View source for SIG SG 540

{{Infobox weapon
| name               = SG 540
| image              = File:SG 540 Manurhin noBG.png
| image_size         = 300
| caption            = The SIG SG 540 with fixed stock
| origin             = Switzerland
| type               = [[Assault rifle]] (SG-540)<br />[[Carbine]] (SG-543)<br />[[Battle Rifle]] (SG-542)
<!-- Type selection -->| is_ranged          = Yes
<!-- Service history -->| service            = 1977–present
| used_by            = See ''[[#Users|Users]]''
| wars               = [[Lebanese Civil War]]<ref name ="Lebanon">{{cite book|title=Armies in Lebanon 1982–84|url=https://archive.org/details/armieslebanon00katz|url-access=limited|series=Men-at-Arms 165|first1=Sam|last1= Katz|first2= Lee E|last2= Russell|date=25 Jul 1985|isbn=9780850456028|publisher=[[Osprey Publishing]]|pages=[https://archive.org/details/armieslebanon00katz/page/n15 16], 40}}</ref><br/>[[The Troubles]]<br>[[Somali Civil War]]<br/>[[Ivorian Civil War (disambiguation)|Ivorian Civil War]]s<br/>[[Syrian Civil War]]<br/>[[Militias-Comando Vermelho conflict]]<ref>{{Cite web |date=2017-02-21 |title=Weapons of Rio's crime war - |url=https://www.thefirearmblog.com/blog/2017/02/21/weapons-rios-crime-war/ |access-date=2022-11-03 |website=The Firearm Blog |language=en-US}}</ref>
<!-- Production history -->| designer           = [[Schweizerische Industrie Gesellschaft]] (SIG)
| design_date        = 1970s
| manufacturer       = [[Manurhin]] ([[France]])<br />[[INDEP]] ([[Portugal]])<br />[[FAMAE]] ([[Chile]])
| unit_cost          = 
| production_date    = 1977–2002<ref name="janes">{{cite book  | last =Hogg  | first =Ian  |author2=Gander, Terry   | title =Jane's Guns Recognition Guide  | edition = 4th   | year =2005  | publisher =HarperCollins Publishers  | location =New York, NY  | pages = 323  | isbn = 0-00-718328-3 }}</ref>
| number             = 
| variants           = SG 542, SG 543
<!-- General specifications -->| spec_label         = 
| weight             = SG 540: {{convert|3.52|kg|lb|2|abbr=on}} fixed stock<br/> SG 542: {{convert|3.55|kg|abbr=on}}<br/>SG 543: {{convert|3|kg|abbr=on}} folding stock
| length             = SG 540: {{convert|950|mm|in|1|abbr=on}} stock extended / {{convert|733|mm|abbr=on|1}} stock folded<br />SG 542: {{convert|1000|mm|abbr=on|1}} stock extended / {{convert|754|mm|abbr=on|1}} stock folded<br/> SG 543: {{convert|805|mm|abbr=on|1}} stock extended / {{convert|569|mm|abbr=on|1}} stock folded
| part_length        = SG 540: {{convert|460|mm|abbr=on|1}}<br/> SG 542: {{convert|465|mm|abbr=on|1}}<br />SG 543: {{convert|300|mm|abbr=on|1}}
| width              = 
| height             = <!-- Ranged weapon specifications -->
| cartridge          = SG 540, SG 543: [[5.56×45mm NATO]]<br/>SG 542: [[7.62×51mm NATO]]
| action             = [[Gas-operated reloading|Gas-operated]], [[rotating bolt]]
| rate               = 650–800 rounds/min
| velocity           = SG 540: {{convert|980|m/s|0|abbr=on}}<br/> SG 542: {{convert|820|m/s|abbr=on|1}}<br />SG 543: {{convert|875|m/s|abbr=on|1}}
| range              = 100–500 m sight adjustments
| max_range          = 
| feed               = 20- or 30-round detachable [[box magazine]]
| sights             = Rear: rotating diopter drum; front: hooded post
}}

The '''SG 540''' is a [[5.56×45mm NATO]] [[assault rifle]] developed in the early 1970s by [[Schweizerische Industrie Gesellschaft]] (SIG, currently SAN [[Swiss Arms]] AG)  of [[Neuhausen am Rheinfall|Neuhausen]], Switzerland  <ref name="ModernFirearms-SG540">{{cite web|title=SIG SG-540 SG-542 SG-543 assault rifles|url=http://modernfirearms.net/assault/switch/sig-540--542--543-e.html|website=modernfirearms.net|date=27 October 2010|access-date=27 February 2017}}</ref> as a private venture primarily destined for export markets and as a potential replacement for the [[7.5×55mm Swiss]] [[SIG SG 510|SG 510]] [[automatic rifle]] known as the Stgw 57 in Swiss service.

==History==
Work on a new generation of lightweight rifle using the intermediate 5.56mm round began at SIG in the 1960s and resulted in the somewhat unsuccessful [[SIG SG 530|SG 530-1]] design that employed a [[Gas-operated reloading|gas-assisted]] [[Blowback (arms)#Delayed blowback systems#Roller delayed|roller-delayed blowback]] operating mechanism which proved too complicated and expensive to manufacture. As a result, in 1969 SIG chose to dispense with the complex roller-delayed action opting instead for a design using the more robust and simple piston-operated [[rotating bolt]] locking mechanism (derived from the [[Soviet Union|Soviet]] [[7.62×39mm]] [[AK-47]] assault rifle). This combination proved successful and the rifle entered production as a family of weapons consisting of the base 5.56mm SG 540, the 7.62mm '''SG 542''' battle rifle and the 5.56mm '''SG 543''' [[carbine]], where both 5.56mm variants were designed for use with 5.56×45mm M193 ammunition, while the SG 542—the full size [[7.62×51mm NATO]] rifle cartridge.

Production began between 1973 and 1974, but due to Swiss federal restrictions on firearms exportation, manufacturing had to be carried out at the [[Manurhin]] (''Manufacture de Machines du Haut Rhin'') facility in [[Mulhouse]], France.

The SG 540 series has entered service with the armed forces of several countries in [[Africa]], [[Asia]] and [[South America]] as well as numerous law enforcement and security services. In 1988, the nationally owned Portuguese defense manufacturer [[INDEP]] purchased rights to license build the SG 543 carbine for its own forces. Currently the SG 540, SG 542, and the SG 543 are manufactured in Chile, under license by [[FAMAE]] for the [[Chilean Armed Forces]]. Based on the SG 540, FAMAE developed a [[9×19mm Parabellum]] [[submachine gun]] version of the weapon known as the '''[[FAMAE SAF|SAF]]'''.

==Design details==
===Operating mechanism===
[[File:SIG SG 543 Right.jpg|thumb|left|SG 543 carbine with stock extended.]]

The SG 540 is an air-cooled, [[Gas-operated reloading|gas-operated]], [[selective fire]] assault rifle that fires from a [[closed bolt]] position. SIG designers used a long-stroke piston-driven action (with the recoil spring wrapped around the piston rod itself) and an adjustable gas regulator with three settings: "0" (used to launch [[rifle grenade]]s), "1" (used in normal operating conditions), and "2" (used in extreme environmental conditions or in the presence of heavy fouling). The firearm is locked into battery by means of a [[rotating bolt]] which features two heavy [[steel]] locking lugs.

The bolt head is rotated by a control cam riding in a helical guide slot machined into the bolt carrier. When a shot is fired, propellant gases from the barrel are fed into the gas cylinder located above the barrel and impart rearward pressure on the piston rod, which drives the bolt carrier back. After a certain amount of free travel built into the system to allow the projectile to depart the barrel, residual gas pressures in the bore drop to a safe level, allowing the breech to be opened. The cam slot in the bolt carrier proceeds to actuate the camming stud in the bolt, rotating the bolt head out of engagement with the locking abutments in the receiver. The spent cartridge casing is extracted by a claw extractor contained in the bolt assembly while a protrusion on one of the internal bolt carrier guide rails in the upper receiver acts as the fixed ejector, removing the casing through a port on the right side of the receiver housing.

===Features===
The rifle is hammer-fired and has a fire control selector mechanism that is also the safety (lever in the "S" position—indicates the gun is safe, "1"—semi-automatic fire, "3"—3-round burst and "20"—fully automatic fire). The SG 540 is fed from either 20 or 30-round staggered box magazines. After the last round is fired, a hold-open tab in the magazine engages the bolt catch that locks the bolt in its rear (open) position. A bolt release button is located on the left side of the receiver.

The [[Rifling|rifled]] barrel is fitted with a [[flash suppressor]], which is also used to attach 22&nbsp;mm spigot-type [[rifle grenade]]s and a [[bayonet]]. The [[iron sight]]s consist of a hooded foresight that can be corrected in elevation and an adjustable (windage only), a rear rotating [[Diopter sight|diopter]] drum that contains four apertures with settings for firing at: 100, 200, 300 and 500 m. The receiver top surface can be used to mount adapters enabling the use of optics.

The SG 540 series come equipped with either a fixed buttstock or a side-folding metal skeleton stock. Another standard feature is a folding lightweight aluminium [[bipod]] that folds into grooves in the lower handguard when not in use. The fixed stock, pistol grip and handguard are all made of high-strength polymers to reduce overall weight. In order to minimize costs, the weapon made extensive use of cost-saving [[Stamping (metalworking)|pressed and stamped steel]] components rather than machined parts.

==Variants==
[[File:SG-540-1M Famae Ejercito de Chile.JPG|thumb|SG 540-1M upgraded by FAMAE in [[Chile]].]]

Differences between the '''SG 542''' and the SG 540 are mainly the result of adopting the more powerful 7.62×51mm cartridge. The SG 542 also uses normally 20/30-round box magazines (5 and 10 magazines were also manufactured) but the sights were modified with a 600 m setting in addition to the 100, 200, 300 and 500 m sight drum positions.

The '''SG 543''' carbine is a shortened variant of the SG 540 that has been modified with a short {{convert|300|mm|abbr=on|1}} barrel, a shorter gas cylinder and piston rod as well as a different handguard and sights with four apertures with settings for firing at 100, 200, 300 and 400 m firing range. The SG 543 lacks the integral bipod of the SG 540/542 and the reduced barrel cannot be used to fire rifle grenades.
The SG 540 served as the basis for the '''SG 541''' prototype, which would later become the [[SIG SG 550|SG 550]] that entered service with the Swiss Armed Forces as the Stgw 90 (''Sturmgewehr 90'').

Additionally, two semi-automatic variants were manufactured by MANURHIN between the late 1970s and the early 1980s specifically for the European civilian market: called the '''SIG Manurhin F.S.A.''' and the '''SIG Manurhin C.S.A.'''. These rifles were chambered in [[.222 Remington]] and [[.243 Winchester]] respectively. Both were available with either 30-round or reduced 5-round magazines, and the option of a folding or fixed stock. The unusual chambering for this type of military-style rifle was an attempt to comply with regulations in certain European countries imposing restrictions on the civilian ownership of "military" cartridges such as the [[5.56×45mm NATO]]/[[.223 Remington]] or [[7.62×51mm NATO]]/[[.308 Winchester]].
[[File:P 20180111 223429 vHDR Auto.jpg|thumb|right|SG 542 Made by FAMAE for the Canadian civilian market]]

==Users==
[[File:SIG SG 540 Users.png|thumb|Map with SIG SG 540 users in blue and former users in red]]<!--READ FIRST: This section is for cited entries only. Please do not add entries into this list without a citation from a reliable source. All entries without a citation will be removed. Thank you.-->
[[File:Ecuadorian Army soldier participates at a UN exercise.jpg|thumb|right|[[Ecuadorian Army]] soldiers equipped with the SG 542, circa 2002.]]

*
*{{flag|Argentina}}:FAMAE SG540-1 and FAMAE SG543-1 issued to federal penitentiary service<ref>{{Cite web |date=2016-11-24 |title=wiw_sa_argentina - worldinventory |url=https://sites.google.com/site/worldinventory/wiw_sa_argentina |access-date=2023-03-07 |archive-url=https://web.archive.org/web/20161124203421/https://sites.google.com/site/worldinventory/wiw_sa_argentina |archive-date=2016-11-24 }}</ref>
*{{flag|Bolivia}}: SG542 issued to the army. SG540-1 issued to special forces.<ref>{{Cite web |date=2016-11-24 |title=wiw_sa_bolivia - worldinventory |url=https://sites.google.com/site/worldinventory/wiw_sa_bolivia |access-date=2023-05-07 |archive-url=https://web.archive.org/web/20161124203425/https://sites.google.com/site/worldinventory/wiw_sa_bolivia |archive-date=2016-11-24 }}</ref>
*{{flag|Burkina Faso}}<ref name="jones2009">Jones, Richard D. Jane's Infantry Weapons 2009/2010. Jane's Information Group; 35 edition (January 27, 2009). {{ISBN|978-0-7106-2869-5}}.</ref>
*{{flag|Cameroon}}<ref name="jones2009"/>
*{{flag|Canada}}  - [[Lethbridge Police Service]]
*{{flag|Central African Republic}}<ref>{{Cite web|url=https://sites.google.com/site/worldinventory/wiw_africa/https-sites-google-com-site-worldinventory-wiw_af_centralafricanrepublic|title = Google Sites}}</ref>
*{{flag|Chad}} - Uses the SG 542 variant.<ref name="jones2009"/>
*{{flag|Chile}} - Uses the SIG-[[FAMAE]] SG 542–1, SG 540 and SG 543 variants. In process of upgrade to M variant.<ref name="jones2009"/> Produced under license by FAMAE.<ref name="modernfirearms">{{cite web |url=http://world.guns.ru/assault/as47-e.htm |title=Modern Firearms - Assault Rifles - SIG SG-540 SG-542 SG-543 |access-date=2007-08-14 |url-status=dead |archive-url=https://web.archive.org/web/20070824065818/http://world.guns.ru/assault/as47-e.htm |archive-date=2007-08-24 }}</ref> Currently in the process of being replaced with the [[IWI Galil ACE]] locally produced.
*{{flag|Côte d'Ivoire}} - SG 540 and SG 543s<ref name="SAS RCI 2012">{{cite report |url=http://www.smallarmssurvey.org/fileadmin/docs/C-Special-reports/SAS-SR14-CoteIvoire.pdf |title=Enquête nationale sur les armes légères et de petit calibre en Côte d'Ivoire: les défis du contrôle des armes et de la lutte contre la violence armée avant la crise post-électorale |last=de Tessières |first=Savannah |date=April 2012 |publisher=[[United Nations Development Programme|UNDP]], Commission Nationale de Lutte contre la Prolifération et la Circulation Illicite des Armes Légères et de Petit Calibre and [[Small Arms Survey]] |pages=74, 97 |language=fr |archive-url=https://web.archive.org/web/20121118234610/http://www.smallarmssurvey.org/fileadmin/docs/C-Special-reports/SAS-SR14-CoteIvoire.pdf |archive-date=November 18, 2012 |url-status=dead |series=Special Report No. 14}}</ref>
*{{flag|Democratic Republic of the Congo}}<ref name="jones2009"/>
*{{flag|Djibouti}}<ref name="jones2009"/>
*{{flag|Ecuador}}<ref name="jones2009"/>
*{{flag|Eswatini}}<ref name="jones2009" />
*{{flag|Gabon}}<ref name="jones2009"/>
*{{flag|Lebanon}}<ref name="jones2009"/>
*{{flag|Mauritius}}<ref name="jones2009"/>
*{{flag|Nicaragua}}<ref name="jones2009"/>
*{{flag|Nigeria}}<ref name="jones2009"/>
*{{flag|Oman}}<ref name="jones2009"/>
*{{flag|Paraguay}}<ref name="jones2009"/>
*{{flag|Senegal}}<ref name="jones2009"/>
*{{flag|Seychelles}}<ref name="jones2009"/>
*{{flag|Syrian Opposition }}<ref name="jones2009"/>
*{{flag|Togo}}<ref name="jones2009"/>

=== Former users ===

* {{flag|France}} - Produced under license by Manurhin and as a temporary resort in limited service used during the late 1970s by the [[French Armed Forces]], [[RAID (French police unit)]] and [[National Police Intervention Groups]].<ref name="modernfirearms" /> Replaced by the [[FAMAS]] in the early 1980s.<ref name="modernfirearms" />
* {{flag|Portugal}} - SG543-1 was used by [[Portuguese army]] [[Commandos (Portugal)|Commandos]] and [[Special Operations Troops Centre]] since 1980s until 2019, when it was replaced by [[FN SCAR]].<ref name="modernfirearms" /><ref>{{Cite web |title=Janes &#124; Latest defence and security news |url=https://www.janes.com/article/86993/fn-herstal-secures-significant-deal-in-portugal}}</ref>

==See also==
*[[SIG SG 510]]
*[[SIG SG 530]]
*[[SIG SG 550]]
*[[SIG Sauer SIG516]]
*[[Gun politics in Switzerland]]
*[[List of assault rifles]]
*[[List of carbines]]

==References==
{{Reflist}}

==Bibliography==
* {{Citation
  | last = Chloupek
  | first = Ireneusz
  | title = Karabiny szturmowe SIG cz. 1
  | pages = 19–23
  | magazine = Nowa Technika Wojskowa
  | location = Warsaw
  | date = October 2002
}}
* Long, Duncan. (1989). ''Assault Pistols, Rifles And Submachine Guns,'' Boulder: Paladin Press
* [https://web.archive.org/web/20070917073711/http://www.sigarms.com/Products/ShowCatalogProductDetails.aspx?categoryid=35&productid=114 sigarms.com]

==External links==
{{Commons category|SIG SG 540}}
*[http://world.guns.ru/assault/switch/sig-540--542--543-e.html Modern Firearms]

{{Swiss Arms}}
{{Kalashnikov rifle}}

{{DEFAULTSORT:Sig Sg 540}}
[[Category:5.56×45mm NATO assault rifles]]
[[Category:Assault rifles of Switzerland]]
[[Category:7.62×51mm NATO battle rifles]]
[[Category:SIG Sauer rifles]]
[[Category:Long stroke piston firearms]]