Take the allen screw out of the back of the stock. That slides off to reveal the buffer tube. Remove the buffer and spring from the tube by pressing down on the buffer detent. The buffer tube can now be unscrewed from the receiver. Watch the plate that is held to the back of the receiver with the buffer tube though, as it holds in the safety selector detent and spring on the right side.
Installing the CAR stock will require a CAR wrench though.
