Editing M990 electrothermal-chemical smoothbore cannon

{{Status|Canon}}
{{Weapon infobox
|name=M990 electrothermal-chemical smoothbore cannon
|image=[[File:H5G-M820boom.png|300px]]
|manufacturer=[[Chalybs Defense Solutions]]
|series=
|type=Smoothbore tank gun{{Ref/Reuse|Universe}}
|cost=
|variant=
|service=[[Post-Covenant War conflicts]]
*[[2557]]-present{{Ref/Reuse|Universe}}
|length=
|width=
|height=
|weight=
|ammotype=150mm shells {{C|various}}{{Ref/Reuse|Universe}}{{Ref/Reuse|Enc22}}
|capacity=
|feed=
|operation=[[Wikipedia:Electrothermal-chemical technology|Electrothermal-chemical]]
|rate=
|velocity=
|optics=
|range=
}}
The '''M990 electrothermal-chemical smoothbore cannon''' is a vehicle-mounted heavy weapon in the service the primary armament of the [[M820 Scorpion]], introduced into widespread service in [[2557]].{{Ref/Site|Id=Universe|URL=https://www.halowaypoint.com/en-us/universe/vehicles/scorpion|Site=Halo Waypoint|Page=Scorpion|D=21|M=04|Y=2021}}{{Ref/Book|Id=Enc22|Enc22|Page=140}}

==Overview==
===Design details===
Unlike the [[M512 smooth-bore high-velocity cannon|M512 cannon]] mounted on the M808, or even the [[M310 smooth-bore high-velocity cannon|M310 cannons]] mounted on the [[M850 Grizzly]], the M990 is an [[Wikipedia:Electrothermal-chemical technology|electrothermal-chemical gun]], and is considered the single-biggest improvement on the M820 platform over its M808 predecessors.{{Ref/Reuse|Enc22}}

According with its new operating principle, the M990 breaks legacy munitions compatibility with its predecessor models and fires a much larger 150mm shell, and is capable of firing guided munitions and projected future advances in energetic propellants.{{Ref/Reuse|Universe}} Some of the projected propellant advances are already in service among the fleet of [[ONI Scorpion|select Scorpion variants]] operated by the [[Office of Naval Intelligence]]'s [[ONI Security|security forces]], which use an experimental shell and the latest energetic propellants.{{Ref/Game|H5G|List of REQ cards|REQ Card|Detail=ONI Scorpion Description|Quote=ONI spares no expense with its "security" Scorpions, outfitting them with experimental ammunition using the latest energetic propellants. Advanced Scorpion with heavy armor and upgraded cannon.}}{{Ref/Site|URL=https://www.halowaypoint.com/en-us/news/canon-fodder-a-time-to-give-tanks|Site=Halo Waypoint|Page=Canon Fodder - A Time to Give Tanks|D=14|M=07|Y=2021}}

The [[XM820B4 Scorpion]], an experimental model produced by [[Hannibal Weapon Systems]], uses the M990 ETC gun's hull and structure as a base for the integration of a fast-discharge [[laser]] weapon system. Aesthetically, this weapon has few outward differences than the standard M990, though is functionally a [[directed energy weapon]] rather than a conventional tank gun.{{Ref/Game|H5G|List of REQ cards|REQ Card|Detail=Hannibal Scorpion Description|Quote=This is but one of Hannibal Weapon Systems' tank test beds fitted with the latest in vehicle-borne directed energy weapons. Advanced Scorpion with heavy armor and fast-discharge laser currently undergoing trials within UNSC Infinity War Games.}}{{Ref/Site|Id=CFClose|URL=https://www.halowaypoint.com/en-us/news/canon-fodder-close-quarters|Site=Halo Waypoint|Page=Canon Fodder - Close Quarters|D=17|M=10|Y=2021}}

The M990 is extremely effective at penetrating heavy armor, including [[Type-58 Wraith]] tanks, and even Forerunner weapons such as the [[Z-510 focus turret]]. It is less effective against nimble aerial targets, such as the {{Pattern|D'nomlhe|Banshee}} or the [[Phaeton]], but is still easily capable of penetrating their armor.

==Gallery==
<gallery>
File:H5G M820Scorpion Turret Concept.jpg|Concept art of the Scorpion's turret.
</gallery>

==List of appearances==
*''[[Halo 5: Guardians]]'' {{1st}}

==Sources==
{{Ref/Sources}}

{{UNSC heavy weapons}}
[[Category:UNSC ground weapons]]
[[Category:Projectile weapons]]