This page documents an R2D XBOX exclusive feature. Bear in mind, this wasn't around in the original R2D game.
Massacring the zombie race just got a hell of a lot easier with this. With the sharpest bullets that can be supplied, this does 200 damage towards zombies, insta-killing most and severely weakening a Tank. Be warned, the bullets come in limited supply and you are immobile while having this mount. This is, however, a small price to pay with this in your arsenal.
The XR500 has 220 ammo. Try not to waste any.
You cannot move this mount. Be wary of any hoards approaching.
You don't take damage while using this mount.
You can use the XR500 for a certain amount of time before despawning. There is also a cooldown to spawn it.
While it does 200 damage, it does not damage on bosses, such as King Cake.
The XR500 is the second mount to be added into R2D.
The XR500 can trip players if the mount is spawned near them.
The XR500 can glitch you inside buildings. This is bannable.
A picture containing the XR500 model was posted to PlaceRebuilder's twitter on March 11th 2016.