SIG Sauer P320
The SIG Sauer P320 is a modular striker-fired semi-automatic pistol made by SIG Sauer, Inc., SIG Sauer's American branch. It marked Sig Sauer's first foray into striker-fired pistols, as their first offering on the commercial market.
The P320 has faced scrutiny over reports of unintentional discharges and safety issues, leading to over 100 lawsuits against SIG Sauer, and its withdrawal from use by several law enforcement agencies, United States Immigration and Customs Enforcement as well as being banned from use in IDPA-sanctioned competitions and numerous ranges and training courses.
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 19 January 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.
The full-sized model is known as the M17 and the compact carry-sized model is known as the M18.
On 9 July 2025, United States Immigration and Customs Enforcement issued a memorandum stating all models of the SIG Sauer P320 were no longer approved and officers must replace them with Glock 19 MOS pistols.
According to The Washington Post, the P320 is one of the most popular handguns in the United States.
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. To achieve this relatively light trigger pull, the striker mechanism's striker spring is kept by a relatively small margin under its final firing tension.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 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 user-reversible magazine release, and all other operating controls are designed so they can 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. The fire control unit is removable, allowing the switch to a different grip size.
Trigger system
The P320 trigger shoe is available in an all-metal, solid trigger.Both curved and straight trigger shoe variants are available from SIG and from third-party aftermarket suppliers.
Variants
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
- Compact size – As of March 2020, the P320 XCompact is available in 9mm only.
In May 2022, SIG Sauer announced a 10mm Auto P320 variant, named the P320 XTEN.
M17
The requirements for the new US Army handgun included the requirement that an existing handgun model would be preferred for the Modular Handgun System Request for Proposal, known as the XM17 Procurement. SIG Sauer submitted a P320 with a number of modifications and submitted them for the XM17 Modular Handgun System competition.Modifications include:
- barrel length in carry size pistol
- barrel length in full size pistol
- Ambidextrous thumb safety
- Chambered in 9×19mm Parabellum
- 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.
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, and 35,000 for the Marines.
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 have the M9 replaced with the M17 within a decade.
X-Carry
The X-Carry is a larger model of the XCompact featuring 17 rounds per magazine, compared to the Compact's 15 rounds, enlarged grip, 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.Problems
Drop firing
Initial production models of the P320 were found to have a "drop safety" issue if the firearm was dropped at a specific angle, potentially causing it to discharge. SIG Sauer has since refitted the P320 to make it drop-safe 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. Internet publications, such as TheTruthAboutGuns.com, conducted independent tests that appeared to confirm potential drop firings.
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.
Misfiring
Around 400 P320s were procured for the Canadian Joint Task Force 2 special forces unit in 2019, but these were withdrawn and the earlier P226 pistols 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.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 P320 itself was not at fault nor were there any issues with how it had been procured by Canadian defence officials.
However, the pistols would remain in storage pending a third-party safety assessment.
The safety assessment and other proceedings related to the misfire were concluded by June 2022, with a decision to reinstate the P320 being taken towards the end of that month.