I've got another weapon Gun Jesus has done videos on that I don't think Paul's got on his website. It's a submachine gun, chambered for 9mm Parabellum, developed just after World War 2 to use surplus Sten magazines. So far, so conventional.
It's a simplified Sten. With a bullpup design. And a wood body. No foregrip. No semi-automatic fire. No trigger guard. No sights. Yes, it's the wacky and WTF-inducing
Viper Mark I.
Because of the utterly bizarre firing method, I went with a range halfway between a bullpup and a pistol of otherwise identical configurations. The buttstock under the shoulder should give a more solid anchor than a pistol, but the lack of a handgrip for a third point of contact and the complete lack of sights make it less effective than a rifle. Also, this gun can only take Quick Shots, not Aimed Shots. It uses a shortened Sten magazine because the full-length magazine was unwieldy with this design, but as far as I know there's no physical reason it can't use the 32-round magazine.
Viper Mk.I (9x19mm Parabellum)
Wt 2.1 kg, ROF 5 (no SA), Dam 2, Pen 1-Nil, Blk 4, Mag 20, SS N/A, Brst 5, Rng 40
The
Viper Mk.III is somewhat more conventional, with a metal body, normal buttstock, and sights. It also switched from a Sten magazine to an MP40 magazine. A push-through lever/button takes the gun from safe through semi-auto to automatic fire. It had screw-off barrels in 4.7", 6", and 7.5" lengths. The stats below are with the 7.5" barrel.
Viper Mk.III (9x19mm Parabellum)
Wt 2.21 kg, ROF 5, Dam 2, Pen 1-Nil, Blk 4, Mag 32, SS 2, Brst 5, Rng 60
ETA: I think these work particularly well as examples of things that might be produced during the fragmented years when isolated areas are trying to produce firearms for self defense, particularly the Mark I. What's essential (the receiver; the barrel; the trigger system) is simple but effective, and what's not essential (the shell; sights; safeties; selective fire) use non-strategic materials or are simply eliminated. It's almost a real-world equivalent of the M-16EZ, using spare parts to create a gun that's crude but better than nothing.