A Troop Reflections on the Mortar
The 81mm mortar consisted of three main parts, the tube, the bipod and the base plate. Each part was carried by the three member crew in an infantry platoon. Photo of mortar ground-mounted showing base plate
Go to web page showing Mortar rounds
The high explosive round could be set on HE quick or HE delay. The quick setting was the default. The delay setting was used in a canopy type jungle or for dropping the round on a building. The round had a slight delay for detonation. There were 9 bags of powder on the bottom of the round, just above the fins. Charge 9 had a range of over 3 miles and charge 0 could be dropped at very close range. The bags were ripped off and discarded during a fire mission. The tube had a smooth bore with the firing pin anchored in the bottom. Because of the smooth bore, fins were used to stabilize the round in flight. The round was simply dropped down the elevated bore. The primer contacted the firing pin causing the charges to ignite propelling the round down range in a high arcing flight.
The bipod was used to elevate the tube. The mortars in the APC were mounted on a turntable for 360 degree rotation. The range was determined and a chart was consulted as to the elevation and charge required. The sight was set to the corresponding number and the bipod was cranked up or down to level the bubble on the sight. Bracketing was then used to hit the target. Night shooting or H & I was usually shot at low charge and close in. During that type of firing, the sight was really not needed.
Illumination rounds were fired the same way except the nose piece contained a timer. The distance was determined and looked up on the chart. The information given was the charge, elevation for the sight and an amount of time to set the fuse. The round would fly until the time elapsed causing the parachute to deploy and the charge to detonate, illuminating the area.
During operations as a company or where coordinate firing was required, the use of the aiming circle and plotting board were required. The aiming circle was set up and orientated to due North. The mortars were then sighted on the aiming circle so each on was pointing the same azimuth. Aiming stakes were then set out and aligned with the sights on each mortar. The plotting board had the coordinates of the tubes and the target could be plotted. Using the board, direction (deflection) and range to target was found. The deflection was entered on each mortar sight, the tube turned and realigned with the stakes. Elevation was entered and both bubbles leveled. The chart gave the gunner the charge to set and the rounds were fired. The mortar when used in this manner was similar to an artillery cannon except with much shorter range.
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