The following is the way to identify chromed barrels from unchromed barrels.

Stampings on the barrel approximately one inch rearward from the flash suppressor are as follows

(a) (SAK MP C) SAK is the manufacturer's stamp, MP indicates magnetic partical inspection, C indicates chrome chamber only, or (C MP C) C = Colt Manufacturer, MP = magnetic partical inspection, and C = chrome chamber only.

(b) Other markings which indicate chrome chamber only are "C" alone or "RUC" or "RNC" alone. A "C" stamped on the barrel between the rings of the front sight base also indicates chromed chamber only.

(c) Markings the same as in (a) above with the last letter "B" indicate a fully chromed bore and chamber.

(d) Other markings such as "CB" alone indicate a fully chromed chamber and bore.

(e) The latest configuration is identified with the words "Chrome Bore" written out.

(f) Barrel that does not meet the above criteria is non-chrome.

To insure proper operation of the gages, the barrel must be clean prior to performing the tests.

The following information pertains to the gages required for the upper receiver and barrel assembly.

(a) Barrel erosion gage, P/N 7799792, is to be used to check barrels that are not chromed. Instructions for its use are on the tag attached to the gage. The first line from the end of the gage is the reject line. The second line is no longer used.

(b) Barrel erosion gage, P/N 8448496, is to be used only on fully chromed barrels. Instructions for its use are on the tag attached to the gage.

(c) The muzzle erosion gage, P/N 8446677, is used on the unchromed barrel only. It is not required for use on chromed bore barrels. Instructions on its use are on the tag attached to the gage.

(d) The bore straightness gage, P/N 8448202, is required for use on all barrels. The gage must pass through the barrel without force.

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