The DC Single Action is a DLC weapon (from the Bounty Hunters DLC). The weapon can be dropped through a DLC weapon chests or purchased for 400 uncharted points.
The DC Single Action has high damage accuracy moderate recoil, and rate of fire. It's best used mid range.
The DC Single Action is likely based on the real life Colt Single Action Army, known as "The Gun That Won the West" and "The greatest handgun ever made".