The RE-45 Autopistol is a Pilot anti-personnel fully automatic machine pistol that appears in Titanfall and Titanfall 2. It serves as a reliable "spray-and-pray" backup sidearm for pilots at close range.
The RE-45 Autopistol is a .45 caliber pistol intended for use at close range. It loses damage and accuracy over long distances, so it is not as suitable for medium to long ranges as the Hammond P2011 or B3 Wingman. However, this weapon is best used when sneaking up on unsuspecting players with the use of Cloak, since it still retains maximum damage at close range; just make sure the victim doesn't turn around though.
Alternatively, it works well as a spray-and-pray backup gun.