This answer to this question is as varied as the number of law enforcement agencies that exist across this great nation. There are some commonalities and some vast differences regarding which firearms and ammo police use on duty.

Duty Pistol Calibers

After a major shift initiated by the FBI just a few years ago, the 9mm reigns supreme as the standard duty caliber in issue handguns across the U.S., despite the fact that, almost 30 years ago, the same FBI pushed the development of the .40 Smith & Wesson cartridge as the ultimate law enforcement round. The .40 replaced the 10mm as the FBI’s ultimate cartridge and also sounded the death knell for the .38 Special revolver, which had been the standard since the 1900s.

The 9mm is a reasonable choice as a duty round. The 9mm is reasonably powerful and accurate and is more mild-mannered than the .40. But what about the specific duty pistols and the ammunition that stokes them? Well, that’s the complicated part.

Duty Handguns: How Are They Chosen?

Law enforcement agencies go about their weapon selection in one of two ways: Either the agency mandates an issue handgun or the officers choose. I have worked for both agencies that issue and agencies that allow, or even require, each officer to purchase his or her duty gun.

Police-Department-Issued Firearms

In agencies that issue duty handguns to their officers, Glock holds about 67 percent of the market across the U.S. It was up near 72 percent at one time, but the S&W M&P has made significant inroads. This was followed by SIG Sauer, which got a big boost by the military adoption of the P320 as the M17. The Ohio State Patrol, in fact, just switched from SIG P226 to SIG P320.

When agencies choose a duty pistol, they try to select what is best for their troops, but several factors come into play. The biggest is cost; which manufacturer is going to give the agency the most bang for its buck? The “very best” duty pistol may not be one the department can afford. For some extremely lucky agencies, cost of duty guns is not an issue. In the small, well-to-do village I live just outside of, for example, the duty pistol is the Les Baer .45.

Departments that issue ammo also select the brand and bullet type based on cost. In Ohio, there is a statewide bid/contract system for ammo that any agency can use for purchasing rounds. The most commonly encountered duty ammo is Winchester Ranger because it is priced best. This doesn’t mean Ranger is bad ammo. It is good ammo … but is not necessarily selected based on agency testing. With this system, it is hard for other companies who may have a superior product to compete in volume.

Individually Purchased

In agencies where officers are allowed personal duty and off-duty gun purchases, each LEO purchases whichever handgun suits him or her best. In these places, you will usually see Glocks, M&Ps, SIGs, Colts or Berettas. You will also see them in a variety of calibers: 9mm, .40, .45, .357 SIG, 10mm and maybe even a .38 Super. But while some departments will supply standard-caliber ammunition (9mm, .40, .45), they will not supply rounds such as .357 SIG or 10mm. As long as the ammo is an approved, controlled-expansion-type, the brand usually doesn’t matter.

What About Rifles and Shotguns?

Interestingly, many agencies that issue AR-15s for duty — especially those from the government 1033 program — also allow officers to carry their own personal ARs (usually customized M4s). Shotguns are rarely utilized for anything other than less-lethal round delivery and don’t factor in much anymore.

If you want to learn more about what pistols law enforcement officers prefer, find an agency that allows or requires the personal purchase of duty and off-duty handguns and rifles. The officers at these agencies tend to be more gun-savvy. If an officer in this type of agency isn’t busy, ask about his or her firearms. Most will be happy to talk about them. And never criticize their choices; just listen.