Part of a news release from SIG:
SIG SAUER, Inc. is pleased to announce the United States Special Operation Command (USSOCOM), working closely with SIG SAUER, has completed a safety certification of the new SIG SAUER MG 338 Machine Gun, SIG SAUER 338 Norma Mag Ammunition, and Next Generation Suppressors. Following this historic official safety certification, SIG SAUER has completed deliveries of multiple systems, comprised of the MG 338 Machine Guns, 338 Norma Mag Ammunition, and Next Generation Suppressors – all researched, designed, engineered, and manufactured by SIG SAUER in the U.S.A."
More information here:
Screen shots showing SIG .338 NM ammunition in belts, from a YouTube video (video can be accessed via the above listed webpage):