shall be used for fire control and cannon bore alignment.
target shall be placed at the specified distance in a plane
perpendicular to the cannon bore.
The vertical line on the target
shall be set plumb with the plumb line established for cannon tube
The horizontal target line shall be established by
the zero elevation setting of the cannon tube which will establish
the required height of the target from the ground.
The borescope used for cannon tube elevation plumb travel
shall have a cross hair reticle mounted in a self-aligning
adapter to be inserted into the breech of the cannon so that the
reticle has a focusing range of five meters to infinity.
reticle of the telescope shall be collimated with respect to the
outside diameter of the adapter within 0.1 mil.
shall have a magnification of four or greater.
Peep sights having a aperture of 1/16 inch may be used
to eliminate parallax in the panaramic telescope and elbow
telescope, as necessary.
The carriage trunion shall be cross-leveled as a prepara-
tory step for cannon tube plumb travel.
Use cannon tube leveling pads for zeroing out cannon tube.
Only a calibrated gunner's quadrant shall be used as an inspection
aid on cannon tube pads.'
Sight through the borescope and align the Target line A
and B (Figure I) in coincidence with the borescope reticle lines.
Set the level vials on the mount M171 and quadrant M17
to the level position (bubbles centered) .
Sight through the panoramic telescope and align the
reticle to the intersecting target lines C and D (Figure I) with
the elevation and azimuth knobs. Ascertain that the level vial
bubbles for pitch and cross-level are centered and the azimuth
counter reads 3200.
Set the reticle of the telescope M138 to the zero position
and align to the target intersecting lines E and F (Figure I).
For reticle/target line coincidence, make all adjustments with
the boresight screws on the M172 mount.
1. The quadrant M18 level vial bubble shall be centered with
the elevation reading at 0000.
The cross-level vial bubble shall
be centered when boresight adjustments are set.