It fired full-sized 30-06 cartridges and weighed nearly 20 pounds. The various sub machine guns in the US WWII arsenal (Some Thompsons, some British versions and some of the later "Grease Gun" design) mostly fired 45 ACP pistol ammunition, same as my Colt model of 1911 semi-auto pistols; stopping a 45 ACP bullet was no big accomplishment for armor, because the round nosed bullet only travelled at 770 feet per second, whereas the pointed bullets from a 30-06 travelled at 2700 fps in the armor piercing version, and 2900 in the lighter bullet version.