The M1-A1 folding stock carbine was a weapon unique to the paratroops in WW2. Manufactured by the Inland Arms division of General Motors, this weapon utilized a small, specially designed .30 caliber bullet which was considered a compromise between a pistol and a rifle. The side-folding stock of tubular metal has a leather cheek plate on the left side. Early models were made without a bayonet lug. The carbines, which were usually issued to officers and men assigned to crew-served weapons like M.G.s and mortars, were the subject of many complaints. They lacked knockdown power, even at short range, and were frequently discarded in disgust.
http://www.101airborneww2.com/index.html