Pvt. Paduk claimed that Kilo Squad subdued armored enemies using only shotguns.
USE GNASHERS AND SAWED-OFF SHOTGUNS ONLY
Near the very end of the level, you will run up a few short sets of stairs. Look for the COG tag at the top of the short stairs; there's a slightly longer set of stairs near the COG tag that has an Onyx ammo case.