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Designing A Rifle From Scratch(ish)


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BCG:     10.5" lightweight barreled version     "SCAR-alike" config for weight comparison:             Final weights (no

There were a few things I wanted to do with this rifle. First and foremost, I wanted a roughly "AR-like" rifle that incorporated all or most of the reliability elements I had identified in the AK seri

It's worth noting that many manufacturers, even some well regarded, choose to include M-Lok only on those surfaces and angles they deem most useful, using other (presumably cheaper or stronger) cutout

The rifle now has a magazine (body, at least):

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AxoSjHT.png

 

Turned lines on to highlight some of the details. The magazine is based on a combination of AK, and vz. 58 magazines, and the Gen 3 PMag. Many of the dimensions were taken from the AK-74 magazine which combined with some features from the PMag caused some issues. Protip: Thick feed lip walls are a pain in the ass. However, I was able to work around them without too much difficulty. IIRC, @Ulric you ran into this same issue when designing one of your magazines, thick AK feed lips mean the magazine has to be lower which means the ammo presents lower. Not a huge problem, necessarily, but one worth noting.


Right now, the magazine is supposed to be straight insert, like an AR-15 magazine, but index on a horizontal surface (that big ridge running along the outside of the mag body) like an AK or vz. 58. The rear wall of the magazine is straight and continues a little past the ridge because it will accommodate the magazine catch. 

 

One of my goals was to make the feed tower as short as possible. Currently, it is approximately the same height as an AK. I would like to make it even shorter than that. The reason is that the shorter your feed tower is, the more workable drum magazines become (as they don't need large feed towers, dummy rounds, etc - or at least as many). The limitation on this currently appears to be how thick my polymer lower needs to be for structural integrity. Once I start working on the lower, I may find I can reduce the height of the feed tower even more, which would be nice.

 

Like both an AK-74 mag and a PMag, there are "driving" features in my magazine which point the rounds towards the center of the bore during feeding. This is a particularly good thing in my design as my rounds need to make it in the negative space between two lugs on the barrel extension. But if I can achieve this, then it should give me a very nice, clear feedway. 

 

But, so far so good.

 

 

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Just now, Xoon said:

Out of curiosity, what is your target group for this rifle?
Military, sport, hunting, fun and/or you?

 

It's a project for my portfolio and to improve my SolidWorks skills and also to stave off my sense of personal dread.

 

The rifle itself is designed as if it were intended for the military.

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4 minutes ago, Sturgeon said:

 

It's a project for my portfolio and to improve my SolidWorks skills and also to stave off my sense of personal dread.

 

The rifle itself is designed as if it were intended for the military.

That's nice. 
Are you going for a light rifle, sturdy or is it still up in the air? 
Just to give a example of two rifles that fall in each category:
AG-3, Norwegian produced modified G-3, very rugged rifle which can take a beating and be abused a lot, often joked about being used as a hammer. 
HK-416, new service rifle and very light and ergonomic, though has a few complaints from soldiers transitioning from the AG-3 about it being too flimsy and easy to break.

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42 minutes ago, Xoon said:

Are you going for a light rifle, sturdy or is it still up in the air? 

 

"Yes"

 

I wouldn't put rifles into those sorts of categories, nor neither of those rifles into those categories necessarily. The design processes of making a rifle work reliably making it lightweight aren't exclusive to one another, nor is there a single-dimension metric of either reliability or light weight. A G3 may be a reliable rifle with the right ammo - or it may not be. They tend to have higher parts breakages rates than other guns because their action is fairly violent. They are also, for their caliber, one of the lighter guns of the era (especially when you account for the aluminum magazine). On a similar line, the M16A2 is one of the lightest rifles designed in the 1980s, but good luck breaking one! Likewise, there are guns that are quite heavy and also surprisingly fragile, such as the Stoner 63 or L85A1.

 

Having said all that, I am happy to write a bit about what I'm going for here. Post to follow.

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16 minutes ago, Sturgeon said:

 

"Yes"

 

I wouldn't put rifles into those sorts of categories, nor neither of those rifles into those categories necessarily. The design processes of making a rifle work reliably making it lightweight aren't exclusive to one another, nor is there a single-dimension metric of either reliability or light weight. A G3 may be a reliable rifle with the right ammo - or it may not be. They tend to have higher parts breakages rates than other guns because their action is fairly violent. They are also, for their caliber, one of the lighter guns of the era (especially when you account for the aluminum magazine). On a similar line, the M16A2 is one of the lightest rifles designed in the 1980s, but good luck breaking one! Likewise, there are guns that are quite heavy and also surprisingly fragile, such as the Stoner 63 or L85A1.

 

Having said all that, I am happy to write a bit about what I'm going for here. Post to follow.

You have a point, but I think I was a bit unclear. I meant making the rifle more abuse proof that normal, not sincerely more reliable. 
For example stronger charging handle, as the HK416s is easy to break with too much force, thicker frame which does not bend or get dented that easily. Soldiers do the weirdest things with their rifle, including using them as chairs, hammers and spears. 

I appreciate you taking the time to answer my questions by the way.

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Just now, Xoon said:

You have a point, but I think I was a bit unclear. I meant making the rifle more abuse proof that normal, not sincerely more reliable. 
For example stronger charging handle, as the HK416s is easy to break with too much force, thicker frame which does not bend or get dented that easily. Soldiers do the weirdest things with their rifle, including using them as chairs, hammers and spears. 

I appreciate you taking the time to answer my questions by the way.

 

I was sort of lumping reliability and durability together. The AR-15 charging handle has always been a bit of a kludge, but charging handles are a very difficult human engineering problem so it's stuck around (it has many advantages). It's not terribly surprising to me that an army transitioning from the G3, which takes a herculean amount of effort to charge, to an AR derivative would see some charging handle breakages. At the same time, the USMC (perhaps most notorious for being filled with people who can break and/or lose ball bearings given enough free time) has not really had a serious issue with charging handle breakages in the M16/M4 platform in the last 50 years. So I assume that's more an issue of adjustment than anything else. Those charging handles do break, though. One of the easiest field remedies for this is to just carry spares. They are cheap and light and easy to replace in the field, so it's not a huge issue.

 

No weapon can be truly "soldier proof". AKs are not, G3s are not, FALs are not, M1 Garands are not. Even Mausers can and do break. Of course it's important not to equivocate: Some rifles are not properly engineered for durability and are not appropriate for use by soldiers at all. I would definitely say the AR-18 is an example of such a rifle. They are extremely fragile in a number of important ways, and it's obvious why they didn't catch on militarily (though the AR-18 bolt group was copied by a number of lazy designers). The early M16 was also too fragile. There could be a very interesting discussion of what "underbuilt" really means with regards to rifles that would almost exclusively cover AR-15 variants. They run the gamut. The first 17 AR-15s were so light and fragile that a whole host of changes were proposed during testing in the 1950s which caused them to gain three quarters of a pound by the time they hit production as the Colt 601. Being underbuilt by that much is perhaps one of the most extreme and clear examples I can find. The 601, though, was still too light and by the time development of the M16A1 was done it would weigh 0.69lbs more than that, almost a pound and a half heavier than the first 17 prototypes when they came out of Armalite's shop. Not all of that weight was to improve durability or reliability, but almost all of it was. And even then, the 1970s era M16A1 still had shortcomings in durability, which led to the M16A2 growing by another half-pound. So the total difference between the M16A2 (which was fully ruggedized) and the first 17 AR-15s was nearly two pounds - that's more than even the weight growth of the Dutch AR-10, which grew by about 1 2/3s pounds over its development! The AR-15 is a smaller caliber rifle, too to so when we compare these in terms of percents the degree to which the initial AR-15 was underbuilt becomes very clear:

Dutch AR-10: Grew by 1.66 lbs (23% of initial weight)

 

AR-15: Grew by 1.92 lbs (34% of initial weight) (!!!)

 

So while a weapon cannot be soldier proof, nor is weight necessarily an indicator of ruggedness, it's also clear that it's very bad to under-engineer a weapon to such a degree as the original AR-15. If you do, then the next decades will be spent fixing your shit.

 

 

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1 minute ago, Toimisto said:

BTW, in which way is the AR-18 too fragile? and how would those be corrected.

 

Handguard, front hinge point, stock, fire control elements. The way to correct them would be to beef up all of those elements, but tbh it would be better to just redesign the rifle from scratch. Which is what most did.

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There were a few things I wanted to do with this rifle. First and foremost, I wanted a roughly "AR-like" rifle that incorporated all or most of the reliability elements I had identified in the AK series: Friction reducing anti-rotation devices, long bolt overtravel, a large degree of underslide, and a clear ammunition feedway, to name some of them. At the same time, I wanted my execution of those features to be different than the AK, as "stuff an AK up the ass of an AR" has been done about thirty fucking times by this point. I also deliberately eschewed some of the design characteristics of the AR-15, such as the tube-shaped receiver and cylindrical bolt carrier, because I did not want the end product to be basically just a "redux" of the AR, either.

 

Another feature I wanted to include was an extruded upper receiver because I had some ideas about how to do it while making it lighter, cheaper, and more adaptable. Also, three years ago I designed an optimized bolt lug contour, which I modified slightly and used as the basis for my bolt configuration. This contour was designed to maximize lug contact area, minimize lug rotation angle, and clear the rifle's feedway. You can see images of the study I did in 2015 below:

 

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The lug configuration I ended up using was the one in the second row of the last image, far right.

 

I knew at the beginning that I wanted the rifle to be in 5.56mm by default. I also wanted it to be expandable to other calibers, so the diameters and lengths of the bolt, barrel extension, and other elements are hybridized between the AR-15, AR-10, and SCAR. It should be able to take conversion kits for rounds as big as .308 without any issues.

 

I deliberately chose not to use USGI magazines for the rifle, for several reasons. Chiefly, the magazine is one of the most significant elements of the rifle and I wanted to design it myself. Second, AR mags are crap and designing your rifle around them is like designing a Formula-1 car to run on 87 octane. Third, the AR magazine well interior (which is necessary to make AR mags work) would not have allowed me to design a highly reliable and efficient drum magazine, which is something I am interested in.

 

For the gas system, I chose to use a gas-tube-to-tappet arrangement because of the chosen bolt carrier configuration and to prevent gas from being blown into the receiver. Not that this is a major limitation of the AR series, but... Why not?

Beyond all that, I designed everything to be both lightweight and durable, which means being very conscious of volume economy. Bigger guns are heavier and more fragile. Smaller guns are lighter and more robust. Because that's how mass works. So being small (within the parameters I set for myself) was important to me.

 

 

 

 

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4 hours ago, Sturgeon said:

 

I was sort of lumping reliability and durability together. The AR-15 charging handle has always been a bit of a kludge, but charging handles are a very difficult human engineering problem so it's stuck around (it has many advantages). It's not terribly surprising to me that an army transitioning from the G3, which takes a herculean amount of effort to charge, to an AR derivative would see some charging handle breakages. At the same time, the USMC (perhaps most notorious for being filled with people who can break and/or lose ball bearings given enough free time) has not really had a serious issue with charging handle breakages in the M16/M4 platform in the last 50 years. So I assume that's more an issue of adjustment than anything else. Those charging handles do break, though. One of the easiest field remedies for this is to just carry spares. They are cheap and light and easy to replace in the field, so it's not a huge issue.

 

No weapon can be truly "soldier proof". AKs are not, G3s are not, FALs are not, M1 Garands are not. Even Mausers can and do break. Of course it's important not to equivocate: Some rifles are not properly engineered for durability and are not appropriate for use by soldiers at all. I would definitely say the AR-18 is an example of such a rifle. They are extremely fragile in a number of important ways, and it's obvious why they didn't catch on militarily (though the AR-18 bolt group was copied by a number of lazy designers). The early M16 was also too fragile. There could be a very interesting discussion of what "underbuilt" really means with regards to rifles that would almost exclusively cover AR-15 variants. They run the gamut. The first 17 AR-15s were so light and fragile that a whole host of changes were proposed during testing in the 1950s which caused them to gain three quarters of a pound by the time they hit production as the Colt 601. Being underbuilt by that much is perhaps one of the most extreme and clear examples I can find. The 601, though, was still too light and by the time development of the M16A1 was done it would weigh 0.69lbs more than that, almost a pound and a half heavier than the first 17 prototypes when they came out of Armalite's shop. Not all of that weight was to improve durability or reliability, but almost all of it was. And even then, the 1970s era M16A1 still had shortcomings in durability, which led to the M16A2 growing by another half-pound. So the total difference between the M16A2 (which was fully ruggedized) and the first 17 AR-15s was nearly two pounds - that's more than even the weight growth of the Dutch AR-10, which grew by about 1 2/3s pounds over its development! The AR-15 is a smaller caliber rifle, too to so when we compare these in terms of percents the degree to which the initial AR-15 was underbuilt becomes very clear:

Dutch AR-10: Grew by 1.66 lbs (23% of initial weight)

 

AR-15: Grew by 1.92 lbs (34% of initial weight) (!!!)

 

So while a weapon cannot be soldier proof, nor is weight necessarily an indicator of ruggedness, it's also clear that it's very bad to under-engineer a weapon to such a degree as the original AR-15. If you do, then the next decades will be spent fixing your shit.

I see, you have taken a lot into consideration. 

One thing I think you should keep in mind later, is to make the rifle winter/arctic friendly, bigger trigger guard or the ability to flip it away or remove it. 
Any cast part can be skeletonized for weight savings i think too. No styling, basically, not this:

latest?cb=20100307170239

 

Oh and, If you want some advice on making parts more automation/mass production friendly, just ask. 

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5 hours ago, Sturgeon said:

 

Handguard, front hinge point, stock, fire control elements. The way to correct them would be to beef up all of those elements, but tbh it would be better to just redesign the rifle from scratch. Which is what most did.

Auto sear/Sear trip, especially so.

Saw more than a few with the "H" piece at the rear of the receiver , knocked loose.

 

And "E clips, Everywhere".

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1 hour ago, Xoon said:

I see, you have taken a lot into consideration. 

One thing I think you should keep in mind later, is to make the rifle winter/arctic friendly, bigger trigger guard or the ability to flip it away or remove it. 
Any cast part can be skeletonized for weight savings i think too. No styling, basically, not this:

latest?cb=20100307170239

 

Oh and, If you want some advice on making parts more automation/mass production friendly, just ask. 

 

Concur, I am not a fan of stylization on a rifle. Aesthetics should be incorporated where they don't interfere with anything else perhaps, but the "Audi treatment" is haram.

 

The AK is a good example of the correct application of aesthetics in a rifle, actually.

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6 hours ago, Toimisto said:

BTW, in which way is the AR-18 too fragile? and how would those be corrected.

 

On the AR-180B reproductions made by Armalite, the lower receiver hinge point is quite weak.  On the originals it's fairly beefy though.  Biggest complaint on the originals is the folding stock mechanism; that thing is just a pile of crap.

 

In general though, the AR-18 was cheap and not very good.  There were several good ideas that a lot of people lifted, like the broad design of the bolt carrier, but you'll note that very few countries elected to make complete clones.

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2 hours ago, Sturgeon said:

 

I've actually never seen one in person, let alone 3 actual -18s in the same collection.

 

 

That's what I figured.

 

The hinge hole consists not only of the end plate that's welded on to the front of the magwell, but also of an extension of the receiver itself.  The hinge hole is twice as thick as any other point on the rifle's receiver.  If the hinge point is a specific weakpoint, then you might as well throw up your hands and say that the entire damn rifle is flimsy.

 

But I would expect the stock hinge, last round hold open, handguard, or the really dodgy welds at the back of the upper receiver to go first.

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3 hours ago, Collimatrix said:

 

 

That's what I figured.

 

The hinge hole consists not only of the end plate that's welded on to the front of the magwell, but also of an extension of the receiver itself.  The hinge hole is twice as thick as any other point on the rifle's receiver.  If the hinge point is a specific weakpoint, then you might as well throw up your hands and say that the entire damn rifle is flimsy.

 

But I would expect the stock hinge, last round hold open, handguard, or the really dodgy welds at the back of the upper receiver to go first.

Quality issues with the welds? 

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      While many concepts were explored, the one that gained the most traction was for a generously roomy welded chassis, with standardized turret ring dimensions, so that turrets and hulls could be exchanged at the depot level. Running contrary to current Army thinking, which emphasized small hulls with advanced, efficient transmission layouts, the concept had a large hull rear, supporting space inefficient, but widely available automotive components.
       
      As the AVT refined the design, they worked closely with British and American automotive engineers to try and create a design that could easily be adapted for the different automotive components then available, and projected. The design was intended from the outset to contain at least the British Meteor engine, and the Merrit-Brown Z.51.R transmission used in the Centurion. Because of this, the tank could not be made very much smaller than the Centurion, but this was deemed acceptable.
       
      The hull design received the most attention initially, and design of the turret and armament initially languished. The AVT had to solve, satisfactorily, the problem of producing specialized fighting vehicle components - the gun, turret, and sighting systems - in a variety of nations. Eventually, it was decided that the facilities in more developed countries, such as the US, Britain, France, and Germany, that could produce armed turrets and rings for all users, to be shipped abroad and mated to locally produced hulls.
       
      One further problem facing the AVT was ensuring the transportability of the new tanks by the various trucks, ships, and railcars that were in use at the time by member nations. The solution was to limit the weight of the new tank to 40 tonnes, enabling it to be transported by the majority of surplus wartime infrastructure.
       
      The resulting hull design was highly convergent with, but distinct from the British Centurion tank. The armor plates were to be rolled, heat-treated, and cut to shape by industrially capable member nations with the industrial capacity, and then shipped along with automatic welding equipment, if needed, to member nations for assembly. Each welded part assembled together using dovetails - like a cardboard model - to improve the strength of the welds, allowing for somewhat expedited welding practices. The turret ring race and other senstitive contact areas were finished before the plates shipped. When assembled, the hull used a series of mounting rails for engine and transmission, which approximated very nearly the modern "powerpack" concept, albeit in a much less space-efficient form. The driver's position was accommodating, with appreciable space as well as adjustable controls and seating, and power-assisted steering levers and shifter.
       
      Armor on the hull consisted of a two three-inch plates joined at a 60 and 45 degree from the normal, attached to side plates two inches thick set at an angle of twelve degrees, like the Centurion. Top and bottom armor plates were one inch thick, while the rear armor plate was 1.5" thick. Like the Centurion, there was provision for .25" thick standoff plates mounted to the side of the hull, encasing the suspension.
       
      The hull was to be furnished with automotive components in-situ, so there was no standard engine or transmission. However, most studies were done with either the British Meteor engine and Merrit-Brown Z.51.R transmission of the Centurion, or the AV-1790 engine with CD-850 transmission of the T40 experimental US medium tank. Special mention, however, should be made of the design study of the tank using a Ford GAA engine and syncromesh transmission from an M4A3 Medium, intended as a backup configuration in the event that a member nation could not obtain more modern engines and transmissions. In this configuration, the mobility of the tank would be significantly decreased.
       
      Suspension was provided via a series of mounting points to which suspension elements could be attached. The "default" suspension configuration was for an individually sprung Horstmann derivative, but the design accomodated both single and bogied forms, as well as internal and external torsion bar, Bellevile washer, and volute spring methods of suspension. Track pitch, width, and design were likewise left up to member nations, but most early scale models used standard US 6" pitch 24" wide T81 tracks.
       
      Ancillary components, such as stowage boxes, lights, fuel tanks, and other minor details, were to be produced by the receiving nations, with stamping equipment and technical know-how distributed as needed. 
       
      With all of the allowed variation, AVT realized it would need to publish an "engineering guide" to the new tank design, by early 1950 somewhat uncreatively christened the "NATO Medium Tank". This was accomplished with the first trials of automotive pilots, and "AN ENGINEERING GUIDE TO THE NATO MEDIUM TANK" was published by ORO on July 21st, 1950, and distributed to member nations. As the document only detailed the dimensional and production aspects of the tank, it was not considered a security risk, as member nations couldn't possibly leak any sensitive information from it that they did not already possess.
       
      By 1950, the first mild steel turret mockups had been created, giving two of the automotive pilots a "proper" look, even though they were no more combat capable than before. The turrets were cast in a single piece, and fitted with a 90mm high-and-low velocity gun based on the British 20 pdr but utilizing experience gained from the American 90mm series of cannons. It was determined that for member nations, the most common type of shot available would be solid APC shot. Because of this, a high velocity conventional AP round would be needed to deal with anticipated Soviet vehicles. The resulting round fired essentially the same T33 AP shot as the 90mm M3 gun, but at a much higher velocity of 3,200 ft/s. Testing revealed the round could penetrate a 100mm RHA plate at 60 degrees from normal 80% of the time at 500m. This was considered, initially, sufficient to defeat the anticipated armor of Soviet medium and heavy tanks.
      In order to allow more fragile, and thus higher capacity HE and utility (smoke) shells, ammunition was also developed for the gun that used a foam-lined, reduced volume case loaded with a smaller charge. This high explosive round produced 2,100 feet per second with its unique 22 pound shell, loaded with 2.6 pounds of Composition B high explosive. The technical data packages for these two types of ammunition were widely disseminated to member states, for their local production.
       
      The new 90mm gun was also compatible with any projectiles for the older M3 series of cannons, including HEAT and HVAP. Further, it was expected that the cannon would serve as the basis for a new 100-120mm gun, designed to fire a new generation of HEAT and APFSDS projectiles.
       
      Also included with the armament were three unity periscopes for each crewman, a single-plane stabilization system for the main gun, and a gunner/commander cowitnessing system. The turret had two ready racks of five rounds a piece, with additional ammunition stowage planned to be in the floor of the vehicle, and adjacent to the driver.
       
      The turret was cast with 3.5-3.6" all around armor, improving to six inches at the front. A large, wide mantlet/gun shield of 6" thick was provided, partially to help balance the gun in its cradle. The turret ring was 74".
      NBC protection was available through a "kit" modification that was distributed to member nations upon request.
       
      Specifications, NATO Medium Tank:
       

       
      Crew: 4
      Dimensions
      Weight: 39.4 t
      Length (Hull): 7.2 m
      Width: 3.4 m
      Height: 3.05 m (without roof MG)
      Armament
      Main armament: 90mm T104E3/M56
      Caliber length: 62
      Tube length: 5.60 m
      Tube life: 500 shot
      Secondary armament: 1 × M1919, M60, MAG, MG3, etc GPMG
      Cannon ammunition: 65
      MG ammunition: 3200
      Elevation: +25/-12
      Penetration with T53 Shot, 10.9 kg at 976 m/s:
      100 m: 22.2 cm
      500 m: 20.0 cm
      1000 m: 17.9 cm
      2000 m: 14.3 cm
      Armor
      Upper Hull: 76.2 mm / 30 °
      Lower Hull: 76.2 mm / 45 °
      Rear Hull: 38.1 mm / 90 °
      Hull Roof: 25.4 mm
      Hull Floor: 25.4 mm
      Turret Mantlet: 152.4 mm / 90 °
      Turret Front: 152.4 mm / 90 °
      Rear Turret: 90 mm / 90 °
      Turret Roof: 50.8 mm
      Mobility
      Engine: Depends on variant, often AV-1790 w/ CD-850 transmission or Meteor with Merrit-Brown Z.51.R transmission. Variant with Ford GAA and syncromesh transmission also trialled.
      Displacement: Depends on variant
      Gears (F / R): Depends on variant
      Power to weight ratio: Depends on variant
      Top speed: Depends on variant
      Suspension: Depends on variant
      Fuel storage: Depends on variant
      Range: Depends on variant
      Track width: Depends on variant
       
       
    • By Collimatrix
      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.

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