle designs are inherently a poor idea. I would agree with the statement that all such designs have so far been poorly executed, but frankly, very few assault rifles that aren't the AR-15 or AK are worth a damn, so that's hardly surprising. In fact, the length savings that a bullpup design provides are very attractive provided that the designer takes the ergonomic challenges into consideration (and this the EM-2 designers did, with some unique solutions). Actually, there were two problems with the EM-2, and neither had anything to do with being a bullpup. The first problem is that it didn't fucking work, and the second problem is that there was absolutely no way the EM-2 could have been mass-produced without completely re-thinking the design. See this test record for exhaustive documentation of the fact that the EM-2 did not work. Points of note: -In less than ten thousand rounds the headspace of two of the EM-2s increased by .009 and .012 inches. That is an order of magnitude larger than what is usually considered safe tolerances for headspace. -The EM-2 was less reliable than an M1 Garand. Note that, contrary to popular assertion, the EM-2 was not particularly reliable in dust. It was just less unreliable in dust than the other two designs, and that all three were less reliable than an M1 Garand. -The EM-2 was shockingly inaccurate with the ammunition provided and shot 14 MOA at 100 yards. Seriously, look it up, that's what the test says. There are clapped-out AKs buried for years in the Laotian jungle that shoot better than that. -The EM-2 had more parts breakages than any other rifle tested. -The EM-2 had more parts than any other rifle tested. -The fact that the EM-2 had a high bolt carrier velocity and problems with light primer strikes in full auto suggests it was suffering from bolt carrier bounce. As for the gun being completely un-suited to mass production, watch this video: Question Two: But the EM-2 could have been developed into a good weapon system if the meanie-head Yanks hadn't insisted on the 7.62x51mm cartridge, which was too large and powerful for the EM-2 to handle! Anyone who repeats this one is ignorant of how bolt thrust works, and has done zero research on the EM-2. In other words, anyone who says this is stupid and should feel bad for being stupid. The maximum force exerted on the bolt of a firearm is the peak pressure multiplied by the interior area of the cartridge case. You know, like you'd expect given the dimensional identities of force, area and pressure, if you were the sort of person who could do basic dimensional analysis, i.e. not a stupid one. Later version of the British 7mm cartridge had the same case head diameter as the 7.62x51mm NATO, so converting the design to fire the larger ammunition was not only possible but was actually done. In fact, most the EM-2s made were in 7.62x51mm. It was even possible to chamber the EM-2 in .30-06. I'm not going to say that this was because the basic action was strong enough to handle the 7x43mm, and therefore also strong enough to handle the 7.62x51mm NATO, because the headspace problems encountered in the 1950 test show that it really wasn't up to snuff with the weaker ammunition. But I think it's fair to say that the EM-2 was roughly equally as capable of bashing itself to pieces in 7mm, 7.62 NATO or .30-06 flavor. Question Three: You're being mean and intentionally provocative. Didn't you say that there were some good things about the design? I did imply that there were some good aspects of the design, but I was lying. Actually, there's only one good idea in the entire design. But it's a really good idea, and I'm actually surprised that nobody has copied it. If you look at the patent, you can see that the magazine catch is extremely complicated. However, per the US Army test report the magazine and magazine catch design were robust and reliable. What makes the EM-2 special is how the bolt behaves during a reload. Like many rifles, the EM-2 has a tab on the magazine follower that pushes up the bolt catch in the receiver. This locks the bolt open after the last shot, which helps to inform the soldier that the rifle is empty. This part is nothing special; AR-15s, SKSs, FALs and many other rifles do this. What is special is what happens when a fresh magazine is inserted. There is an additional lever in each magazine that is pushed by the magazine follower when the follower is in the top position of the magazine. This lever will trip the bolt catch of the rifle provided that the follower is not in the top position; i.e. if the magazine has any ammunition in it. This means that the reload drill for an EM-2 is to fire the rifle until it is empty and the bolt locks back, then pull out the empty magazine, and put in a fresh one. That's it; no fussing with the charging handle, no hitting a bolt release. When the first magazine runs empty the bolt gets locked open, and as soon as a loaded one is inserted the bolt closes itself again. This is a very good solution to the problem of fast reloads in a bullpup (or any other firearm). It's so clever that I'm actually surprised that nobody has copied it. Question Four: But what about the intermediate cartridge the EM-2 fired? Doesn't that represent a lost opportunity vis a vis the too powerful 7.62 NATO? Sort of, but not really. The 7mm ammunition the EM-2 fired went through several iterations, becoming increasingly powerful. The earliest versions of the 7mm ammunition had similar ballistics to Soviet 7.62x39mm, while the last versions were only a hair less powerful than 7.62x51mm NATO. As for the 7mm ammunition having some optimum balance between weight, recoil and trajectory, I'm skeptical. The bullets the 7mm cartridges used were not particularly aerodynamic, so while they enjoyed good sectional density and (in the earlier stages) moderate recoil, it's not like they were getting everything they could have out of the design. note the flat base In addition, the .280 ammunition was miserably inaccurate. Check the US rifle tests; the .280 chambered proto-FAL couldn't hit anything either.
  2. Most historical arms and armor were made of metal, leather and stone. This is the thread for historical weapons and armor made of weird shit. This is an example of armor made from the Gilbert islands made of thick, woven coconut fiber. The helmet is made from a pufferfish. I've seen a set similar to this in another museum. The woven fiber body armor looked like it would be reasonably effective. Coconut husk is pretty tough and the vest was very thick. I wasn't so sure about the helmet. The Gilbertese were also the foremost users of shark's tooth weapons, although other Polynesians used them as well: Several historical examples I've seen are these strange, branching designs: Polynesians were not the only ones to use teeth in their arms. The Mycenian Greeks made helmets out of boars teeth. One such helmet is described in the Iliad, and there are a few archeological discoveries of such: And finally, a club used by Inuits made from the penis-bone of a walrus:
  3. The Museum of Retrotechnology

    Too often technology is portrayed a steady, linear series of more or less inevitable improvements. This is an easier illusion to maintain if you don't know anything about the subject. In fact, the history of technology is littered with insane, unworkable garbage. Things that didn't work, barely worked, might-have-beens, things that would perhaps be worth revisiting, things fit only for ridicule, and some things that make no sense whatsoever: Yes! Terrify your enemies with your new gunspoon! Note the direction of the trigger and the direction of the muzzle. What the hell were these even for? Attaching solid fuel rockets to a bicycle! We totes verified this idea in Kerbal Space Program, it'll be fine. An external combustion motor that uses ether instead of steam! Nothing could possibly go wrong with this! A turbine powered by boiling mercury! There is definitely nothing at all that could go horribly wrong with this! Douglas Self's Museum of Retrotechnology Site has all of these wondrous devices and more. Feast your mind on the retardation of the engineers and inventors of yesteryear, and be amazed that anyone is left alive on this planet. "Steampunk" ain't got shit.
  4. AMX-30: A Second Look

    Since the AMX-30 is about to be added to World of Tanks, I thought now would be a good time to take a look at the design. Conventional wisdom would have that the AMX-30 is a sort of retarded little brother to the leo 1. The designs did originally stem from a joint Franco/German tank project, which, like most multinational programs, fell apart when the partners involved realized they couldn't both be in the driver's seat. Actually, the AMX-30 and Leo 1 differ significantly in design priorities. The first surprise from a more careful look at the AMX-30 is that the armor is actually pretty good for the period: (And before Olifant and Xlucine freak about the inefficiency of hull sponsons, here is a picture of a bare hull, which shows that the sponsons are only used to support the turret ring and do not extend the entire length of the hull) Compared to T-54/55: 100 mm @ 60 degrees is 200mm LOS, while 80mm at 68 degrees is 213mm LOS. Over most of the front of the glacis, the AMX-30 actually has slightly better protection than the T-55! The ratio of trigonometric to effective thickness against APDS/AP type threats is about 2 for both of these inclinations: So, for sub 40 tonne vehicles, both the AMX-30 and T-55 had respectable protection on the hull. Indeed, the weak points of both vehicles would be the turret, which had similar LOS thickness, but at less slope and therefore less effective protection against AP/APDS. The extreme slope angle of the hull would also stand a good chance of deflecting period HEAT ammunition, which often did not fuse properly against highly sloped plates. Compared to the Leo 1: We see that, frontally at least, the French tank is much better protected (they're both paper-thin on the sides). Add to this the fact that the AMX-30 had a healthy -8 degrees of gun depression, and it starts to look like a pretty competent design. One of the tricks the AMX-30's designers used to keep the tank efficient and compact was an unusual layout of the torsion bars: (Thanks to Walter_Sobchack for the image) In a typical tank with torsion bar suspension, the turret basket sits on top of the torsion bars and the torsion bar bushings. This creates a dead space underneath the turret basket. The height from floor of the turret to the ceiling must be tall enough for the loader to perform their job (ideally standing, but in some cases crouched), so the height lost to the torsion bars must be made up above the turret ring. This forces the roof of the turret higher, and so increases the total armored volume of the tank, which increases weight. In the AMX-30 the third road wheel swing arm is reversed into a leading, rather than trailing configuration. This leaves a nice big gap where the turret basket can live, which eliminates the wasted space. AMX-30 is, so far as I know, unique among production tanks in using this suspension design. There was at least one Soviet prototype, the Object 277, that used a similar arrangement. While the AMX-30's suspension was unusually compact for a torsion bar type suspension, it was utterly unremarkable in performance. With 278mm of combined bound and rebound, it was essentially comparable to the M60A1 with 292mm. While this was quite a bit better than the British centurion and chieftain, which had utterly primitive suspension that lacked even independently sprung road wheels, it was a far cry from the Leopard 1, which boasted 407mm of independent road wheel travel. Armament and fire control in the AMX-30 was quite modern; even progressive. Unlike the T-55 and hilariously awful and primitive British designs, the AMX-30 had an optical rangefinder. Because the rangefinder had a wide 2 meter base, and because the commander sat behind the gunner, the rangefinder was operated by the commander as a concession to maintaining an efficient ballistic shape for the turret. The commander's station featured a cupola with 10 direct-vision periscopes (or "windows" as they are sometimes called), a ten power binocular telescope, and a counter-rotating override feature. The gunner was given two observation periscopes in addition to the gunsight, and the loader had a generous three periscopes. The vision from the turret of the AMX-30 was, by tank standards, excellent. Primary armament was the OCC 105 F1. This gun was quite comparable to the Royal Ordnance L7 seen in most other Western tanks of the period, except that it had a slightly longer barrel, a compressed air bore evacuation system, and a slower rifling twist rate. The French are unique in their rejection of passive bore evacuators, preferring the older style of compressed-air based system. The German big cats also featured a compressed air bore evacuator, so there is the tantalizing possibility that the French systems are based on that. If this is true, it would be a germ of truth in the myth that the 75mm gun on the AMX-13 is based on the panther's armament. I have not seen conclusive evidence one way or another. The reduced rifling twist rate of the OCC 105 F1 was to facilitate the famously weird Gessner "Obus G" projectile. Obus G, as I am sure everyone reading this already knows, was a shaped charge warhead where the shaped charge rode inside an outer shell separated by a layer of ball bearings. This allowed the outer portion of the projectile to spin while the shaped charge would not spin, as spin degrades the effectiveness of shaped charges. This design combined the accuracy of a spin-stabilized projectile with the HEAT performance of a fin-stabilized projectile. Actually, Obus G was slightly more effective than the M456 HEAT round of the L7. The slow rifling twist of the OCC F1 precluded the use of APDS projectiles. Any APDS projectile long enough to be effective would have too great an aspect ratio to be stabilized by the loose twist of the cannon. However, in the long run this was an advantage, as the slow twist rate proved well-suited to APFSDS type rounds when these were introduced in the 1980s. In another unusual move, the secondary armament of the AMX-30 was a 12.7mm weapon rather than the usual 7.62mm. This, if the user so desired, could be increased to a 20mm autocannon. Not exactly "coaxial," the secondary armament could be elevated to 40 degrees (vs. 20 degrees for the main armament), to be used against helicopters and low-flying aircraft. Prior to upgrades late in its service life, the AMX-30 was let down by that most syndrome of armored fighting vehicles; a dodgy powertrain. Prior to the 1979 upgrade, the AMX-30 had a rather fragile transmission that required a skilled driver in order for the tank to remain mobile. Apart from this regrettable downside of not working, the AMX-30's powerpack was admirably compact and helped keep the overall size and weight of the tank low. Had it not been let down by an unreliable powertrain, the AMX-30 could have been a big success on the export market. More other Western tank designs of the period, the AMX-30 showed excellent design discipline in keeping the tank small and light. Despite the characterization of the armor protection as useful only against small-caliber threats, the AMX-30 boasted frontal protection that was better than the Leopard 1 and comparable to the T-55. Alas, for the majority of its career, the AMX-30 was yet another reminder that in the absence of a robust powertrain no amount of clever design features will redeem a tank. (Would be much obliged if someone would repost this to HAV after re-uploading whichever pictures need re-uploaded to imgur. I am too tired now and CBA)
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