The sidearm typically issued to law enforcement personnel in the United States is frequently a semi-automatic pistol chambered in 9mm, .40 S&W, or .45 ACP. For example, many agencies have adopted models from manufacturers such as Glock, SIG Sauer, and Smith & Wesson.
The selection of a specific firearm for police use involves considerations of reliability, accuracy, stopping power, ease of use, and departmental policy. The duty weapon provides a critical means of defense and response to potential threats encountered while on patrol and during emergency situations. Historically, revolvers were the standard, but semi-automatic pistols offer increased capacity and faster reloading capabilities, leading to their widespread adoption.