DESCRIPTION
This gun was inspired by the 40mm Tracker Cannon from Titanfall 2, scaled down to human size. I wanted to make a clunky, industrial sci-fi looking heavy weapon that had a reciprocating barrel like an artillery gun. I also took inspiration from modern military autocannons such as the 25mm M242 Bushmaster, however I decided to go with 20mm so as to plausibly maintain a respectable magazine capacity.

I started with the base game Light Machine Gun mesh and removed everything except for the buttstock, trigger and handguard. I then added the pistol grip from the Anti-Materiel Rifle, the barrel from the Grenade Machine Gun, the carry handle from the Missile Launcher, the receiver from the Sentry Turret, and the arm from the Sentry Bot. Lastly, I used the ammo dispenser from Operation: Anchorage as the drum magazine.

The weapon is chambered for a new custom ammo type - 20x102mm, also known as 20mm Vulcan. It's the cartridge that's been used as the principal cannon armament for U.S. military fixed-wing aircraft since maybe the 1960s. I've added four varieties for you to choose from:

• Target Practice (TP) - An inert training round that only does ballistic damage
• Armor Piercing Incendiary (API) - Better armor-penetrating capability with an incendiary effect
• High Explosive Incendiary (HEI) - Explodes on impact with an incendiary effect
• Semi-Armor Piercing High Explosive Incendiary (SAPHEI) - A jack-of-all-trades round that is armor-penetrating, explodes on impact and has an incendiary effect
  

Being a primarily military cartridge, it's not really something you can make using a typical civilian reloading bench. You can reliably acquire them from military airfield sources, although they'll be much rarer elsewhere.

Gameplay-wise, this weapon is fully-automatic, albeit with a slow enough rate of fire that you can easily take single shots if necessary. It can't be modded and must be repaired by a merchant or by using Weapon Repair Kits. I've also added the weapon to all the appropriate form lists, so that all perks and challenges that affect automatic rifles will work as expected.


LOCATION
The weapon and ammo can be purchased from the Gun Runners and other vendors across the Wasteland, or found in random loot drops. Of course, if you're feeling lazy, you can always use the following console command (Substitute ## with the Mod Index of the plugin in your load order):

player.AddItem ##000ADE 1;Gives 1 20mm AutoCannon
player.AddItem ##000ADF 50;Gives 50 20mm Target Practice rounds
player.AddItem ##000AE0 50;Gives 50 20mm Armor Piercing Incendiary rounds
player.AddItem ##000AE1 50;Gives 50 20mm High Explosive Incendiary rounds
player.AddItem ##000AE2 50;Gives 50 20mm Semi-Armor Piercing High Explosive Incendiary rounds

Detailed Instructions:

INSTALLATION
Extract all the files in the archive to your New Vegas data folder (which is the same folder where FalloutNV.esm is located) and then enable the ESP either in your mod manager of choice, or under "Data Files" in the launcher that runs when you start up New Vegas.