If you look back through the threads here, you will find several siting studies showing the 9MM doing just as much damage as a 45 ACP, if you use the right ammo. You're not going to "knock down" anyone with any handgun round anyway. As for the Springer 1911's, I have no first-hand knowledge of their accuracy. I would guess they are equally accurate in 9 or 45. There are some members here with both, so hopefully they will chime in.