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How WWII Changed Submachine Gun Design

How WWII Changed Submachine Gun Design 

Submachine guns, today considered one of the fundamental categories of small-arms and a staple of military and police forces, were once not taken seriously as weapons. But the world powers gradually warmed up to them and started experimenting. But it was during the Second World War that they were first put to extensive use, but only after a massive change in their designs that would forever change the idea of what a submachine gun was, and how it would be used. 

Submachine guns are a type of shoulder-fired firearm that is fully-automatic or select-fire, and fires a much smaller pistol cartridge, rather than the more powerful intermediate or rifle cartridges that a typical machine gun would use. At the start of the 20th century, martial forces would have not considered any such weapons suitable for infantry use, because combat at these times consisted of engagements at longer ranges, where firing powerful cartridges with heavy bullets was of peak importance. Rifles of the era would have iron sights calibrated up to thousands yards, and long barrels to afford the best long-range accuracy and highest velocities. Special roles like artillery crews, however, did not need nor want the large rifles, so they got specially designed pistols instead. These pistols had longer barrels (like the 200mm barrel of the “Artillery” Luger, as opposed to the 120mm standard barrel), and detachable stocks that sometimes even doubled as a holster, as in the Mauser C96. These stocked pistols were the first seeds of the idea that would lead to the submachine gun concept around the end of the first world war. 

Once WWI plunged Europe into chaos and conflict, the military powers soon found themselves entrenched and stalemated. The conflict presented a unique tactical challenge; their classical high-powered rifles they had chosen to arm themselves with were doing just fine for sniping across no-mans-land, but everything changed as soon as they went “over the top.” Now soldiers had to get across as quickly as possible, because any delays would increase their chances of just being cut down by the enemy’s heavy machine guns. If they did make it to the enemy trench, they now found themselves in a very different tactical environment, and their rifles were not an ideal tool any more. 

Their power was excessive at such close range, their length made maneuvering through narrow trenches difficult, manual operation meant you really only got one shot and had to hope you encountered enemy soldiers one at a time, while low ammunition capacity left the soldier constantly vulnerable while reloading. Responses to this problem were slow and mostly unhelpful, however. There was some experimentation with putting larger magazines on the standard rifles, but otherwise nobody was quite sure how to solve this problem. Eventually it would be the Germans who would work out the solution: the submachine gun. German arms designer Hugo Schmeisser, working with other influential designers like Theodor Bergmann, developed the world’s first real submachine gun to see service, the MP-18. It had all the characteristic features, being chambered in 9mm Parabellum, a pistol cartridge, and firing fully automatically from a 32-round drum magazine. However, the war ended soon thereafter, before it could have an actual impact on the war. But the cat was out of the bag now, and the world quickly recognized that submachine guns would be very influential. 

Throughout the interwar period, the submachine gun became hugely popularized in police and civilian use, but it’s important to note that the design didn’t substantially change during this period. This is where guns like the Thompson Submachine Gun and the Steyr MP34 were developed, and their styles matched the MP-18. Like the MP-18, these interwar SMG’s were heavy, machined from solid steel, with carefully cut, oiled, and polished wooden stocks. They were elegant weapons, made with care and quality and tight tolerances just like the rifles and pistols they were replacing. Alas, this quality construction gave them a hefty price tag that kept military stockpiles small right up until WWII. 

When WWII broke out, the world once again ramped up their arms manufacturing, and realized that now, in time of war, they needed those submachine guns, and they needed them immediately. But the elegant and carefully machined SMGs that had been developed thus far were too expensive and took too long to make. A huge change needed to be made to simplify these guns massively to allow for mass production. The major powers of WWII all developed new submachine guns to these ends. Germany, still ahead of everyone else, beginning their simplification program in 1938, went from the MP28 and MP34 to the MP38 then the particularly legendary MP40. The US started the war with the Thompson, but soon transitioned to using the M3 ”Grease Gun.” 

The Soviets started with the PPD-40 but moved to the PPSH-41. The British were importing the Thompson at great expense initially, but following the disaster at Dunkirk very quickly put together a series of austere SMGs, of which the Sten Mark II was probably the simplest submachine gun of the war and the best example of this paradigm shift. These new SMGs were hilariously crude; they had ditched the wooden stock in favor of a simple stock made from crudely welded steel tubing or even just bent wire, the receivers were simple steel tubes with little more than a slot cut in the side and some threads, they fired from an open bolt to simplify the fire-control groups, and the metal was often Parkerized instead of blued, leaving a functional but very ugly finish. The Sten gun, going from idea to production in mere months, didn’t even have a real grip, leaving the soldier to awkwardly hold their hand against a small wedge of sheet metal edgewise! 

The simplicity allowed parts to be made in almost any workshop and shipped to an assembly facility, rather than centralizing all production in major factories, which further improved the ability of nations to rapidly ramp up production. While not particularly well-liked by most soldiers, it’s hard to argue when the Sten gun represented a savings of over 90% over the Thompson SMGs Britain was importing before. 

A question raised, then, is why the Submachine gun was able to be so dramatically simplified, while main infantry rifles were mostly kept the same? The answer boils down to physics and engineering. The light cartridge of the submachine gun enabled a method of operation known as ”blowback” operation. This is a design of firearm where the gun cycles when pressure within the cartridge pushes directly against the face of the bolt, pushing the spent case and bolt rearwards. The bolt will then be pushed back closed under spring force, loading the next round to be fired. This can’t be done with rifles because the cartridges are too powerful, and would blow the gun open far too quickly, resulting in case-head ruptures. It was also infeasible in all but the weakest of pistols because blowback designs require very heavy bolts that would be excessive in a pistol. Semi-auto rifles and most pistols thus required locked-breech designs, where additional parts would work together to lock the bolt so it couldn’t open until a few milliseconds after the gun fired. This can be accomplished in myriad ways, and arms designers have tried thousands of them, but they all require many more moving parts and tight tolerances to be reliable. 

Submachine guns were large enough that the bolt weight wasn’t an impediment for the user but small enough that blowback could still work, making them ripe for dramatic simplification. The other primary element that allowed this to happen was the fact that these guns were operated open-bolt. This means that when the gun wasn’t firing, the bolt would be held open, rather than closed. What sounds like a small change, in fact allows for even more simplification, because if the bolt is rapidly closing just before firing, then the firing pin of the gun could simply be fixed to the bolt face, rather than using a separate firing pin and hammer, each with their own springs. So that’s 4 more moving parts eliminated just by moving to a fixed firing pin. The trigger now can simply grab the bolt when it’s at it’s rearmost position to stop the gun from firing, and just let it go when to fire. This simple function can be done with just one part, the trigger itself also being the sear and functioning as a simple catch against the bottom of the bolt. This leaves very few moving parts, allowing for loose tolerances and blazing fast manufacture. 

This radical simplification didn’t quickly reverse course after WWII ended, however. The guns were made a bit more comfortable, with things like actual grips added back on, but otherwise the idea of very cheap stamped sheet metal construction and open-bolt blowback operation stuck around, with only simple substitutions like using polymers instead of metal where possible. Even today, consumers expect submachine guns (or their civilian-legal counterpart, the “pistol-caliber-carbine”), to be substantially cheaper than a typical rifle because of the legacy left by the WWII rapid simplification of the SMG. Ultimately the only people to buck this trend were once again the Germans, who developed guns like the MP5, which used more complex roller-delayed actions. 

These were marketed as elite weapons for wealthy nations’ special forces, SWAT teams, etc. But even these still used stamped sheet metal receivers. In fact, as technology improved, engineers found ways to apply the same principles they learned in SMGs to other types of firearms as well. Assault rifles soon came around using the same stamped sheet metal construction, and full-power battle rifles like the G3 and the FAL were built the same way. The revolution in SMG design had boiled over into all areas of small-arms design, and touched every part of the industry in the next few decades. 

The submachine gun came into military use slowly at first, then all at once, bringing along an overwhelming degree of simplification. While their initial complex forms based on traditional techniques would last for nearly two decades, they were transformed in just a couple years into to guns that were little more than a few parts and springs stuffed in a pipe, and the legacy of this rethinking of their designs can still be seen in modern small arms design across all categories. 

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