SIG Sauer P320

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SIG Sauer P320
Sig Sauer P320 Modular Handgun System.jpg
SIG Sauer P320
Type Semi-automatic pistol
Place of origin U.S.
Service history
In service 2014–present
Production history
Designer Adrian Thomele, Thomas Metzger, Michael Mayerl, Ethan Lessard
Designed 2014
Manufacturer SIG Sauer Inc., Exeter, NH, United States,= SIG Sauer GmbH, Eckernförde, Germany
Produced 2014-present
Variants Full-size, Carry, Compact, and Subcompact, four calibers, three grip sizes for each, Tacops, RX and X-Five models
Weight 833 g (29.4 oz) P320 Full Size (incl. magazine)
737 g (26.0 oz) P320 Carry (incl. magazine)
737 g (26.0 oz) P320 Compact (incl. magazine)
708 g (25.0 oz) P320 Subcompact (incl. magazine)
Length 203 mm (8.0 in) P320 Full Size
183 mm (7.2 in) P320 Carry
183 mm (7.2 in) P320 Compact
170 mm (6.7 in) P320 Subcompact
Barrel length 120 mm (4.7 in) P320 Full Size
98 mm (3.9 in) P320 Carry
98 mm (3.9 in) P320 Compact
91 mm (3.6 in) P320 Subcompact
Width 35.5 mm (1.4 in) P320 Full Size
35.5 mm (1.4 in) P320 Carry
35.5 mm (1.4 in) P320 Compact
33 mm (1.3 in) P320 Subcompact
Height 140 mm (5.5 in) P320 Full Size
140 mm (5.5 in) P320 Carry
131 mm (5.2 in) P320 Compact
119 mm (4.7 in) P320 Subcompact

Caliber 9×19mm Parabellum
.357 SIG
.40 S&W
.45 ACP
Action Short recoil operated, locked breech Sig Sauer System
Rate of fire Semi-automatic
Feed system

P320 Full Size and P320 Full Size RX models:

Tacops Full:


Tacops Carry:


RX Compact:


Sights Fixed iron sights, front—blade, rear—notch, with optional tritium night inserts, Optical Reflex sight on RX models, high sights on RX and Tacops models

The SIG Sauer P320 is a modular design of semi-automatic pistol made by Sig Sauer, Inc. of Exeter, New Hampshire and SIG Sauer GmbH of Eckernförde, Germany. The SIG Sauer P320 can be chambered in 9×19mm Parabellum (referred to in the U.S. as 9mm Luger), .357 SIG, .40 S&W, and .45 ACP. The handguns made in 9mm, .357 SIG, and .40 S&W calibers can be easily converted from one to another. A change from .357 Sig to .40 S&W requires only a barrel change. The change between 9mm to .357 Sig or .40 S&W and vice versa are accomplished using a caliber exchange kit.

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.[1] 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. 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 will be known as the M17 and the carry sized model will be known as the M18.[2]

Design details[edit]


Sig Sauer P320 fire control unit

A key feature of the pistol is its modular design. The main module of the P320 is an internal stainless steel fire control unit, which consists of the integrated fire control group (trigger, and all necessary linkage and springs), ambidextrous slide release (one on each side of the pistol), ejector and four slide rails as well as an ambidextrous external safety on handguns so equipped. This steel receiver unit is used in every P320 grip module, top end, and chambering combination and is inserted into the grip frame module and held in place by the axis pin of the disassembly lever. The firearm's serial number is on the fire control unit instead of the grip module. The fire control unit allows the operator to interchange differently-sized slide assembly or top end modules and polymer grip frame modules and trigger shoes and (limited) chambering conversions to adapt the gun to the individual user and address different needs.

Calibers and grip choices[edit]

Each of these three calibers (9x19mm Parabellum, .357 Sig, and .40 S&W) comes in four barrel/slide sizes, which can be changed back and forth using caliber exchange kits. A 9mm full size can be changed to a 9mm carry, compact, or subcompact in this manner (as can any of the 3 calibers). Or a 9mm full size can be changed to .357 Sig carry (for example). In addition to the basic P320 models are the RX series which feature optical sights built in. Another P320 variation is the X Series. The RX features are also available to standard models through caliber exchange kits, and vice versa. These parts are not firearms and are not serialized and can be sold and shipped with no restriction. Models with .357 Sig and .40 S&W caliber barrels change exchange these calibers using just the barrel.

The Sig Sauer P320 handguns use polymer grip frames which can be changed from between of four sizes of frames and three sizes of grips. In this manner the size of the grip is matched to the length of the handgun action as well as being available in three grip sizes. The four chassis sizes are full, carry, compact, and sub compact. The three grip sizes are large, medium, and small. The .45 ACP caliber is not interchangeable with the other calibers but does have varying grip sizes too. Most of the grip sizes have a standard Picatinny accessory rail, except for subcompact grips.

The X series grips can also exchange with the standard grips.

Fire control unit/serialization[edit]

The firearms serial number, which is used for registration and tracking by the government, is part of the one part that is not changeable with regard to registration and is in effect the firearm regardless of which of the frame or grip sizes is attached to it. The Fire Control Unit (FCU) contains the trigger, striker, disconnector, and safety mechanisms. This is, in effect, the firearm while all the interchangeable barrels, slides, recoil springs, grips, and magazines involved are merely accessory pieces and are not subject to registration of restrictions (U.S. regulations). The ability to change caliber, frame size, and grip size is the essence of the modular system.

The P320 was designed to be ambidextrous in handling, sporting an ambidextrous slide catch lever and user-reversible magazine catch. 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.[3]

The full-size, carry and compact grip modules feature an integral Picatinny rail mounting-bracket at the lower forward edge of the module to allow the mounting of laser sights, tactical lights, and other accessories.

Modular options[edit]

Sig Sauer P320 Full Size

The P320 pistol is offered in three Glass-filled polymer grip module sizes—small, medium, and large—in each of the full-sized, carry, compact, and subcompact P320 variants. The pistol top ends also come in full-sized, compact, and subcompact variants that will fit the correspondingly sized grip modules. Every chambering can be converted by the user with a caliber exchange kit. The 9×19mm Parabellum, .40 S&W, and .357 SIG chamberings share their polymer grip frame modules and this offers the possibility to interchange these three chamberings by swapping the top end—consisting of the slide, recoil spring assembly, barrel and the box magazine. Due to the significantly larger external dimensions of the .45 ACP cartridge compared to the other P320 chambering options, the .45 ACP chambering uses slightly wider .45 ACP–specific polymer grip modules with an enlarged magazine well. The firearm's "fire control group", which contains the only serialized part of the firearm, is also slightly different to accommodate the enlarged magazine well.

Grips come in various color patterns depending on handgun model. Some are offered in Flat Dark Earth, such as the M17 Civilian model, the color is called Coyote.

Caliber exchange kits[edit]

The manufacturer offers caliber exchange kits or Caliber X-Change® kits consisting of a slide, recoil assembly, barrel, box magazine and grip module in the varying frame sizes, grip module sizes and chambering variants in which the P320 pistol is offered. These kits enable a user to switch between the various P320 configurations without the use of tools. There is also a caliber exchange kit which supplies the mounted Reflex Optic sight of the RX model.

Recoil mechanism[edit]

Like other SIG Sauer pistols, the P320 pistol is a short recoil operated, locked breech pistol. It uses the Sig Sauer System cam-operated barrel, which locks into the ejection port on the slide.


The slide is made of stainless steel and is often finished in a durable black finish called Nitron®. The slide contains the breechblock, striker, disconnector, ejector, and safety systems. State compliant versions may also mount an ambidextrous external safety lever. Some slides are machined for the Romeo1 type of optical sight.

Safety mechanisms[edit]

The standard P320 has no manual safeties, promoting instant readiness. The use of an automatic firing pin safety combined with a disconnector ensures safe carrying of the weapon, while preventing accidental discharges if the gun is dropped or roughly handled. As mandated in some U.S. states, some models come with an external safety. The Modular Handgun System (MHS) (now known as the M17) version of the P320 has an ambidextrous thumb safety. Law enforcement and military versions can also be equipped with a tabbed safety trigger on request.

No trigger pull needed[edit]

The firearm can be disassembled for cleaning without having to pull the trigger simply by using the hold open lever to lock the slide back, then turning the takedown lever to its most counter clockwise position and then releasing the slide by pressing the hold open lever downward and then easing the slide forward off of the rails of the fire control unit.

Trigger system[edit]

The trigger releases a pretensioned Double Action striker. The trigger system has a pull weight of about 5.5 lbs., 28.95 N[4]

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


The P320 is available with a 120 mm (4.7 in), 98 mm (3.9 in), or 91 mm (3.6 in) barrel depending on the size (full-sized, carry/compact or sub-compact respectively). The Tacops model barrel is threaded for suppressor (also called a silencer) use.

Model size Barrel length Threaded
X-Five 5
Full 4.7
Carry 3.9 4.6
Compact 3.9
Subcompact 3.6

Ammunition feeding[edit]

The pistol feeds from metal detachable box magazines with a 6 to 21 round magazine capacity, depending on caliber (9x19mm Parabellum, .357 Sig, .40 S&W, or .45 ACP) and pistol size. See the chart under the Variants section.


The P320 comes with three-dot combat-type iron sights of which the front sight element can be drifted to the left or right in its dovetail to adjust for windage. There are three rear sight heights and six front sight heights available to adjust for elevation. Self-luminous tritium-powered SIGLITE Night Sights in differing heights are optional. SIGLITE night sights are optional, but come standard in exchange kits.

The SIG Sauer Romeo1 sight is supplied on the RX Full and RX Compact versions of the P320.[6]

The X-Five comes with Dawson Precision Fiber Optic front sight and a fully adjustable rear sight.[7]

Field stripping[edit]

Field stripping is accomplished by first locking the action open with the hold open lever either by racking the slide to the rear with an empty magazine which will engage the slide hold open lever when the slide is released, or by holding the slide to the rear and then pushing up the slide hold open lever. The magazine is then removed. Then the takedown lever on the left side of the frame is revolved downward. The slide hold open lever is then pushed down while holding onto the slide assembly which can then be removed from its engagement with the fire control units stainless steel rails. Once removed the barrel can be removed from the slide by pushing the recoil spring, located under the barrel away from the breech block which allows the spring to be removed. Then the barrel can be pivoted downward away from the slide breech end first and then removed from the front of the slid bushing. Cleaning can be easily accomplished from this point on.

Reassembly requires that the slide be locked open with the slide hold open lever (and then released or left open) or the magazine cannot be reinserted.

Removing the fire control unit[edit]

A Sig Sauer P320 Fire Control Unit with take down lever and grip module

Changing grip modules is very easy and simple. It begins with the removal of the slide as noted above. Once the slide assembly is removed the takedown lever can be removed from the frame by pulling it out from the left side. Then the Fire Control Unit (FCU) can be pivoted out of the grip. The FCU can then be easily inserted into a different grip size and if desired a different slide assembly can be used with that different frame. This is the essence of the configurability of the modular system.


The factory accessories consist of magazines, caliber exchange kits, barrels, handgun holsters, Optical Sights, and Tactical Light/Laser units.


In the chart below the presence of MS in the model indicates a model with manual external ambidextrous safety. The presence of TB in the model indicates Threaded Barrel. Siglights are tritium illuminated Night Sights. States that have restrictions are listed next to the model. These relate to manual safety and magazine capacity in most cases.

The X-Five model has a 5" bull barrel. X model has a different grip and flat trigger.

*M17 is in Coyote for grip and controls. Available with and without the external manual safety. Comes with RX type slide and night sights.

Model Caliber State Compliant Mag Cap #of Mags Sights
Nitron Full 9mm CT/HI/NY 10 2 Siglight
Nitron Full 9mm 17 2 Siglight
Nitron Full .40 S&W CT/HI/NY 10 2 Siglight
Nitron Full .40 S&W 14 2 Siglight
Nitron Full .45 ACP CT/HI/NY 10 2 Contrast Sights
Nitron Full .45 ACP 10 2 Siglight
Nitron Compact 9mm CT/HI/MO/NY 10 2 Contrast Sights
Nitron Compact 9mm CT/HI/MO/NY 10 2 Siglight
Nitron Compact MS 9mm MA 10 2 Siglight
Nitron Compact 9mm 15 2 Siglight
Nitron Compact TB 9mm 15 2 Siglight
Nitron Compact MS 9mm 15 2 Siglight
Nitron Compact .40 S&W CT/HI/MO/NY 10 2 Contrast Sights
Nitron Compact .40 S&W CT/HI/MO/NY 10 2 Siglight
Nitron Compact .40 S&W 13 2 Siglight
Nitron Compact .45 ACP 9 2 Contrast Sights
Nitron Compact MS .45 ACP MA 9 2 Siglight
Nitron Compact MS .45 ACP 9 2 Siglight
Nitron Carry 9mm CT/HI/NY 10 2 Siglight
Nitron Carry 9mm 17 2 Siglight
Nitron Carry TB 9mm 10 2 Siglight
Nitron Carry 357 Sig CT/HI/NY 10 2 Siglight
Nitron Carry 9mm 14 2 Siglight
Nitron Carry .40 S&W CT/HI/NY 10 2 Siglight
Nitron SubCompact 9mm 12 2 Siglight
Nitron SubCompact .40 S&W 10 2 Siglight
FDE Compact 9mm 10 2 Siglight
FDE Compact 9mm 15 2 Siglight
FDE Compact .35 Sig 10 2 Siglight
FDE Compact .40 S&W 10 2 Siglight
Tacops Full 9mm 21 4 TFD Frt, Siglight Rr
Tacops Carry TB 9mm 21 4 Tall Slite Night Sights
X-Five Full 9mm 5" Barrel 21 4 Dawson Fiber Optic
RX Full 9mm CT/HI/NY 10 2 Siglight
RX Full 9mm 17 2 Siglight
RX Compact 9mm CT/HI/NY 15 2 Tall Slite Night Sights
RX Compact 9mm CT/HI/NY 10 2 Siglight
RX Compact 9mm CT/HI/NY 15 2 Siglight
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


M17 and M18[edit]

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)[9]
  • 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.[10][11]

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.[12][13] 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.[14][15]

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.[16][17]

Drop firing problem[edit]

In late July 2017, the Dallas Police Department in Texas instructed all personnel to stop carrying the P320 pending an investigation.[18] There are 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 may be related to the trigger weight; some triggers are heavy enough that they essentially continue to move due to inertia after the gun hits the ground. Internet publications, such as, conducted independent tests that appear to confirm potential drop firings (at a 40% rate).[19] Another test has shown that the P320 may discharge when the magazine hits the ground first after the gun is dropped.[20]

On 8 August 2017, Sig Sauer issued a notice that they would upgrade all P320s to address the issue.[21] The P320 upgrade program is detailed on the Sig Sauer Website at: P320 Voluntary Upgrade Program.

Voluntary upgrade program[edit]

Although the P320 handgun had successfully passed the MH17 drop protocol tests it became apparent later than the gun could fire if dropped in a specific fashion onto a hard surface. In one instance a gun writer installed a lighter trigger which almost totally eliminated the possibility of accidentally firing. Sig Sauer instituted a program for those who wanted to upgrade their P320 handguns whereby a number of changes are made which ensure that no drop discharges are likely to occur. The details of the changes are found here: Explanation of Changes Made To The P320 Pistol

The upgrade program entails no cost to the owner. Sig Sauer sends a "call tag" to the owner who ships the firearm at no cost by 2 day freight to Sig's factory for the upgrade. After the upgrade is performed the handgun is shipped back to the owner, again by 2 day freight. To participate in the upgrade program a user goes to the Sig Sauer website as shown above and registers for the upgrade. Sig Sauer will send to the user a prepaid shipping label and instruction on how to pack the firearm for legal shipment. Details will generally be sent by email, or post if the owner does not have email. Once the firearm arrives at Sig Sauer the announced wait time is from four to six weeks. Actual turnaround time has been as short as 7 days. Once shipped the owner will be notified of the shipment and given a tracking number. SIG SAUER Announces Details of Free P320 ‘Voluntary Upgrade’ Program

Owners who have received their P320s back after the upgrade report that they are also being given a Sig P320 Patch and a 25% discount coupon for a future purchase from the Sig Sauer store.

Patent infringement lawsuit[edit]

In May 2017, Steyr Mannlicher filed a patent infringement lawsuit against Sig Sauer.[22] Steyr references their patent US6260301 (filed in 1999 and approved in 2001), which is for a handgun with a removable chassis. Steyr Arms is demanding a preliminary and permanent injunction against Sig Sauer selling any of these firearms.



  1. ^ "SHOT Show 2015: SIG SAUER adds subcompact and .45-Caliber options to P320 family". Retrieved 28 February 2017. 
  2. ^ OMelveny, Sean. "Army Picks Sig Sauer's P320 Handgun to Replace M9 Service Pistol". Retrieved 28 February 2017. 
  3. ^ "P320 Pistol -". Retrieved 28 February 2017. 
  4. ^ "SIG SAUER P320". Retrieved 11 March 2017. 
  5. ^ "Review: SIG Sauer P320 Pistol". Retrieved 11 March 2017. 
  6. ^ "Gun Review: SIG SAUER P320 RX Compact". Retrieved 11 March 2017. 
  7. ^ "P320 X-Five Full-Size". Sig Sauer. Retrieved 15 January 2018. 
  8. ^ "SIG SAUER 2018 Product Catalog". Retrieved 19 January 2018. 
  9. ^ "Details on the U.S. Army's new Sig Sauer M17 Sidearm". Retrieved 11 March 2017. 
  10. ^ "SIG SAUER Unveils the P320 MHS Edition - The Truth About Guns". 18 October 2014. Retrieved 28 February 2017. 
  11. ^ Times, Military. "GearScout". Retrieved 28 February 2017. 
  12. ^ "Contracts Press Operations Release No: CR-012-17 Jan. 19, 2017". Retrieved 13 February 2017. Sig Sauer Inc., Newington, New Hampshire, was awarded up to $580,217,000 for a firm-fixed-price contract for the Modular Handgun System including handgun, accessories and ammunition to replace the current M9 handgun. Bids were solicited via the Internet with nine received. Work locations and funding will be determined with each order, with an estimated completion date of Jan. 19, 2027. Army Contracting Command, Picatinny Arsenal, New Jersey, is the contracting activity (W15QKN-17-D-0016). 
  13. ^ Army Confirms 9mm for Modular Handgun System -, 26 January 2017
  14. ^ Army Names First Unit to Receive Service's New Pistol -, 3 May 2017
  15. ^ MHS Update: Services Embrace Army’s New Sidearm -, 3 May 2017
  16. ^ In a first, the Army’s new handgun will be issued to team leaders -, 29 November 2017
  17. ^ Army Explains New Dual-Arming Policy for Modular Handgun System -, 1 December 2017
  18. ^ "BREAKING: P320 Recall Issued By Dallas Police - Prohibited From Duty Till Repaired - The Firearm Blog". 2 August 2017. 
  19. ^ "BREAKING: TTAG Test Shows P320 Striker-Fired Pistols Are Not Drop-Safe - The Truth About Guns". 8 August 2017. 
  20. ^ "Sig Sauer P320 Fails Drop Test". 7 August 2017. 
  21. ^ "SIG SAUER Issues Voluntary Upgrade of P320 Pistol - Sig Sauer". 
  22. ^ "Steyr Files Lawsuit Against SIG SAUER, Demands Injunction Against P320 for Patent Infringement - The Truth About Guns". 5 May 2017. 
  23. ^ "Forsvarets nye pistol: Sig Sauer". 12 April 2018. 
  24. ^ "Den nye pistol er valgt". 12 April 2018. 
  25. ^ "Police chief to seek approval from ministry to make direct order of 150,000 Sig Sauer pistols". Thai PBS. 21 August 2015. Retrieved 21 August 2015. 
  26. ^ "Gen Prayut Chan-o-cha Approves Royal Thai Police's Purchase of 152,468 SIG Sauer Model P320 Pistols". Chiang Rai Retrieved 28 February 2017. 
  27. ^ "Claims of gangsters buying police pistols are false, says RTP spokesman". The Nation. 24 December 2017. Retrieved 24 December 2017. 
  28. ^ "US Department of Defense Contracts". 19 January 2017. Sig Sauer Inc., Newington, New Hampshire, was awarded up to $580,217,000 for a firm-fixed-price contract for the Modular Handgun System including handgun, accessories and ammunition to replace the current M9 handgun. Bids were solicited via the Internet with nine received. Work locations and funding will be determined with each order, with an estimated completion date of Jan. 19, 2027. Army Contracting Command, Picatinny Arsenal, New Jersey, is the contracting activity (W15QKN-17-D-0016). 
  29. ^ "Army". 
  30. ^ "Hawaii DPS". 
  31. ^ "CPD U04-02-01" (PDF). 
  32. ^ "Oklahoma Highway Patrol Selects SIG SAUER P320". SIG Sauer. 22 June 2015. Archived from the original on 5 September 2015. 
  33. ^ "Pasco sheriff's deputies trade in Glocks for free SIG Sauer service handguns". Tamba Bay Times. 20 May 2016. Retrieved 6 August 2016. 
  34. ^ "Alameda County Sheriff's Department" (PDF). Alameda County Sheriff's Department. Retrieved 2 May 2018. 
  35. ^ "Texas Department of Public Safety Selects SIG SAUER P320 | Sig Sauer". Sig Sauer. Retrieved 2018-06-23. 

External links[edit]