The 40 Smith & Wesson won't blow you away with muzzle energy. Rounds like the Hornady Critical Defense 165 grain FTX have about 500 ft lbs of muzzle energy – the higher end of the spectrum in terms of muzzle energy you can reasonably expect from standard pressure factory ammo.

We can typically expect 40 Smith and Wesson muzzle energies to range between 250 and 600 ft lbs.

Feel free to check out a more in-depth look at all the 40 S&W Ballistics here: https://ammo.com/ballistics/40-sw-ballistics