As far as I know, this gun never received an actual name, but in the 1950s Winchester was working on a cheap and simple submachine gun in 9mm Parabellum. It fired from an open bolt, and had a folding stock that could be used as a forward handgrip in its stowed position, clipping to a bolt under the muzzle. It used leftover MP 40 magazines, although I imagine if it had been adopted an early update would have seen it adapted for use with Uzi magazines.
The Armourer's Bench noted it has a 7.5" barrel, which is the only measurement I could find for the gun, so everything else is calculated by FF&S based on being a light automatic firearm using 9mm Para from a 7.5" barrel.
Winchester "Burp Gun"
Wt 1.85 kg, ROF 5, Mag 32, Dam 2, Pen 1-Nil, Bulk 4, SS 2, Burst 5, Range 70
I'd probably adjust the range down to around 50 or so, since FF&S is very enthusiastic about the range of pistol-caliber firearms with shoulder stocks. As a one-handed weapon range would drop to 21, which I'd increase to 25 considering the availability of the front grip.