The Shorty-Forty is based on the 6900/4013tsw frame size. It is a double stack and will accept the full size 4000 series 11rd mags that will hang out a little. They make a adaptor that fills out the grip when used in these guns. The CS40 is just a tad shorter in length but with the Hogue grips is about the same thickness in the grip as the Shorty. Either would make a good carry gun, but the Shorty retailed for twice the price of the CS.