HST's have changed the game a lot with their ability to expand. Considering the 40 S&W 180gr and the 45 ACP 230gr have about the same sectional density, and they both penetrate and expand almost exactly the same, is there any advantage with the 45 ACP. I am taking my pentration and expansion numbers from the ATK HST poster. I have both rounds and the 45 has significantly more recoil, requires a larger shooting platform and may hold less rounds. These are both low energy rounds, so that is not a factor. I am coming to the conclusion that the 40 180gr HST may be the better round.