The SIG Sauer P320, designated the M17 (full-size) and M18 (carry-size) in US service, is a semi-automatic pistol produced by SIG Sauer since 2014.


The P320 was designed by Adrian Thomele, Thomas Metzger, Michael Mayerl and Ethan Lessard in 2014 and put into production the same year. The pistol was designed as a modular system from the ground up.

The P320 was SIG Sauer's submission for the XM17 Modular Handgun System competition; the P320 was declared the victor of the competition and was adopted as the M17; carry-sized models are designated the M18.[1][2]

The first users to receive the M17 was the 101st Airborne Division based in Fort Campbell, Kentucky; it was well-liked by the soldiers who tested it, with a lighter trigger and ease of use being main points of praise.[3] The P320 is currently being used by a variety of different countries, such as Denmark, Thailand and most notably, the United States.

The P320 was awarded American Rifleman's Handgun of the Year award in 2016.[4]

Design detailsEdit

A further development of the P250,[5] the P320 is a striker-fired short recoil-operated pistol designed to be a modular platform from the ground up. The heart of the P320 is a stainless steel "fire control unit", a set of parts consisting of an integrated fire control group, ambidextrous slide release, ejector, four rails and an ambidextrous safety. This one-piece fire control unit allows the system to remain modular as the gun is essentially built around it.[6]

The pistol is available in four calibers: 9×19mm Parabellum, .357 SIG, .40 S&W and .45 ACP. Pistols produced in the former three calibers have four barrel and slide sizes, along with four frame sizes marked as full, carry, compact and sub-compact; threaded barrels are also available.[4] With the use of caliber exchange kits, the calibers of the aforementioned variants can be changed back and forth; the same goes with the slides (i.e. a 9mm carry-sized gun can be changed to a 9mm full-sized gun).

The P320 uses glass-filled polymer grip frames; three grip sizes are available, namely small, medium and large. These grip sizes can be freely interchanged between the aforementioned four frame sizes. Parts on .45 ACP P320s may not be interchanged with parts from other P320s of lower calibers, although the .45 ACP P320s have their own varying grip sizes as well.[7]

The fire control unit is where the serial number of the gun is located; it is part of the one part that cannot be changed with regards to registration and is in effect the firearm regardless of whatever frame or grip is attached. The P320 can be field-stripped without the trigger being depressed, an additional safety feature meant to prevent negligent discharges from occurring;[6] by simply locking the action open with the holdopen lever, removing the magazine and removing the takedown pin, the slide can be slipped off the receiver.[8]

Similar to most other SIG Sauer pistols, the P320 uses what is colloquially known as the SIG Sauer System, a refinement of the short recoil action found on pistols such as the Mle 1935 pistol where the gun has a cam-operated barrel. The P320 has a variety of different sights, including SIGLITE sights, SIG Sauer's name for tritium-illuminated night sights and the ROMEO1 optical sight.

The P320s have a few different sub-variants, including the RX and X-Series; RX-Series P320s come equipped with the ROMEO1 slide-mounted sight as standard,[9] while X-Series P320s come equipped with the X Grip module, a squarer and flatter grip module when compared to normal P320 grips, giving it a slightly boxier feel but also assist in reducing muzzle flip.[10]


Many variants of the P320/M17 exist.

Standard production variants of the P320 are as follows:

Model Caliber State-compliant Magazine capacity Number of magazines Sights
Nitron Full 9mm CT/HI/NY 10 2 SIGLITE
Nitron Full 9mm 17 2 SIGLITE
Nitron Full .40 S&W CT/HI/NY 10 2 SIGLITE
Nitron Full .40 S&W 14 2 SIGLITE
Nitron Full .45 ACP CT/HI/NY 10 2 Contrast sights
Nitron Full .45 ACP 10 2 SIGLITE
Nitron Compact 9mm CT/HI/MO/NY 10 2 Contrast sights
Nitron Compact 9mm CT/HI/MO/NY 10 2 SIGLITE
Nitron Compact MS 9mm MA 10 2 SIGLITE
Nitron Compact 9mm 15 2 SIGLITE
Nitron Compact TB 9mm 15 2 SIGLITE
Nitron Compact MS 9mm 15 2 SIGLITE
Nitron Compact .40 S&W CT/HI/MO/NY 10 2 Contrast sights
Nitron Compact .40 S&W CT/HI/MO/NY 10 2 SIGLITE
Nitron Compact .40 S&W 13 2 SIGLITE
Nitron Compact .45 ACP 9 2 Contrast sights
Nitron Compact MS .45 ACP MA 9 2 SIGLITE
Nitron Compact MS .45 ACP 9 2 SIGLITE
Nitron Carry 9mm CT/HI/NY 10 2 SIGLITE
Nitron Carry 9mm 17 2 SIGLITE
Nitron Carry TB 9mm 10 2 SIGLITE
Nitron Carry 357 Sig CT/HI/NY 10 2 SIGLITE
Nitron Carry 9mm 14 2 SIGLITE
Nitron Carry .40 S&W CT/HI/NY 10 2 SIGLITE
Nitron SubCompact 9mm 12 2 SIGLITE
Nitron SubCompact .40 S&W 10 2 SIGLITE
FDE Carry .40 S&W 14 2 SIGLITE
FDE Compact 9mm 10 2 SIGLITE
FDE Compact 9mm 15 2 SIGLITE
FDE Compact .35 Sig 10 2 SIGLITE
FDE Compact .40 S&W 10 2 SIGLITE
Tacops Full 9mm 21 4 TFO front sight, SIGLITE rear sights
Tacops Carry TB 9mm 21 4 Tall SIGLITE
X-Five Full 9mm 5" Barrel 21 4 Dawson Precision Fiber Optic front and fully-adjustable rear sights
RX Full 9mm CT/HI/NY 10 2 SIGLITE
RX Full 9mm 17 2 SIGLITE
RX Compact 9mm CT/HI/NY 15 2 Tall SIGLITE
RX Compact 9mm CT/HI/NY 10 2 SIGLITE
RX Compact 9mm CT/HI/NY 15 2 SIGLITE
X-Carry 9mm Flat trigger X Grip 17 2 X Ray
X-VTAX 9mm Straight trigger, FDE 17 3 VTAC day-night sights
M17 (MS) 9mm Coyote grip & controls RX-type slide, night sights


  • MS: manual safety
  • TB: threaded barrel
States with restrictions are listed next to the model.

Special variants of the P320 are as follows.

M17-Commemorative Edition

An almost exact replica of the M17 pistols marketed to civilians; 5,000 pistols are to be produced. The M17-Commemorative Edition pistols are made to similar, if not the same, specifications as the M17 pistols used by the US Army, with MHS sights and 21-round magazines.[11]

M17 Tomb of the Unknown Soldier Pistol

Commemorative version of the M17 pistols meant to be used for ceremonial purposes. Four pistols, named Silence, Respect, Dignity and Perseverance, have been produced and were presented to the 3rd U.S. Infantry Regiment (the Old Guard) in an official ceremony on 11 October 2018. All four pistols have unique serial numbers and a number of significant features referencing the history of the Tomb and the Old Guard as a whole.[12][13]

Voluntary Upgrade ProgramEdit

In response to a known drop-firing problem with the P320 and M17s in which the gun could voluntarily fire when dropped on the ground at a thirty-three degree angle, SIG Sauer instated a program known as the Voluntary Upgrade Program which upgrades the pistol by making a number of changes to ensure that there is no chance of drop-firing occurring.[14]

The upgrade will be performed free-of-charge, where SIG Sauer will send a "call tag" to a P320 owner to ship their P320 via two-day freight to the SIG Sauer factory in New Hampshire where the upgrade will be performed; SIG Sauer will send the upgrade pistol back to its owner via two-day freight as well. Registering for the upgrade simply requires the user to register for the upgrade on SIG Sauer's website; SIG Sauer will then send the user a prepaid shipping label and instructions on how to pack their P320 for shipping via email or post.[15]

While at the factory, the announced wait time for the upgrade is stated to be about four to six weeks, although apparently actual wait times have been as short as seven days. Owners who received their upgraded P320s also received a 25% discount coupon for a future SIG Sauer purchase along with a SIG Sauer P320 patch.[16]


On 3 May 2017, Steyr Mannlicher filed a lawsuit against SIG Sauer, claiming that the latter had infringed the former's patents on handguns with removable chassis. Referencing patent US6260301 filed in 1999, Steyr Mannlicher demanded a preliminary and permanent injunction against SIG Sauer from selling firearms of this type; however, it appears no action has been taken.[17]


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