Predetermined fires are used to cover target areas such as avenues of enemy approach, likely sites for enemy weapons, and probable enemy assault routes.
aiming point aiming point
range to break
BREAK 4N UNIFORM SLOPE
range to break
BREAK 4N UNIFORM SLOPE
A good FPL covers the maximum area with grazing fire. Grazing fire can be obtained over various types of terrain to a maximum range of 600 meters.
To obtain the maximum extent of grazing fire over level or uniformly sloping terrain, the gunner sets the rear sight at 600 meters. He then selects a point on the ground which he estimates to be 600 meters from the gun, and he lays, fires, and adjusts on that point.
If the gunner cannot obtain 600 meters of grazing fire because of a break in the terrain at ranges less than 600 meters, he determines the range to the break, indexes that range on his rear sight, and then lays, fires, and adjusts on that point.
To prevent enemy troops from crawling under the 1-meter-high grazing fire, a few mils of search (downward) should be applied to the elevating hand wheel on the traversing and elevating mechanism.
The extent of grazing fire and the extent of dead «pace may be determined in two ways:
In the preferred method, a gun is laid for elevation and direction (and cleared). A member of the crew then walks along the FPL while the gunner looks through his sights. In places where the soldier's waist (midsection) falls below the gunner's line of aim, dead space exists. Arm-and-hand signals must be used to control the soldier who is walking and to obtain an accurate account of the dead space and its location.
Another method is to observe the flight of tracer ammunition from a position behind and to the flank of the gun.
Predetermined targets, including the FPL or PDF, are engaged on order or by SOP. The signal for calling for these fires is normally stated in the defense order. Fires on predetermined targets may be controlled by arm-and-hand signals, voice commands, or pyrotechnic devices.
Machineguns fire the FPL or PDF at the rapid rate of fire unless the situation calls for a higher rate. When engaging other predetermined targets, the rapid rate of fire is used unless a different rate is ordered.
METHODS OF LAYING THE GUN FOR PREDETERMINED
The gun is laid on each target in turn. When laid on each target in the primary sector, the direction and elevation are taken from the traversing bar and the traversing and elevating mechanism. Both direction and elevation, as well as the range to each target, are recorded on the range card.
Another method for laying on predetermined targets is to use field expedients. These field expedients must be used in the secondary sector, and they can be used in the primary sector to aid the gunner.
The laying of the gun by either method may be verified by firing the gun and adjusting if necessary, by changing the data, or by moving the field expedients.
Steps to obtain direction and elevation readings are as follows:
Centering the Traversing Mechanism. With the left hand, turn the traversing handwheel TOWARD the gunner as far as it will go, then turn it AWAY two complete revolutions. This is the approximate center (50 clicks). This center may be found in the dark by counting the clicks.
To lay the gun for direction when an FPL has been assigned, slide the traversing slide all the way to the appropriate end of the traversing bar, so that metal-to-metal contact is made between the traversing slide and the tripod leg. Then, shift the tripod until the muzzle of the gun points along the FPL. If an FPL has not been assigned, lay the gun for direction on the center of the primary sector. In this case, lock the left edge of the traversing slide on the "0" graduation on the traversing bar. THE LEFT EDGE OF THE TRAVERSING SLIDE IS ALWAYS USED AS THE INDEX. Shift the tripod by moving the trailing legs until the muzzle of the gun is laid on the center of sector. Once the gun is laid for direction, emplace the tripod firmly by digging in the tripod shoes or by placing sandbags on the tripod legs. Whenever possible, the rear legs should be staked to increase stability and prevent accidental movement of the tripod. When the gun is not being used, it should be oriented on the PDF.
Recording Direction Readings. Direction readings to all targets in the primary sector of fire, with the possible exception of the FPLf are recorded on the range card. The FPL normally needs no direction reading because, in laying on the FPL, the traversing slide is positioned to the extreme right or left (metal-to-metal contact) of the traversing bar. The FPL is depicted in the sketch section of the range card by the extended machinegun symbol with a thick, shaded blade. Use the following procedure to obtain direction readings to targets other than the FPL:
Loosen the travei*sing-slide-lock lever and move the traversing slide along the traversing bar until the machinegun is laid on the center base of a point target and on either flank of a linear target.
Lock the traversing slide to the traversing bar and read the direction reading from the scale on the traversing bar. IF THE LEFT EDGE OF THE TRAVERSING SLIDE DOES NOT FALL EXACTLY ON A 5 MIL GRADUATION (TICKMARK), USE
THE NEAREST GRADUATION AS THE DIRECTION READING. The direction reading will be recorded as the direction in which the muzzle of the gun is pointing.
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