So, in the time between the suppressor design that I am doing for work, I decided to go after a semi clandestine manufactured SMG. The criteria driving the design is that round tube is incredibly common in SMG designs, so I wanted to avoid that and use rectangular tube and bar stock. This minimizes the operations that require a lathe, and while they ideally would be done on a mill, they can be accomplished with a drill press and hand tools if you have the patience. Some of these parts are innocuous enough that they could also be farmed out to local machine shops without raising eyebrows. Strangely, one of the larger issues that has faced clandestine small arms manufacturing is an acceptable human interface. Other people solve this by traditional methods such as carved wood grips, or cast/molded plastics, but that is a time consuming process to make a part that should be very simple. My solution was to use handlebar grips from a bicycle. They are already designed to provide a griping surface for your hands, and they are common enough and varied enough that you could will not have a problem sourcing them.
As far as the design goes, it is still a work in progress. The receiver is pretty much dialed in, as are the trunnions, the barrel, barrel retention system, etc. The FCG has been a sticking points, as designing them is probably my greatest weak point when it comes to arms design. As the FCG is horribly incomplete, the bolt may similarly undergo changes. It is currently planned to have a linear hammer, but that is still in the works. I have only begun to consider what to do for the stock, and the forearm will probably come last. The design uses Uzi magazines, and I'm toying with the idea of being able to change magazine compatibility by having alternate lower receivers.
There are two primary versions; the 9" barrel original design, and the 5" barrel design.
Charging handle/bolt/action spring interface
Early receiver, designed to be cut out of 1x2" 11ga rec steel tube. The notches near the trunnion and front barrel support are to allow the components to be welded together.
charging handle and barrel retention system details. The action spring guide rod runs through the front barrel support and in conjunction with the receiver it locks the barrel retainer plate in place. The retention plate slips into a grove cut into the barrel. This prevents the barrel from moving backwards out of the receiver, while the square section at the breech of the barrel nests in the trunnion to prevent forward movement. The barrel is not rigidly fixed to the receiver, but this is acceptable considering the intended applications of the weapon.
I woke up one day and decided "why not design an entirely new rifle from scratch, and live blog it?" So here we are.
About ten minutes in and we've got the beginnings of a receiver extrusion made from 7075 T6 aluminum:
Currently I think the rifle will be in 5.56mm. It will not use STANAG magazines. @Ulric plz halp design new mag?
The year is [year]. You are a [thing] designer working in/for [country/nation state/corporation]. The [things] of the rival [country/nation state/corporation] have recently *gotten meaningfully better in some specific way* and/or *the geopolitical and/or industry circumstances have significantly changed*. You have been tasked with designing a [thing] to meet the needs of this new and changing world!
If that made you laugh, maybe you've participated in a design competition before, here or on another forum. I've been a contestant or judge five or six design competitions by this point, and I'd like to highlight a mistake I've seen people make often that I think could hurt your chances. And that is, designing something for the wrong time period, specifically designing something that is too early for the period in which the competition takes place.
Quick: When you think about US rifles in World War II, what comes to mind? A lot if you would answer with the M1 Garand, I'd bet. If I went on another forum and started a "Design a Rifle: USA 1944" thread, I bet I'd get a lot of entries that took their cues from the M1 Garand - but the M1 wasn't designed in 1944, it was designed in the late 1920s. In attempting to "fit in" to the time period of the competition, they would have in fact submitted a design that is 15 years too late! The an appropriately dated entry would be something like a T25 Lightweight Rifle, which is associated mostly with the late Forties and early Fifties, but whose design began in the mid 1940s. Using the M1 Garand as a model for your 1944 design would result in something like a slightly refined Garand with a box magazine slapped on, putting you well behind the curve!
The T25 was what 1940s designers thought the rifle of the future would look like. Keen SHitters will notice the joke about the M14 in the above paragraph.
Tanks and other vehicles are the same way. The M48 is associated with the Vietnam era, but its development began in 1953. The Space Shuttle is associated closely with the 1980s, but design work on it began in the late 1960s, before the first man ever set foot on the Moon. The MiG-15 is associated with the Korean War, but Soviet jet fighter designers at that time were already putting pencils to paper on what would become the MiG-21.
It's tempting to create a design that looks like it would fit right in to the battles we know and associate with whatever time period a competition covers. Yet, the real-world designers fighting those battles from their drafting tables were already imagining the next thing, and even what would come after that, in turn. Design competitions are just for fun, but in some ways they are also practice for the real thing, so don't get stuck in the past!