Biwarip machine carbine

On the 5th of August 1938, the Small Arms Committee in Britain was made aware of a new submachine gun which they recorded in their minutes as the "Biwarip machine pistol". This was said to be a lightweight, simplified 9mm submachine gun that was ideal for parachutists, firing from an open bolt blowback action with an adjustable fire rate (600 rpm by standard) and a fire selector switch. The horizontal magazine feed took 30-round box magazines. It could be fired from the shoulder by fitting a detachable buttstock to the bottom of the pistol grip, or fired freely from one hand like a pistol. There were no sights on the gun but there was a bayonet mount on the right side of the barrel casing. The SAC report commented that "the production costs of the weapon are very low as compared with those of other automatic pistols [submachine guns]".

Unfortunately, there are no recorded details of the origin, designer, or manufacturer of the Biwarip submachine gun. Even the name that the SAC recorded is questionable. The Committee commonly misspelled the names of foreign submissions, as the transcription was done probably by ear, and therefore it is likely that "Biwarip" - which doesn't seem to mean anything in any language - is likely a corruption of another word or name. The place of origin is also unknown; it has been assumed to be British by some sources, but the SAC did not actually specify that it was. In some aspects, this gun resembles a modified version of the Swiss Solothurn S17-100 submachine gun. The receiver and barrel are similar; the bayonet mounts in the same place; and the magazine feed is canted forward much like the Solothurn submachine guns.

The SAC was not interested in the Biwarip submachine gun and declined to purchase any samples for testing. As far as is known, it never achieved any sales, and quickly after the beginning of the Second World War it disappeared into complete obscurity. The concept did, however, have great merit, as many of the principles noted by the SAC to be present in the Biwarip would later become integral to the design philosophy of the Sten gun.