The SIG Sauer P320 is a modular striker-fired semi-automatic pistol made by SIG Sauer Inc., SIG Sauer's American branch, and the company's first striker-fired pistol to be commercially released.
In 2017, a customized version of the P320 was selected as the winner of the U.S. military's Modular Handgun System competition, becoming the primary service pistol for the U.S. Army. Following its military adoption, the P320 has been the subject of public scrutiny and litigation regarding its safety, with allegations of unintentional discharges. This has prompted some law enforcement agencies and civilian organizations to discontinue its use. SIG Sauer has maintained that the pistol can only be fired when the trigger is moved to the rear and has been rigorously tested.
According to The Washington Post, the P320 is one of the most popular handguns in the United States.
History The P320 chambered in 9×19mm Parabellum was introduced in the North American market on 15 January 2014, followed by the .45 ACP compact model at the SHOT Show in January 2015.
On January 19, 2017, it was announced that a customized version of the SIG Sauer P320 had won the United States Army's XM17 Modular Handgun System competition. In April 2017, Caracal International was made a licensed producer for the P320.
In December 2025, the SIG Sauer P320 replaced the SIG P220 as the Swiss Army's new service pistol.
Design The P320 is a further development of the SIG Sauer P250, utilizing a striker-fired mechanism in lieu of a double action only hammer system. SIG lists the trigger pull of the standard P320 at . The P320 trigger pull is accomplished by a combination of a tensioned striker spring, ideal trigger shoe and trigger bar dimensions, sear/striker engagement, and a balanced trigger system.
Ammunition The P320 can be chambered in 9×19mm Parabellum, .357 SIG, .40 S&W, .45 ACP, and 10mm Auto and can be easily converted from one caliber to another; a change from .357 SIG to .40 S&W requires only a barrel change; a change from 9mm to .357 SIG or .40 S&W (or vice versa) is accomplished using a caliber exchange kit.
Because of differences in sizes, caliber exchange kits are only available between 9mm, .357 SIG, and .40 S&W. .45 ACP and 10mm require larger components and are not interchangeable with smaller calibers.
Operation The P320 was designed to be ambidextrous in handling, sporting a catch lever on both sides of the slide and a user-reversible magazine release, and all other operating controls are designed to be operated from either side.
The firearm can be field-stripped with no tools.
Additionally, the firearm can be field stripped without depressing the trigger, an additional safety feature to prevent negligent discharge of the weapon during disassembly. The fire control unit is removable, allowing the switch to a different grip size.
Trigger system The P320 trigger shoe is available with a solid, all-metal trigger.
Both curved and straight trigger shoe variants are available from SIG and from third-party aftermarket suppliers.
Variants The full-sized model is known as the M17, and the compact carry-sized model is known as the M18.
X Series models
The X Series lineup includes the following grip module sizes:
Cd .357 SIG. The full-size slide also fits the carry-size grip module without any part of the recoil spring showing. Full size – Fits any SIG P320 full-size slide in 9mm, .40 S&W, and .357 SIG
In January 2019, SIG Sauer announced the XCompact handgun as the newest entry in their X Series lineup.
Compact size – As of March 2020, the P320 XCompact is available in 9mm only.
The XCompact size grip module is the smallest grip module SIG currently carries, as they have not released a subcompact X Series grip module to date.
In May 2022, SIG Sauer announced a 10mm Auto P320 variant, named the P320 XTEN.
M17
The new US Army handgun requirements included a preference for an existing handgun model in the Modular Handgun System Request for Proposal, known as the XM17 Procurement. SIG Sauer submitted a P320 with a number of modifications and submitted it for the XM17 Modular Handgun System competition.
Features include: barrel length in carry size pistol barrel length in full size pistol Ambidextrous thumb safety Chambered in 9×19mm Parabellum (can be adapted to fire larger calibers like .357 SIG, .40 S&W, and .45 ACP) Improved slide sub-assembly to capture small components when disassembled Improved trigger "mud flap" to prevent foreign debris from entering the pistol action Loaded chamber indicator Pistols chambered in 9 mm can feature a 17-round magazine as standard, with optional 21-round extended magazines available. Slide cut-out to facilitate the addition of a reflex sight. (This is the slide from the RX Series)
On January 19, 2017, it was announced that the SIG Sauer P320 MHS variant had won the United States Military's Modular Handgun System trials. The P320 will be known as the M17 (full size) and M18 (compact) in U.S. Military service. Though the pistol will remain chambered in 9 × 19 mm Parabellum rather than a larger caliber, the contract allows the services to procure SIG Sauer's proposed XM1152 Full Metal Jacket and XM1153 Special Purpose ammunition.Army Confirms 9mm for Modular Handgun System - Kitup.Military.com, 26 January 2017.
In May 2017, the Army announced that the first unit that will receive the M17 would be the 101st Airborne Division by the end of the year. At the same time, the rest of the U.S. Armed Forces revealed they also intend to acquire the handgun, making it the standard sidearm for the entire U.S. military. The services plan to procure up to 421,000 weapons in total: 195,000 for the Army, 130,000 for the Air Force, 61,000 for the Navy (XM18 compact version only), and 35,000 for the Marines.MHS Update: Services Embrace Army's New Sidearm - Kitup.Military.com, 3 May 2017.
On 17 November 2017, soldiers of the 101st Airborne received the first XM17 and XM18 pistols, with over 2,000 handguns delivered. The XM17 has better accuracy and ergonomics, and tighter dispersion than the M9. It will also be fielded more widely, being issued down to squad and fireteam leaders; while special forces would dual-arm all of its members with a pistol and rifle; previously, junior leaders in regular infantry units were excluded from carrying sidearms but policy was changed to give them more choices and options in close quarters battle situations. All Army units are planned to replace the M9 with the M17 within a decade.In a first, the Army's new handgun will be issued to team leaders - Armytimes.com, 29 November 2017.
X-Carry
The X-Carry is a larger model of the XCompact featuring 17 rounds per magazine, compared to the Compact's 15 rounds, an enlarged grip, a longer slide, and a smaller slide lock. The X-Carry is the frame used for the M18.
XFive Legion Released in late July/early August 2019, the XFIVE Legion is considered the flagship of the P320 platform that brings added weight and features. The TXG grip module has tungsten-infused directly into the polymer along with an attachable magazine well. It comes standard with Henning group aluminum base pads and a skeletonized flat trigger. The complete 9mm slide has lightening cuts in the top to reduce weight and assist in recoil. It is also optics ready through the removal of the rear sight plate assembly. The optics cut is the Delta Point/Romeo 1 Pro profile, but will accommodate multiple optics via adapter plates.
P320-XTEN The SIG P320-XTENMAX is a 10mm Auto chambered X Series variant of the P320, released in 2022. It features an X Series grip module, bull barrel, flat X Series trigger and a Nitron-finished stainless steel slide with a cut for mounting aiming optics. Magazine capacity is 15 rounds. It weighs , has a bull barrel, overall length of , overall height of , overall width of and a sight radius of .
P320MAX The SIG P320MAX is a sporterised variant of the P320, designed in 2021 for use by competition shooters. The pistol comes with ROMEO3 MAX sights and tungsten infused TXG heavy grip module, weighs , has a match grade barrel, and an overall length of .
P320AXG The SIG P320AXG was the first P320 offered with a metal grip module. The first model was the 320AXG Scorpion and was launched in 2021. It was followed by the Equinox, Combat, and several other models later in the year. Its metal alloy grip module offered a new level of solidity and stiffness to the P320 platform and allowed for numerous colors, finishes, and aftermarket grip panels. The P320AXG Legion, released in April 2023, was offered with a Legion gray Cerakote finish, Hogue Legion grips and an integrated slide compensator. All P320AXG models come standard with XRay3 day-night sights and are offered with and without Romeo red dot optics.
P320SXG The SIG P320SXG XFIVE was launched in November 2024, and was the first P320 offered with a heavy steel grip module. This was the heaviest P320 ever made at in weight. Designed for the serious competitive shooter, the P320SXG XFIVE offered a 5" bull barrel, adjustable sights, an SXG full-length grip module and LOK G10 grip panels. The P320SXG grip was also offered in the P320 Reserve featuring a carry-length SXG grip module, integrated slide compensator and a high-polish finish.
Military adoption In January 2017, the SIG Sauer P320 was selected as the winner of the U.S. Army's Modular Handgun System (MHS) competition, a program intended to replace the Beretta M9 as the standard U.S. military sidearm. Designated the XM17 and XM18, the pistols were adopted under a joint-service procurement program that allowed the other military branches to purchase additional units.
Problems
Drop firing Initial production models of the P320 were found to have a "drop safety" vulnerability if the firearm was dropped at a specific angle and height outside of SAAMI and NATO standards, potentially causing it to discharge. SIG Sauer has since refitted the P320 to further improve its drop safety and offers a voluntary upgrade program for early P320s.
In late July 2017, the Dallas Police Department in Texas instructed all personnel to stop carrying the P320 pending an investigation. There were concerns that the firearm may discharge when it is dropped and the back of the slide hits the ground at a 33-degree angle. The problem was thought to be related to the trigger weight; some triggers were heavy enough that they essentially continued to move due to inertia after the gun hit the ground.
On 8 August 2017, SIG Sauer issued a notice that they would upgrade all P320s to address the issue. The upgrade is described on the company's website as: "an alternate design that reduces the physical weight of the trigger, sear, and striker while additionally adding a mechanical disconnector."
Issues of drop firing or shooting its user in the leg while holstered have continued sporadically with at least six departments removing the P320 from service.
Reports of misfiring Around 400 P320s were procured for the Canadian Joint Task Force 2 special forces unit (JTF-2) in 2019, but these were withdrawn and the earlier P226 pistols (also manufactured by SIG Sauer) reinstated following a misfire that injured a soldier during a training exercise in November 2020; JTF-2 was the only Canadian military unit using the P320 at the time.
In June 2021, a technical investigation found that the misfire was due to "a partial depression of the trigger by a foreign object combined with simultaneous movement of the slide [...] that then allowed a round to be fired whilst the pistol was still holstered" and that the usage of a holster designed for a different pistol was a contributory factor. The investigation did not identify issues with how the pistol had been procured by Canadian defence officials, though questions had been raised as to whether these officials were aware of the drop safety issues.