M45 shotgun

The M45 TS Close Assault Weapon System is a shotgun used by the United Nations Space Command.

Design Details
Much like any other shotgun, the M45 TS is a special-purpose weapon used in any situation where the range of engagement is limited, over-penetration is not desirable, but maximum stopping power is required.

Trivia

 * The M45 TS will presumably be more powerful than the M90 Close Assault Weapon System in Halo 3 since Bungie has stated in a Game Informer interview that the rounds will now be packed closer when fired and the range has been improved as well, although this will make it harder to hit more than one enemy at close range. The ammo capacity from the Halo 3 version has been kept.
 * When the weapon's slide is locked to the rear, the loading port opens with it. Also, the shell is ejected from the same location it is inserted, the top.
 * It is possible the 'TS' in the name stands for Tactical Shotgun, making the official designation of the weapon the M45 Tactical Shotgun.