MIL-DTL-48557B
with appropriately labeled azimuth scale for the distance it is placed from the objective end
of the sighting device and place the vertical line of the wall target in coincidence with the
vertical reticle line of the sighting device and ensure that it is plumb. Using the test fixture,
create a cant angle of 88.9 mils as indicated on the fixture. Then cant the mount an equal
amount in the opposite direction until the mount s cant level bubble is centered. Elevate
the fixture to 300 mils elevation as read by the inspection aid on the cross-leveled
inspection aide support assembly. The actual fixture elevation will be 301.18, as read on
the scales of the fixture. Table VII can be referenced for the actual elevation readings of
the fixture. Set the elevation level vial bubble to the level position using the pitch
adjustment. Adjust the sighting device to the 27.0 mils azimuth correction setting and
observe that the position of the vertical line of the sighting device reticle is in coincidence
with the vertical line of the wall target within the tolerance specified in 3.7.11. The
azimuth correction test shall be performed in the left and right direction as specified in
3.7.11. The above procedure shall be performed at each of the elevation settings and
applicable cant angles in accordance with Table VII. Azimuth corrections at each elevation
and cant angle shall be within the tolerances specified in 3.7.11.
TABLE VII. Azimuth correction test fixture elevations.
Reference elevation
Cant angle (mils)
Actual fixture
(mils)
elevation (mils)
300
88.9
301.18
600
88.9
602.60
900
88.9
904.76
1200
88.9
1209.50
300
177.8
304.77
600
177.8
610.54
1100
177.8
1130.25
4.8 Level vial illumination. With fresh batteries installed, the mount shall be placed
in a room having a controlled light source. With the room completely dark and after the
tester has become dark adapted, the lights within the mount shall be switched on and the
level vial bubbles and graduation lines shall be observed for conformance to 3.8 while the
lights are slowly brought up to full brightness.
4.9 Knob torque. Use a standard torque measuring device with adapter 11747949
or equivalent to test the running torque of the pitch and cross level adjustment knobs for
conformance to 3.9. Each knob shall be rotated a minimum of 3 turns in each direction.
4.10 Interchangeability.
4.10.1 Interchangeability of mounting surface of M171A1 mount.
Interchangeability shall be verified by the insertion, seating, securing, and subsequent
removal of maximum interchangeability gage, 11747840, on the mounting surface of the
M171A1 mount.
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