MIL-T-45379D(AT)
4.6.4.9.7.2 Azimuth indicator backlash. To determine conformance to 3.5.9.7.2, the turret shall be traversed in a CW direction without overtravel and the zero of the outer movable dial positioned in line with the 1 mil pointer. A fixed vertical reference line shall be observed through the gunner's telescope and the corresponding boresight knob position noted. The turret shall then be traversed CW approximately 50 mils and returned to its zero azimuth indicator position without overtravel. The movement of the gunner's telescope boresight deflection knob required to realine the vertical line of sight with its original reference line is backlash error and shall not exceed 0.5 mil.
4.6.4.9.7.3 Leveling devices. To determine conformance to 3.5.9.7.3, the main gun shall be leveled at zero elevation as indicated by a bore leveling gage position in the chamber. The leveling device on the ballistic drive shall be observed for accuracy.
4.6.4.9.8 Cupola weapon sighting system.
4.6.4.9.8.1 Synchronization. To determine conformance to 3.5.9.8.1, synchronization tests shall be conducted in accordance with the following procedure.
a. A telescope adaptor shall be inserted into the machine gun opening. b. A synchronization fixture shall be attached to the telescope adaptor.
c. A beam splitter and adaptor shall be attached to the periscope eyepiece.
d. Approximate zero gun position shall be established, laying from low to high.
e. The boresight knobs of the periscope shall be adjusted to autocollimate the periscope on the mirror of the synchronization fixture and the boresight knob position shall be recorded.
f. Laying from low to high, the periscope shall be within the synchronization limits specified in 3.5.9.8.1.
NOTE: Synchronization error at any gun position shall be measured by noting the boresight knob movement necessary to superimpose the periscope reticle on its reflected image from the mirror of the synchronization fixture.
4.6.4.9.8.2 Elevation backlash. To determine conformance to 3.5.9.8.2, backlash shall be checked after determining that synchronization requirements have been met. The equipment specified for synchronization checks of 4.6.4.9.8.1 shall be used for testing as follows:
a. Approximate zero gun position shall be established, laying from low to high.
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