The energy of the .40 S&W exceeds all standard-pressure and +P 9x19mm Parabellum loadings and many standard-pressure .45 ACP rounds, generating between 450 and 600 foot-pounds (550 J and 800 J) of energy, depending on bullet weight, with mid to high 500 foot-pounds typical. Both the .40 S&W and the 9 mm Parabellum operate at a 35,000 psi (240 MPa) SAAMI maximum, compared to a 21,000 psi (150 MPa) maximum for .45 ACP. Go with the 40.