Counter backlash may be eliminated by always making the
last movement in the elevation counter mechanism from high to
Backlash in the panoramic telescope M137 may be eliminated
by always approaching the target from left to right.
184.108.40.206 Gun elevation-plumb travel.-The howitzer shall be
cross leveled using mechanical jacks.
Using a borescope, track
a plumb line through a range of O to 978 mils (min.) elevation.
220.127.116.11 Alignment of mount M171, panoramic telescope M137
and quadrant M17
Set the cannon tube at zero elevation and center all
level vial bubbles.
The quadrant elevation level vial shall be adjusted as
necessary and shall meet the requirements of 18.104.22.168.a.
Subsequent to boresighting, the panoramic telescope shall
align on the M139 alignment device at 4800 mils within the
limits specified in 22.214.171.124.b.
Remove the alignment device before
elevating the gun.
d. The gun tube shall be elevated from zero to 1275 mils
in 200 mil increments.
The pitch and cross-level knobs shall
be rotated to relevel the mount and the level vial bubbles
Caution should be taken when rotating the knobs in
one direction so as not to introduce backlash.
should occur, repeat the procedure with the applicable knob. At
each 200 mil increment the level vials shall be centered and the
verticle line of the telescope's reticle shall not deviate more
than the limits specified in 126.96.36.199.c throughout the range of
zero to 899 mils.
Continue the above procedure starting at
900 mils to 1275 mils in 200 mil increments.
For the higher
elevations, deviation shall not exceed the limits specified in
188.8.131.52 Alignment of telescope M138, mount M172 and
The cannon tube shall be set at zero elevation.
a calibrated gunner's quadrant on the pads provided on the mount.
The elevation pads shall be parallel to the cannon tube within
the limits specified in 184.108.40.206.a.
Set the quadrant to read 0000.
The elevation level vial
bubble shall be centered within the limits specified in 220.127.116.11.b,
as measured with the calibrated gunner's quadrant.