Would having the gas piston or impingement system below the barrel instead of on top help in reducing recoil?By pizza654
This is my first post and im no physicist so if this sounds stupid to you please explain to me why its dumb because I always like learning new things about gun design. Anyways ive had this idea in my head for a while now about a rifle concept and it first popped into my head when I was looking at the mechanics of a pkm. Like a lot of belt fed guns the piston is on the bottom of the barrel instead of the top and because the bolt and piston is so low it gives the pkm a good recoil impulse. My thought was how come no ones ever designed a rifle with the gas system below the barrel instead of on top? Imagine a SCAR but the barrel and the piston gas block is reversed.
This is one modern rifle that I'm insanely interested in, especially since there was a TFB article that hinted that there was a .308 Winchester/7.62mm NATO version being worked on that might use the same upper as the 5.56mm NATO version that HK has shown in several different versions since 2017.
This is the latest (known) iteration of the 433, and if you've seen some of the POTD posts at TFB since May of last year, you've probably seen it a time or two. In short, the 433 is HK's answer to the FN SCAR and to try and one up it. IMO, the most interesting thing about the 433 is that it seems capable of taking way more caliber rounds than items such as the FN SCAR or the Bren 2, which needed new uppers in order to go rounds like .308.
Out of curiosity one day, since I've seen numerous (though not often very new) photos of the 433 and I've also seen patent documents (I'll provide a link to patent documents and an article on Spartanat with some photos of the Gen 5 433), I decided to see if my own thoughts on the 433 being caliber convertible beyond .300 Blackout or 7.62x39mm held water. Using a simple image scaling and measuring program, I've determined that the 433 upper, as is, is capable of taking rounds or at least magazines of 71-72mm OAL. Mind you, this isn't exact, and I was conservative with my measurements.
Of course, this does further peak my curiosity on what the 433 is capable of firing and how caliber convertible it may be. On top of of course how it comes apart and various details about it.
Now the documentation. Spartanat is an Austrian site, and hence is in German, and being new here I'm not sure how Google translate works when linked, so I'll just leave the link (which has good, albeit sadly not ultra HQ/high res images, which IMO is a damn shame) to be copypasta'd into Google's translator or your favorite translator. On the plus side, there's a PDF in the article that you can save or convert to a pretty high res JPG or PNG image, and Google does a decent job of translating the PDF, too:
Now here's the patent documents and images. This series mostly pertains to the charging handle system, but it shows a good idea of how the guts of the 433 are laid out:
By That’s Suspicious
So after doing some sluething on my state laws, I discovered some pretty major loopholes in handgun ownership for those under 21 (I’m 19)
From what I’ve gathered and from what I’ve been told by those I know in law enforcement and those currently serving in the military, I can legally own a handgun and actually carry the handgun in my vehicle even though I’m not 21 due to some loopholes in handgun and firearm ownership laws.
What would be a good starter handgun to buy as my first handgun? I would like to buy one now and then get my CCW and use that handgun for when I’m legally allowed to carry it on my person. I personally wouldn’t mind carrying SOME full sized handguns like a Glock 17 or M&P 2.0
Also what would be a good starter AR to get that’s below $1,000; that’s another firearm on my list to soon get.
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.