This junior 'noncom' is carrying his M3 'Grease Gun'. This cheaply-made submachine gun was manufactured out of stamped and welded steel parts and looked remarkably like a mechanic's grease gun, hence the nickname.
It fired only in automatic mode and came with a 30-round straight magazine. Because of its small size it could be fitted easily inside the confined space of an M4 Sherman.
Like the previous Tank Sergeant our Corporal is outfitted with the same Tanker's uniform plus helmet and goggles.