I think it might be about 25% more than a 9MM - based on the increase in strength of the recoil spring going up to the .40. But they both kick - and neither is real bad. There are lots of female police officers who shoot and carry .40 caliber autos - have to qualify every quarter. You might consider staying away from the 135 and 155 grain full power factory loads - they feel a lot sharper and harsher than the 180 grain stuff. Also, Federal makes a factory round called "Personal Defense" that has pretty mild recoil. Good luck. Roskoe