MIL-STD-1258(WC)
30 June 1972
5. DETAIL REQUIREMENTS
5.1 Normal visual inspection. The interior surfaces of the barrel
shall be examined by normal visual inspection to determine the presence
of workmanship type defects. An acceptable chromium plated barrel will
show no evidence of darkened areas on the top of the lands or on the
grooves which are indicative of workmanship type defects on the interior
surfaces.
5.2 Visual COmpariSOn standards. The visual comparison standards
contained in figure .1 represents bore surface conditions for an acceptable
5.56mm, 7.62mm, and Cal .30 barrel (see 4.3, 4.4 and 5.1).
5.2.1 Figures 2 through 20 represent unacceptable types of bore
surface conditions in 5.56mm, 7.62mm, and Cal .30 barrels.
5.2.1.1 Figures 2 and 3 represent a nonmetallic inclusion discerned
by normal visual inspection as a darkened line on the surface of the
chromium plate. In these illustrations, a void caused by removal of some
nonmetallic material by electropolishing remains evident after chromium
plating. The direction of an inclusion type of defect is parallel to the
centerline of the barrel and does not follow the twist of the rifling.
This directional pattern is not clearly evident in the illuminations
because of the limited field of view obtained through the borescope.
5.2.1.2 Figure 4 represents a nonmetallic inclusion over which a
series of small nodules of chromium has formed.
5.2.1.3 Figures 5 and 6 represent plated over tool marks.
5.2.1.4 Figure 7 represents a severe gouge caused by a broken tool.
5.2.1.5 Figures 8 and 9 represent torn land and groove.
5.2.1.6
Figure 10 represents a rough land and rough groove adjacent
Nodules have formed on the rough surfaces. The smeared
to the land.
metal effect
is the result of material being removed from the projectile
by the rough
deposits during proof firing test.
5.2.1.7 Figures 11, 12 and 13 represent various degrees of rough
deposit. The darkened areas in figures 12 and 13 are copper deposits
caused by the projectile during proof firing.
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