a. Check sight to see that it is tight on the barrel and free from malformation and burrs, and to assure that the barrel has been staked at the rear end of the front sight keyway. In any staking at this point, caution must be exercised to avoid distortion of the base. It is required that the front sight be tapped forward on the barrel to take up any clearance between the key, keyway, pin, and sight, and that the metal of the barrel at the end of the keyway be upset against the key to secure the sight in this position.

b. Check to assure that staking of the front sight keyway and the application of the proof-mark have not distorted the bore.

c. Check to assure that the ring portion of the front band surrounds the barrel with spring tension.

d. Check crimping of front sight; it must be crimped at each end of the pinhole to prevent the pin from coming out.

e. Inspect wings; any deformation due to installation of sight on barrel or otherwise is cause for rejection.

f. Check height of blade; it must be not less than 0.140 inch, measured from the base of the blade. This is necessary for a good sight picture. In actual practice, it has been found necessary to maintain a height of approximately 0.315 inch in. order to target by bore sighting. Sights, not conforming to this 0.315-inch dimension, will be retained for reworking.

Figure 63. Removing front sight.
Figure 64. Aligning front sight.

g. The height of the blade is adjusted by depot maintenance so that the carbine will meet the targeting requirements defined on page 102. This is done by filing down the blade. The blade contains sufficient stock to adjust height during targeting.

h. Inspect the top of blade; it must be square and coated with Magic Blue (or similar substance) to prevent gloss and preserve the surface.

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