M392 DMR

"The single-shot DMR fits somewhere between the sniper rifle and the battle rifle. It's deadly at range, but a quick trigger finger and careful aim assure that even at medium to short distances it packs a punch."

- Game Informer

The M392 Designated Marksman Rifle, commonly abbreviated as the DMR, is a combat rifle used by the United Nations Space Command.

Background
Although it saw more widespread use throughout all branches of the UNSC prior to 2548, it has since been superseded in use by the BR55 in all branches but the UNSC Army.

Design Details
The M392 Designated Marksman Rifle is an air-cooled, gas-operated select-fire bullpup rifle that fires 7.62x51mm ammunition. It is mounted with a scope capable of 3x zoom and possess a fire selector switch located above the grip of the weapon, and a magazine release button, which is located directly above the magazine housing, behind the trigger.

Trivia

 * Stamped on the comb of the rifle are the words ARMALITE MG UNSC. This is possibly the manufacturer or a reference to real-world manufacturer ArmaLite Corp.
 * The designation of this rifle model as a "Designated Marksman Rifle" would seem to indicate that it was designed for use in squad-based combat, and not as a dedicated sniping tool. Designated Marksmen function in U.S. military fire teams to provide long-range support to their teams. This contrasts with Snipers who operate in small sniper-based squads and received more specialized training.
 * Designated Marksman is a military marksman role in United States Military infantry squads, intended to provide accurate fire on a squad-level, rather than with a separate "dedicated sniper" unit.
 * This weapon had technically appeared "first" in the Halo 2 demo, that Bungie premiered, as the original Battle Rifle. At that time in Halo 2's development, the BR55 Battle Rifle was yet to be a burst fire weapon and was much more along the lines of the DMR. It appeared to do much more comparable damage to the DMR and lacked the visible refinement the current BR55 Battle Rifle or BR55HB SR Battle Rifle had and most notably, fired single shots.
 * This weapon is aesthetically and functionally similar to the Kel-Tec RFB, in that both weapons use the 7.62x51mm NATO round, sport the bullpup configuration, and fire in semi-automatic mode.