Caution: The front band must be assembled on the barrel before the front sight is assembled.
Place front sight key in keyway in top of barrel at muzzle with pin notch facing up. Tap key snugly toward front end of keyway and stake metal of sight over both ends of pin to hold it in position. Slide front sight on barrel with sloping faces of wings to rear. Using front sight assembling tool 716313 mate keyway and key in barrel (Fig. 64) and drive sight on barrel (Fig. 65) until pinhole in sights is in alignment with pin notch in key. Install front sight pin and stake metal of sight over both ends of pin to hold it in position.
Drive sight forward and stake barrel against rear end of key.
Note. If practicable, the front sight will be kept mated with the barrel and receiver assembly from which it was removed.
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.
a. 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 disassembling. 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 worn 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.
MWCi 32« Wi ttPiA« rvrt REAR SIGHTS
Figure 66. L-type (leaf type) rear sight assembly.
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
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.
f. 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:
(1) The right-hand side of the sight base should not be pushed to the left beyond the point where it is flush with the side of the dovetail on the receiver.
(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.
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