The XO-16 Chaingun is a fast firing, belt fed, fully automatic Titan weapon. Possessing a considerable rate of fire coupled with high precision and low recoil, very rarely will a Titan pilot miss its intended target. This versatility makes it an ideal weapon for mid to long range engagements, while at close range hailing an opponent with enough high calibre rounds will cause other Titan opponents slight vision-optics distortion, disorientation and confusion. A perfect two way weapon, effective against both Pilots and Titans, it is the go-to weapon for all Pilots of any level.
Perhaps its only drawback is - especially with the Accelerator - its relative inefficiency. The XO-16 can burn through its ammo reserve with the same kind of speed that it chews up enemy Titans. Pilots adept at keeping their Titan combat-capable may ultimately find themselves running out of ammo during prolonged engagements, especially during Frontier Defense.
Effective in most situations against all opponents, the XO-16 is best used on open maps with clear lines of sight. Its instantaneous projectile and fast, sustained rate of fire make in perfect for wearing Titans down. It can easily cut down pilots, and is much more effective at cutting down fast moving and ejecting Pilots than any other weapon in its class. Its main drawbacks include its lack of overall power-per shot, as other Titan weapons do much more damage per shot in a shorter time span. Any Titan-class works well with the XO-16, an Ogre can withstand more punishment, which can make up for this weapons lack of firepower. The Stryder can be used to cover long distances, keeping out of direct conflict with its mobility, while dealing sustained firepower against enemies. The Atlas's versatility can be combined with this weapons, making an overall solid class with no significant strengths or weaknesses, while receiving the added boost of this Titans Damage Core ability.
According to Ryan Lastimosa, Senior Artist at Respawn Entertainment, who designed many of the weapons, the XO-16, "is based on a lot of things. It’s based off of a 20mm anti-aircraft cannon with some inspiration from the CIWS". And, as a reference to Robotech, it has big "No Step" decals.
Originally the XOTBR-16 was designed to be converted into a field gun when not used by a Titan, but that feature was cut.
The XOTBR-16 bears a resemblance to the M60 Machine Gun used by the Avatars in James Cameron's Avatar.
Information about the weapon's ammunition is inconsistent. The drum magazine reads 30mm cartriges, but the spent cartridges say 20mm; this latter figure is backed by Ryan Lastimosa. The XO16A2 Chaingun in Titanfall 2 supports this 20mm round with its description. It is also described as firing 1.6 inch slugs, but this is also wrong. By estimating it's size compared to the 40mm Canon, it appears to fire ~35mm rounds. This coupled with the fact that a 20mm round would fail to damage as much armor as a Titan's makes it look like the most logical size.
The letters BMFG appears on the magazine of the weapon. This might be a reference to the BFG (Short for Big Fucking Gun) from the Doom series. BMFG likely stands for Big Mother Fucking Gun. It is likely a reference, however, to the company that manufactures the weapon; Brockhaurd Manufacturing.
An XOTBR-16 can be seen wielded by a Scorch in Titanfall 2 opening cutscene.
Image of the XO-16, before being ejected from Titan
Another series of renders
Concept Art depicting the originally planned deployable stand for the weapon