The Colt 6504 9mm autoloader is a good weapon to use when you get it. It allows you to take ranged shots, which can be pretty helpful if your action points are low. However, due to the nature of the battle engine, remember to move your character away from the target, or else he'll keep on firing without moving.
Unused models and icons in the tech demo's files indicate that it could be modified with an extended magazine, a silencer, or both.
Found on a female Communist Insurgent that's in the red building on the west side of main street, in the Van Buren tech demo.
While the modified variants don't appear in the Van Buren tech demo, they are still present in the game files and can be spawned with the following console commands, but they remain as non-functional weapons.