The M3 "grease gun" was one of the simplest, ugliest, and cheapest personal weapons ever fielded by the U.S. military. But, as one U.S. Marine combat veteran recalled, what this crude submachine gun lacked in looks, it more than made up for that with brutal effectiveness. THE GREASE GUN is a compact weapon with an overall length of 29.8 inches with the stock extended and 22.8 inches with the stock collapsed. The barrel is 8 inches long. The 8.15-pound empty weight of the gun is brought up to 10.25 pounds once a loaded magazine of 30 .45 ACP rounds is...