This is a second pattern Bendix-Hyde carbine, made for the M1 Carbine trials. The first Bendix-Hyde had a number of features that Ordnance requested be changed (including a pistol grip), and this was the modified version submitted for the second round of tests. It lost out to the Winchester design, of course, which became the M1 Carbine.
I had a chance to take one apart at RIA, so I made sure to get a photo or two (click to enlarge):
The M2 Carbine was a mechanically simple modification of the M1 Carbine to allow fully automatic fire. The fire prototypes of the M1 Carbine had actually been selective-fire guns, but that requirement had been dropped […]
This is Lot 1106 in the upcoming October 2019 Morphys Extraordinary auction. The Marlin / United Defense US-42 submachine gun was not used by the American military, but it did see service in World War […]