So, in the time between the suppressor design that I am doing for work, I decided to go after a semi clandestine manufactured SMG. The criteria driving the design is that round tube is incredibly common in SMG designs, so I wanted to avoid that and use rectangular tube and bar stock. This minimizes the operations that require a lathe, and while they ideally would be done on a mill, they can be accomplished with a drill press and hand tools if you have the patience. Some of these parts are innocuous enough that they could also be farmed out to local machine shops without raising eyebrows. Strangely, one of the larger issues that has faced clandestine small arms manufacturing is an acceptable human interface. Other people solve this by traditional methods such as carved wood grips, or cast/molded plastics, but that is a time consuming process to make a part that should be very simple. My solution was to use handlebar grips from a bicycle. They are already designed to provide a griping surface for your hands, and they are common enough and varied enough that you could will not have a problem sourcing them.
As far as the design goes, it is still a work in progress. The receiver is pretty much dialed in, as are the trunnions, the barrel, barrel retention system, etc. The FCG has been a sticking points, as designing them is probably my greatest weak point when it comes to arms design. As the FCG is horribly incomplete, the bolt may similarly undergo changes. It is currently planned to have a linear hammer, but that is still in the works. I have only begun to consider what to do for the stock, and the forearm will probably come last. The design uses Uzi magazines, and I'm toying with the idea of being able to change magazine compatibility by having alternate lower receivers.
There are two primary versions; the 9" barrel original design, and the 5" barrel design.
Charging handle/bolt/action spring interface
Early receiver, designed to be cut out of 1x2" 11ga rec steel tube. The notches near the trunnion and front barrel support are to allow the components to be welded together.
charging handle and barrel retention system details. The action spring guide rod runs through the front barrel support and in conjunction with the receiver it locks the barrel retainer plate in place. The retention plate slips into a grove cut into the barrel. This prevents the barrel from moving backwards out of the receiver, while the square section at the breech of the barrel nests in the trunnion to prevent forward movement. The barrel is not rigidly fixed to the receiver, but this is acceptable considering the intended applications of the weapon.
have question about 12.7x99 AP M2 cartridge WWII time books gives muzzle velocity for AP M2 - 895 m/s for 45in barrel, modern days firing tables and manuals gives 856 m/s for 45in barrel, which is correct, or both correct but 1st for WWII and 2nd for modern dayes cartridges ?
Hi everyone, first post here
I stumbled across this video :
It’s super dense polyethylene with a neutral buoyancy core for impact resistance. It weights only 4 pounds, so for weight effiency it’s around 3 times better than ar550 and 4 times better than other ceramics ballistic plates, AND that’s while including the water, which I doubt add any bulletproof capabilities.
Is it just me or does it sound a bit fishy?
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 I 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.