Manual

15
2.4. Zeroing of rifle and procedure of optical sight operation
2.4.1. The sniper rifle being in the service of a subunit should be
zeroed. The necessity of rifle zeroing is determined by test firing.
Rifles are subjected to test firing:
a) on reception of the rifle by the subunit;
b) after the rifle parts repair or replacement, which may affect the
rifle fire accuracy;
c) in case of excessive deviation of the mean point of impact (MPI),
or bullet dispersion, which does not meet the accuracy
requirements. Under combat conditions the rifle accuracy should
be tested periodically whenever the situation permits.
2.4.2. The sniper rifle is test-fired by four shots, aiming thoroughly
and uniformly with the aid of the open sight. Fire is conducted at the
black rectangle, 20 cm wide and 30 cm high, secured on a white board, 1
m high and 0.5 m wide. The point of aim is the middle of the black
rectangle bottom edge. During firing when the open sight is used the
normal position of the MPI is marked with chalk or a colored pencil by
the plumb line, 16 cm above the point of aim. This point serves as the
check point (CP).
The range is 100 m; the sight is set at 3. Firing is conducted from
the prone position with support. To test-fire and zero a rifle, use
should be made of cartridges with ordinary bullets having a steel core.
Fire is conducted with knife bayonet removed. Upon firing the shots,
examine the target and arrangement of hits; determine accuracy of fire
and position of the MPI. The sniper rifle fire accuracy is considered
normal, if all the four hits are arranged within the circle, 8 mm in
diameter.
If the shot group does not meet the requirements, test firing is
repeated.
If the second test results are unsatisfactory, the sniper rifle
should be sent to the repair shop.
If the shot group is found normal, determine the MPI and its
position relative to the check point.
Determination of the mean point of impact is shown in Fig. 12. The
sniper rifle fire accuracy is considered normal, if the mean point of
impact coincides with the check point or deviates from it in any
direction by no more than 5 cm.
2.4.3. If during test-firing the MPI deviates by more than 5 cm from
the CP in any direction, the position of the front sight (as to its
height) or that of its body (as to side position) should be changed
accordingly. If the mean point of impact is below the check point, the
front sight should be screwed in, if it is above the check point, the
front sight should be screwed out.
If the MPI is to the left of the CP, the front sight body should be
shifted to the left, if to the right, shift the body to the right. The
front sight body displacement by 1 mm to the side and one complete
revolution of the front sight (when screwed in or out) will change the
position of the mean point of impact by 16 cm when fire is delivered at
a range of 100 m.