Armalite MG UNSC
From Halopedia, the Halo wiki
Armalite MG UNSC is a weapons manufacturer that, according to early concept art for Halo: Reach, produced the M392 Designated Marksman Rifle. However, all references to the organization were removed from the final game, likely because it shared it name with Armalite Inc., a real-world firearms manufacturer. It is possible that they were intended to be the same company. Canonically, the M392 is manufactured by Misriah Armory.