Photo G3157: PBR weapons system, Mk-18 Hand cranked 40 mm Grenade Launcher was mounted on a pedestal or rail on the aft deck between wheel house and 50 cal. machine gun. Courtesy of SP/4 Kenneth J. Marraccini, B Company & HQ Detachment, 720th MP Battalion, 89th MP Group, 18th MP Brigade, Vietnam, October 1968-December 1969.