M67 American 90mm Recoilless Rifle

The M67 recoilless rifle was a 90 mm (3.55 inch) anti-tank recoilless rifle made in the United States and later in South Korea. It could also be employed in an anti-personnel role with the use of the M590 antipersonnel round. It was designed to be fired primarily from the ground using the bipod and monopod, but could also be fired from the shoulder using the folded bipod as a shoulder rest and the monopod as a front grip. The weapon was air-cooled and breech-loaded, and fired fixed ammunition. It is a direct fire weapon employing stadia lines to allow simple range finding, based on a typical tank target bridging the lines once in range. The M67 is shaped like a long tube with the sight assembly and trigger offset to the side in opposite directions about halfway along the barrel. Under this point is the monopod, with the bipod halfway back from there. The weapon requires a crew of three to operate it; a gunner, assistant gunner (loader) and ammo bearer. The breech is hinged on the right side, and has to be swung open to load the round. It is then swung closed and when the rifle is fired, the rear end of the shell case breaks up and is blown out of the back of the breech block. On the left side of the barrel, near the sight and trigger assemblies, is an asbestos heat shield to protect the gunner's shoulder and neck from the heat of the barrel when firing. It is capable of maintaining a sustained fire rate of one round per minute, but the weapon could also be rapid fired at an increased rate of one round every six seconds (10 rpm) by a well trained crew. The rapid firing is limited to five rounds, with a mandatory 15 minute cool-off period afterward. The M49A1 sub-caliber device, which uses NATO 7.62 mm rounds, is typically used for zeroing the sight and for qualifying purposes. The sight is visually zeroed by setting crossed strings over the gun barrel opening (a rubber loop and notches at the end of the barrel facilitate holding the string in the correct position), then looking through the barrel of the sub-caliber device (and crossed strings) and setting the fixed stadia, reticle sight to the same target. The sub-caliber rounds can then be used to further refine the zero and to qualify.