SIG Sauer P320

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 also be field stripped without depressing the trigger, an additional safety feature to prevent negligent discharge of the weapon.[4]

SIG Sauer P320 fire control unit

The P320 trigger is available in standard (solid) and tabbed (with trigger safety).[5]

When the requirements were formulated for a new handgun for the US Army one of the tenets of the proposal was that an existing model handgun was desired to fulfill the requirements laid out 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 them for the XM17 Modular Handgun System competition.

Modifications include:

• Slide cut-out to facilitate the addition of a reflex sight. (This is the slide from the RX Series)[6]
• Ambidextrous thumb safety
• Loaded chamber indicator
• Improved slide sub-assembly to capture small components when disassembled
• Improved trigger "mud flap" to prevent foreign debris from entering the pistol action
• 4.7-inch (120 mm) barrel length in full size pistol
• 3.9-inch (99 mm) barrel length in compact pistol
• chambered in 9×19mm Parabellum (can be adapted to fire larger calibers like .357 SIG and .40 S&W)
• Pistols chambered in 9mm can feature a 17-round magazine as standard with optional 21-round extended magazines available.[7]

On 19 January 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 x 19mm 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.[8][9] The ammunition chosen to go with the pistol is a "Winchester jacketed hollow point" round.

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.[10][11]

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.[12][13]

Initial production models of the P320 were noted to have a 'drop safety' issue if the firearm was dropped on a specific angle causing it to discharge. Sig has since refitted the P320 with a new trigger with reduced mass and a new striker disconnect that makes it drop safe. Sig also offers a voluntary exchange program to fix any defective P320s.

Apart from initial teething issues, the P320 has proven itself to be an extremely reliable pistol for civilian, law enforcement and military use. Many police departments in the US and around the world have started issuing their officers P320s.[14][15][16][17]

SIG Sauer P320 Full Size

SIG Sauer P320 Compact

The X Series lineup includes the following grip module sizes:

• Full size – Fits any SIG P320 full-size slide in 9mm, .40 S&W, and .357 SIG
• Carry size – Fits any SIG P320 compact-size slide in 9mm, .40 S&W, and .357 SIG. The full-size slide also fits the carry-size grip module without any part of the recoil spring showing.

In January 2019, SIG Sauer announced the XCompact handgun as the newest entry in their X Series lineup.[18]

• Compact size – As of March 2020, the P320 XCompact is available in 9mm only.[19]

The XCompact size grip module is the smallest grip module SIG currently carries, as they have not come out with a subcompact X Series grip module to date.

Release in late July/early August of 2019 the XFIVE Legion is considered the flagship of the P320 platform that brings a balance of 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 is cut and ported to reduce weight and assist in recoil and feeding abilities. It also has a slide plate for optic capabilities.[20]

In May 2017, Steyr Mannlicher filed a patent infringement lawsuit against SIG Sauer.[25] Steyr refers to their patent US6260301 (filed in 1999 and approved in 2001),[26] which is for a handgun with a removable chassis. Steyr Arms requested a preliminary and permanent injunction against SIG Sauer selling any such firearms. On March 11, 2020, the United States District Court for the District of New Hampshire found that SIG Sauer did not infringe Steyr’s patents, and dismissed all motions.[27]

A lawsuit related to the above noted drop firing problem and filed in April 2018 in the United States District Court for the Western District of Missouri led to a class action settlement in February 2020.[28][29][30] Elements of the agreement include:[29]

• Communication that the mechanical disconnector added via the P320 voluntary upgrade program "provides an additional level of safety," to be advised via the SIG Sauer website and direct customer communication
• Extension of the voluntary upgrade program for 24 months past the settlement date
• For anyone who submitted their P320 to the voluntary upgrade program and was told it was unrepairable, a refund of the purchase price or a new P320
• For anyone who submitted their P320 to the voluntary upgrade program and was charged for repairs, a refund of such charges

A class action settlement form is available on the SIG Sauer website.[31]

In September 2019, an Arizona gun owner who purchased a P320 in September 2016 initiated a class action lawsuit.[32] It claims that SIG Sauer "continued to sell the flawed gun to the public",[32] and that the upgrade offered "would still not fully compensate him for the significantly diminished resale value of his pistol."[33] In March 2020, judge Joseph N. Laplante denied SIG Sauer's motion to dismiss the case.[34][33]