The M90 Close Assault Weapon System[2][3][4] (M90 CAWS) is one of many Allied primary shotguns and is one of the most effective close range infantry weapons used by front line forces. The M90 Shotgun is a pump-action, magazine-fed, dual tubular non-detachable type weapon designed from the M45E Tactical Shotgun.[5] The Weapon System Technologies DTM series shotgun is the most common shotgun employed by Allied Special Forces, law enforcement agencies, and sportsmen. The M90 has been in service for over 27 years and its design has changed very little. The M90’s immense power, ease of use, and reduced capacity for puncturing the hulls of spacecraft over many other UNSC weapon systems with standard 0000 (.38 cal pellets) ammunition are greatly appreciated. The M90 is often employed in urban conditions where the tight spaces are conducive to the shotgun's wide spray for defensive purposes and CQC. The military issued DTM series comes standard with an adjustable stock and pistol grip, although there are different models like the WST DTM/LE model which has a solid stock and no pistol grip. The DTM series of shotguns are available in 20-gauge and 10-gauge for the civilian market. The 8-gauge is only sold to law enforcement and military agencies.

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