In the last decade, Stoner’s evolved AR-platform has been pressed, stretched, pulled, prodded, and modified. Many consider it a panacea among firearms, although its suitability in certain roles is certainly a matter for debate. Nonetheless, the concept of modifying existing weapons to meet specific, often highly specialized needs is not new. Many nations have experimentally modified their standard service weapons over the years. Britain, for one, with a long history firearms innovation, has fielded many successful modified weapons in its modern history.
During World War II, Britain’s rapid and heavy investment in special operations created demand for specialized equipment. From 1940 to 1945, a continuous flow of extremely imaginative products vied for adoption. Some of the prototypes were outlandish and never made it past an initial review, while others, including several innovative weapons and weapon modifications, were quite successful and had careers that lasted well beyond the war.
Following its victory against the Luftwaffe in 1940, Britain found itself short of virtually everything, and not just with regard to its military. For instance, Britain could not sustain itself with domestic agriculture, and had to import a large percentage of the food required to maintain its population. Austerity became a byword by default, and the STEN submachine gun was a product of that austere time.
The STEN was of remarkably simple design compared to the Thompsons and Lanchesters that otherwise equipped British troops. It was also inexpensive, costing only around three pounds sterling to produce in its most basic form. Further, the STEN was easy to make, maintain, and use. A rather heavy bolt and recoil spring limited its rate of fire to a controllable 550 rounds per minute, even with hot 9 x 19 mm ammunition. Other basic marks of the STEN were a wire or skeletonized stock, a simple receiver template of flat steel that was cut and rolled into form, and then welded, and a firing pin that was actually a bump milled into the bolt instead of a separate pin-and-spring assembly. Virtually any factory could make the STEN, limited machining ability notwithstanding, and in the postwar era the STEN was produced in government- and privately owned factories around the world. Moreover, homemade STENS were de rigueur in guerilla movements through the 1960s, and some of the best came from the Jewish paramilitary organization, Haganah.
The foremost drawback of the STEN was its magazine. STEN magazines were and are notoriously problematic. The way to determine which ones will work in a specific gun has always been to load and test a number of them, keep the winners, and pass the no-go pile along to the next fellow! If you’ve ever gone through a knee-high pile of surplus STEN magazines, you have most likely experienced the sense of potential, and appreciated the multitude of both recognizable and mystery manufacturers that have contributed to this firearm’s history. A secondary, but still very significant, drawback of the STEN was its questionable reliability and inaccuracy. Compared in this regard to the Thompson, the MP 38/40, and even the PPSh-41, the STEN was clearly inferior.
The most refined STEN was the Mk V airborne variant, with its wooden stock, pistol grip, and vertical foregrip, as well as a bayonet mount. While none of those attributes fixed the STEN’s reliability problem, they did make the weapon more robust, and the ergonomic enhancements arguably improved its accuracy. It remains unclear whether anyone put the bayonet mount to use, or even seriously considered doing so. Regardless, later submachine guns, such as the Uzi, also included this feature.
At least two variants of the STEN were integrally suppressed for use in clandestine special operations: the Mk IIS and the Mk VIS. Both variants used a ported barrel, onto which a specially designed suppressor was fitted. If this sounds familiar to you, it’s probably because the renowned MP5SD is similarly designed. Unlike the MP5SD, however, the suppressed STENs were not particularly successful. It was not that the suppressor worsened the gun’s already mediocre reliability, nor that there is sufficient data to support any claim it impacted accuracy. Rather, the integration of a suppressor created entirely new problems: most notably, consistent overheating, which could only be averted by keeping bursts extremely short or only firing one round at a time.
We may wonder if the STEN’s overheating problem was due to its use of submachine gun ammunition instead of standard 9mm ammunition. While the MP5SD ultimately won an excellent reputation, it was plagued for a short time with problems resulting from the use of 147-grain subsonic ammunition instead of the hypersonic ammunition for which it was designed. In a related way, perhaps less powerful pistol ammunition would have solved the suppressed STEN’s problems. To date, the author has not uncovered any information to substantiate this, but it certainly warrants further research. Nevertheless, the Mk IIS and Mk VIS suppressed STENs were used by Britain’s Special Operations Executive, and by virtually all British special operations units, with some success. These two models were the only suppressed submachine guns in somewhat regular use during World War II — a fact that arguably confers some merit upon them, and certainly made them trendsetters.