Attempting to Fulfil The Plan: ISOT Edition

The Peoples SMG
APSM-13 (Automatic Pistol of Sophie McDonald)

Taking cues from previous work on the development of cartridges, the step towards a simple automatic design has been a focus of much debate, as the increased complexity of the mechanism has limited work. Designing off of initial proposals for the STEN and committing towards several important simplifications, the gun itself can be produced in as simple and reliable of a manner as possible. Practically every aspect of the design will be limited by shortfalls in machining and personnel of minimal quality to build it, but that doesn't mean that it cannot or should not be done. These same rationalizations have been made before for wartime expedient SMGs that went on to perform for decades and they can be done again.

As an added benefit, experience built in the programs towards the construction of simple blowback mechanisms can directly contribute to more complex and capable systems, including the eventual design of a dedicated machine gun for rifle caliber work along with issuing a new actual assault rifle capable of replacing both the proposed bolt action rifle. For now though the first of the many rationalizations to make this a functional gun must be explained, and that is the simple blowback system of feeding. The primary driver for new cartridges to be fed in will be a single large spring, fixed into the backplate by a removable guide and attached to a machined monolithic piston. A small hole will be made in the side to attach the cocking handle while the extractor and the feed mechanism will be machined into the cartridge face of the piston.

For efficient cartridge extraction, a small spring and latch will be fitted into the piston, enabling it to feed in a new cartridge and reducing the probability of any failure to extract. Unlike the original STEN, a bottom-fed magazine has been judged as optimal for ease of carrying, and to provide a grip surface so as to enable control with a more powerful cartridge. Despite the increased complexity in the design, a thirty-round dual-stack magazine was still prioritized, as while it would require a quality spring, so would any reasonable single-stack design. In combat issuance, the troops are only expected to get 2-3 magazines anyway, with the expectation of reloading them from clips in the field. To enable this, a fast-loading notch on the back of the magazine is expected to be stamped in.

Below the main upper assembly with the piston, a simplified trigger assembly will be constructed. The lower assembly will be built with two stamped pieces of metal, one forward cover to protect the trigger assembly, and one to provide physical protection to the trigger and form a quasi-pistol grip. Going from bolt facing to finger facing, a spring along with a bolt retainer will be the first component, made out of a small piece of stamped steel with pins fitted and secured with pins to the front assembly. The top of these pins will retain the piston in a ready-to-fire position using the tension brought on by a set of two springs on the bottom pin. Once the trigger is depressed a small stamped latch will release the mechanism, driving forward the piston and firing.

If firing, the released bolt then slides forward using the main spring, striking the cap of the cartridge. This then fires the round and causes the bolt to slide back, extracting the brass using the movement and taking advantage of the magazine spring by "catching" the round on top of the magazine. After the piston finishes its slide back, the newly caught round strikes the firing pin providing the recoil energy to repeat the cycle and maintain automatic fire. In a semi-automatic fire, a moderately sized pin going through the trigger assembly can be used to ensure that the bolt retainer catches the bolt and cannot recycle on its own until the trigger is pressed again.

To take advantage of the longer and higher pressure round expected to be issued, and to provide assault troops with some ranged options, a 300mm barrel has been selected. This will be screwed into the firing chamber assembly, providing a solid fixture. A simple thin stamped hand guard will go over the barrel, adding some weight, but ideally preventing at least a few burns from contact with the barrel, and providing a mechanical buffer to protect the important central assembly to which most things are connected. The physical back cover of the gun will consist of a simple piece of stamped steel, with a j-hook punched out of it to act as a safety for the weapon when not in use.

Taking advantage of the experienced woodworkers from the crossbow program, a simple set of wood furnishings can be made to provide a solid stock. While a folding metal one could be made, the sheer quantity of experienced woodworkers available allows for a larger and more stable one to be made. The enlarged stock is expected to help significantly with comfort, and on the chance that the weapon is used in melee or rough conditions, can provide a bit of heft and durability. A standardized bayonet cup will be available to be fixed to the barrel-barrel shield assembly, providing further alternative options if all else has failed with the gun.

Sights are expected to fit into a notch on the rear and front of the gun, allowing options for adjusting for ranged combat by the replacement of the simple stamped metal rear block. This isn't expected to be necessary at any reasonable combat range, but this simplification of the sites does allow for a massive reduction in machining complexity. Complicated work is only expected to be needed on the bolt itself, with all other components of the gun being stamped or punch pressed. A conscious effort to minimize the need for springs has also been made, allowing for a gun that can still perform while being as simple as possible to manufacture.