SECTION Vm. REAR SIGHT ASSEMBLY
GENERAL
Carbines of early manufacture were equipped
with an "L" type (leaf type) rear sight (Fig. 66)
composed of two integral leaves set at right angles
to each other. By Modification Work Order ORD
B28-W3 this sight is replaced by the adjustable rear
sight. All. carbines of later manufacture are e-
quipped with adjustable rear sight 6573955 or
7160060 (Fig. 67), which differ only in method of
manufacture. Sight 6573955 is a machined type,
and sight 7160060 is a stamped type. The function
and operation of both sights are identical.
DISASSEMBLY (FIELD MAINTENANCE)
a. Scribe a mark on the receiver directly
opposite line on sight base for sight assembly
6573955 (machined type) and in the receiver
directly opposite mark on zero sight plate for
sight assembly 7160060 (stamped type). This is
necessary for proper alignment in assembly.
b. Place adjustable rear sight assembling
tool 7312068 on the receiver with the lip of the
tool riding on the operating slide guideway in the
receiver. If the sight is of the stamped type, insert
spacer (Fig. 69) (hanging at end of chain on tool)
in place to prevent distortion of sight base wings.
With the right hand jack screw retracted to the
extreme position and out of the way, slide the tool
over the sight (Fig. 68).
c. Push guide of tool (sliding member to
which chain is attached), so that inside end rests on
side wing of sight base, fit recess of connector over
outside end of guide and tighten left hand jack
screw. As pressure is applied, tap connector with a
brass hammer and take up slack with jack screw
until sight is removed.
INSPECTION
o. Check sight base for looseness and sides of
base will not be bent or distorted; damage of this
nature may be caused by assembling and disas-
sembling. Check ramp for worn or burred guide-
ways and index ball retention notches on the floor
of the sight ramp .
b. Check windage screw for wear of threads,
burrs, security and staking, and check windage
screw knob for wom knurling. The windage knob
must be free enough for hand operation, move
with distinct clicks, and retain its setting. It should
be possible to move the ramp to extreme limit on
either side without objectionable binding. With
ramp centered in sight base, press windage knob
to left and release to test spring action of index
ball on knob. There should be merely lateral
movement of the knob due to pressure and index
spring action. When released, there should be
clearance between inner face of knob and sight
base.
c. With ramp centered in sight base, attempt
to move lower end of ramp from side to side.
Figure 66. L-type (leaf type) rear sight assembly
There should be practically no lateral movement.
If movement is present, it indicates worn threads
on either windage screw, ramp, or both. Press
rear end of ramp down and release to check spring
action of ramp guide plunger.
d, Move aperture slide up and down full
length of ramp. Slide should move freely but with
distinct clicks and be positively retained at each
sight setting. The slide should be stopped at the
front (lower) end of the ramp and at the rear
(top). There should be no undue looseness of the
aperture slide in the ramp guideways. Inspect peep
hole for absence of shine and foreign matter.
' e. On the stamped type sight, the index plate
should be so positioned that the index line is
in the approximate center of the base. (In other
words, the index plate must not be rotated to one...
Figure 67. Adjustable rear sight assembly for
M1.
M1A1
and M2 carbines.
Figure 68. Removing adjustable rear sight.
....side or the other on its pivot because the full
range of adjustment of the plate is intended for
the user of the weapon.) The rivet should be tight
enough to retain the plate firmly in its set position.
/ On the machined type sight, the index
plate should be positioned approximately in the
center of the ramp and the screw must be tight
enough to retain the plate firmly in that position.
g. After targeting (DEPOT MAINTENANCE
ONLY) and adjustment of the rear sight on the
receiver, check to assure that the overhang of the
rear sight base does not exceed the following
limits: m
(1) The right-hand side of the sight base
should not be pushed to the left be-
yond the point where it is flush with
the side of the dovetail on the re-
ceiver.
(2) The sight should be pushed onto the
receiver far enough so that the left-
hand side of the base is flush or beyond
the left-hand side of the dovetail on
the receiver.
h. After targeting, check to assure that the
receiver is staked to retain the rear sight firmly
in place.
REPAIR AND REBUILD
o. Repair. As the adjustable rear sight is
replaceable only as an assembly, no replacement
spare parts are furnished for field repair. Check
machined type sight for loose or missing index
plate and screw. The sight should be kept clean and
lightly oiled to prevent rusting and insure proper
operation.
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