Many cops unload their duty guns at shift's end and insert the cartridge from the chamber into the top of the magazine. Chambering the same cartridge day after day can cause the bullet to set-back in the case. With the .40 S&W this had the potential of doubling chamber pressures. When an officer reported for qualification and fired his duty ammo, the first shot—which was the cartridge with the bullet set back—could be very exciting. These problems have since been addressed with stronger cases and a more robust bullet crimp. Still, it's not a bad idea to cycle any cartridge you unload from the chamber of your handgun to the bottom of the magazine.