The Welgun was a prototype submachine gun developed by the British unconventional warfare organisation, the Special Operations Executive. Although it performed well in tests, it was never adopted, and was produced in small numbers only.
The Welgun uses a fairly conventional blowback design. It used the same 9x19mm Parabellum cartridge as the Sten. Since this round was also used by the Axis, resistance fighters could obtain ammunition from enemy sources. The Welgun used the same 32-round single-feed magazine as the Sten, a potential source of trouble as this design was unreliable in service. The magazine fed vertically, rather than sideways as in the Sten.
The Welgun had a folding stock. When this was folded to lie over the barrel and body of the gun, the overall length of the weapon was barely 10 inches (25.4 centimeters), allowing easy carriage and concealment. The Welgun also had a wooden pistol grip, and vestigial wooden foregrip, which contributed to its accuracy and balance.