The M50 Ontos AFV used by the US Marine Corps in the Vietnam War had six 106 mm recoilless rifles with .50 cal. spotting rifles on it. It was only lightly armored, and could be carried into position by a helicopter. Even though the Ontos was designed as a tank destroyer, the USMC in Vietnam found it to be a very mobile and effective direct fire artillery piece, and apparently the Viet Cong would run at the sight of one of them. All six of those barrels firing anti-personnel flechette rounds at once would definitely be a human lawn mower.