STEN Gun History and Blueprints

sten productionIntroduction

A number of guns interest gun enthusiasts all over the world, from well-known names such as AK-47 to lesser known but still unique options such as the STEN gun.

Some gun aficionados choose to purchase these guns—where legal—and others opt to build them at home. However, keep in mind that it is technically illegal to build a fully-automatic firearm in the United States, so be sure to stay within the confines of the law to avoid fines and possible jail time.

History of the STEN Gun

The STEN gun is one of the more unique collectible ideas for gunsmiths, and a real challenge to build from blueprints. Not to be confused with the popular law enforcement/self-defense weapon called a STUN gun, a STEN gun was a gun used by military personnel in Britain and British Commonwealth regions during the eras of the Korean War and the Second World War in keeping with trends set by Americans with the Tommy gun.

During the 1940s, when they were first mass-produced, roughly 4 million of the STENs were made for military distribution. STEN is actually an acronym derived from the names of the gun’s original designers, Major R. Shepherd, Mr. H. Turpin, and the company known as Enfield.

The design of the STEN closely resembles another British gunsten—the Lanchester submachine gun utilized during this period by the Royal Navy—but it is also remarkably like the German MP28.

The Lanchester and STEN magazines, being similar guns from a design/functionality perspective, were actually compatible originally, although the Lanchester’s magazine had a 50-round capacity and the STEN had a capacity of 32-rounds.

British and Commonwealth personnel used the weapon from its inception in the 1940s until it was replaced in the 1950s, and the gradual phase out was completed by the 1960s in both regions. Four different versions, called Marks, of the STEN were created, but the STEN Mark II is one of the most common and Mark IV was never actually released.

STEN Gun Original Manufacturer/Designer

The original design of the STEN was quite simplistic, incorporating basic stamped metal parts and involving only minor welding for a minimal amount of machining or manufacturing time in essence. This enabled even smaller shops and factories to create the weapon efficiently at the Enfield location, with the STEN Mark III taking only five man-hours from start to finish.

As a matter of fact, the STEN’s cheaper models were fully functional using fewer than fifty parts total, giving it its distinctive bare-bones look. Mark I was probably the least bare-boned Mark design, although the Mark V (which did not make it to production until after they were being replaced) was considered a higher class of weapon than previous models.

During the course of its production, the STEN changed and received many different obvious and subtle design modifications. One of the most notable was to the Mark IV, which decreased the likelihood of accidental discharge due to an intrinsic cocking handle flaw.

Some of the less obvious design changes dealt with product reliability or production/manufacturing efficiency. They were, overall, considered effective weaponry, even amidst all of the allegations of defective, problematic, unreliable models for years.

Method of Operation—STEN Gun

The STEN’s designed features a blowback-operated firing mechanism with an open bolt and a stationary firing pin on the bolt’s face. No breech locking mechanism is present, so the bolt’s rearward movement caused by the recoil impulse is blocked solely by a mainspring and the bolt’s own inertia.

The basics of the STEN were similar to the German MP40, Russian PPSh-41, US M3 submachine gun and numerous other designs, but this included both similar attributes and faults.

There were a host of problems and shortcomings related to STEN gun firing, and many different ways that the gun could malfunction without warning. Stoppages and carbon buildup caused a firing failure, and firing the STEN by handling the magazine with the supporting hand caused significant wear to the magazine catch. If a STEN had a feeding jam due to magazine cartridges, it had to be cleared and restocked before it could be fired again.

STEN Gun Plans/Blueprints

sten mark 2As before mentioned, most average gunsmiths lack the proper equipment for a fully-functional STEN gun, because it requires the ability to build and implement a bold that fires as a closed-bolt gun.

In addition, the weapon cannot be owned without approval from the BATF and a fairly large tax stamp in addition to other local, state, and federal law compliances.

Make sure to get the blueprint/weapon approved prior to beginning the project to avoid these and other penalties from the government, especially those who do not or cannot for whatever reason have the right to own a firearm in the United States.

There are semi-automatic kits available for building a STEN gun, but the experts claim that they are prohibitively priced. In fact, they say that it is just as realistic to purchase a kit to build an assault rifle as a historically-accurate STEN gun. The primary benefit for gunsmiths is that it is easier to legalize the semi-automatic version for those who have that concern.