Check Of Accuracy And Adjustment Of Automatic Rifle Procedure For Adjusting Rifle

The accuracy is checked:

I* When the^ri'fles arrive afvxt?e using units;

2« After replacing the front sight or after repair of the rifle;

3. When abnormal fire dispersion is discovered during fire. k

The best riflemen of the unit must be selected to fire the rifles for the purpose of checking accuracy. The riflemen are detailed by the company commanders. The rifles are fired in the presence of the soldiers to whom the rifles are assigned, and im the presence of their commanders»

Before firlag for tasting accuracyp the rifle must be carefully Inspected and all defects must be eliminated. The armorer-artificer must be preaemt at the firing range.

Firlag for testing accuracy must be performed under favorable conditions: in clear» calm weather, in a protected rifle range, or on a portion of a rifle range which is protected from the wind. The rifles are fired for accuracy using ball a—iiition at a range of 100 m with the rear sight set on graduation

The target in this case is a black rectangle 35 cm high and 25 cm wide, fastened on a white board 1 m high and 0.5 m wide. The aiming point is the center of the lower edge of the rectangle; it should be located approximately at the height of the head of the soldier firing the rifle« A point located above the aiming point on the vertical line which characterizes the normal position of the center of the impact, Milch should be above the aiming point by 28 cm, is marked using chalk or pencil.

The point thus Harked is the control point*

The rifle is fired in the prone position using a support. The support may be a bag which is filled with sawdust, earth, or sand«

In this position, the left arm of the rifleaan, which is supporting the rifle, should be on top of the support.

Figure 89. Determination of center of impact by the graphical method.

I - measurement of four holes; II and III - measurement of four symmetrically located holes.

Four single shots are fired while carefully and uniformly aiming at the lower edge of the black rectangle, and the position of the rifleman's body and left hand must not change.

When fire ceases, the commander inspects the target and determines the accuracy of the rifle and the position of the center of impact on the basis of the location of the bullet holes. The accuracy of the rifle is considered to be acceptable if all four bullet noles, or at least three holes, if the fourth hole is located quite a distance away from the remaining holes, are grouped in a circle with a diameter of IS cm, and if the center of impact deviates from the control point no greater than 5 cm in any direction.

If the accuracy does not satisfy this condition, the company commander must inspect the rifle, check the sight setting, and repeat the fire. If an unsatisfactory result is obtained the second time, the rifle is sent to the repair shop for ascertaining and eliminating the causes of inaccuracy*

If the accuracy of the rifle is considered normal, the commander determines the center of impact and its position with respect to the control point«

To determine the center of impact from the four bullet holes (fig. 89):

1. Connect any two bullet holes with a straight line and find the center of the distance between thee«

2. Connect the points thus obtained with the third hole, and divide the distance between them into three equal parts.

3. Connect the point of division closest to the two first holes with the fourth hole, and divide the distance between them into four equal parts. The point which is located three divisions from the fourth hole is the center of impact.

If the bullet holes are located symmetrically, the center of impact may be determined by one of the following two methods:

1. Connect the bullet holes located closest together; the centers of both straight lines are to be connected with the third line, and the line thus obtained is to be divided in half; the dividing point is the center of impact.

2t The bullet holes are connected with intersecting straight lines; the intersection of these lines is the center of impact.

If one of the holes is loceted a large distance from the remaining holes, it is not considered, and the center of impact is determined from the three holes.

In this method, two holes are connected bv a straight line, the center of this line is connected with the third hole, and the new line is divided into three equal parts; Ate 'point located two divisions from the third hole is the center .pf Impact. *

The center of impact should coincide with the control point or deviate from it do more than 5 cm in any direction«

If the center of Impact deviates more than S cm from the control point, the armorer-artificer adjusts the rifle by moving the front sight to the right or left or up aad down, depending upon the direction io which the center of impact deviates«

It must be borne in mind that the front sight must be moved in the direction in which the center of impact deviates.

If the center of impact deviates to the left of the control point, the front sight must be moved to the left; if deviation is up, the front sight must also be moved up (using screw-driver)-

The amount of displacement of the front sight is determined by multiplying the amount of deviation of the center of impact from the control point as measured on the target by the correction factor»

The correction factor for the AI automatic rifle with given conditions (range to target 100 m, range setting 3, length of sighting line 378 mm) is 0,0378.

EXAMPLES:

1. The center of impact deviates from the control point to the right by 12 cm, and 10 cm low.

In order for the center of impact to coincide with the control point, the front sight must be moved to the right 0.037ft times 12 equals 0.4S36 mm, is approximately equal to 0.5 mm, and low by 0.0378 times 10 equals 0.378 mm, is approximately equal to 0.4 mm.

2. The center of impact deviates from the control point to the left 19 cm and IS cm up. The front sight must be moved to the left 0,037S times 19 equals 0.7102 approximately equal to 0,7 mm, and Up 0.0378 times 15 equals 0*5670 mm, approximately equal to 0,6 mm.

NOTE: The amount of deviation of center of impact in cm is mulitiplied by the correction factor and the result is obtained in mm.

After the position of the front sight is corrected, the rifle is checked for accuracy once sore.

Moving the front sight laterally one millimeter displaces the center of impact by 26 cm at a range of 100 ei; screwing in (screwing out) the front sight the amount of one turn raises (lowers) the center of impact 20 cm. Hhe« the rifle is adjusted, a new graduation line is entered on the front sight slide and the old graduation line is obliterated.

It is forbidden to obliterate graduation lines in the base of the front sight.

.After the rifle is adjusted, the results and time of accuracy check are entered into the gun data card of the rifle (see Appendix 11).

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