Stgw. 57 / Sig 510 assault rifle (Switzerland)

7.5mm SIG Stgw.57assault rifle as used by Swiss army, right side, with bipod attached to forward position

7.5mmSIG Stgw.57 assault rifle as used by Swiss army, left side, with foldedbipod attached to rearward position

Semi-experimental 7.62x39SIG 510-3 assault rifle as made for Finnish army assault rifle trialsin late 1950s

7.62x51 NATO SIG 510-4assault rifle, as made for export

7.62x51 NATO SIG AMTsemi-automatic rifle, as made for civilian sales

Caliber:7.5x55 mm GP11 (Stgw.57) or7.62x51mm NATO (SIG 510-4)

Action: roller retarded blowback

Overalllength: 1105 mm (1016 mm SIG 510-4)

Barrel length: 583 mm (505 mm SIG 510-4)

Weigth: 5.56 kg empty (4.25 rg empty SIG 510-4)

Magazine capacity: 24 rds (20 rds SIG 510-4)

Switzerland began to experiment with intermediate cartridges before the World War 2 and, being a neutralcountry, closely watched the developments made during and after the war. Being entirely satisfied with the power and accuracy of its 7.5 mmGP11 (7.5x55) cartridge, the Swiss army tried to achieve a full power selective-fire rifle. After a couple of false starts, first with the gas-operated Sk-46 self-loading rifle, and secondly with the most unusual AK-53 blow-forward design, the famous SIG company finally produced a weapon which satisfied the Army in 1955.

This was the 7.5 mm AM-55, a retarded blowback design, developed under the leadership of the Rudolf Amsler. The basic principles of the action were borrowed from German WW2 period Mauser 'Gerät 06H' and Stg.45(M)assault rifles, but with much altering involved. In 1957 the Swiss army adopted the AM-55 as the Schturmgewehr-57, or Stgw.57 for short. Madebetween 1957 and 1983, the Stgw.57 represented one of the finest and most expensive automatic rifles ever issued to any army in the world.Chambered for full power 7.5 x 55 GP11 ammunition, the Stgw.57 provides long range accurate shooting in semi-automatic mode, necessary for thetypical Swiss mountain country, in combination with significant fullauto firepower, thanks to its relatively heavy weight, integral bipodand a shrouded barrel. In the modified form, known as the SIG-510, this design was relatively successful, being sold to various South Americancountries, most notably Bolivia and Chile, chambered for 7.62 mm NATO ammunition.

The action of the Stgw.57 was derived from the roller-retarded blowback system originated by Mauser engineers in Hitler’s’ Germany. However, the Swiss designers replaced the roller swith the roller-shaped pivoting flaps, interposed between the bolt head and the bolt body. The receiver is made from stamped steel, with a separate trigger unit housing made integral with the pistol grip frame and trigger guard. The fixed barrel has a perforated steel jacket with two mounting points for an integral bipod – one near the muzzle, and another near the receiver. The front part of the barrel is exposed to act as a rifle grenade launcher. To smooth out the excessive recoilgenerated in full automatic fire, and especially by rifle grenades, thefixed butt-stock is fitted with a recoil buffer. The safety / fire mode selector is located at the left side of the trigger unit. Stgw.57 isfitted with large, T-shaped charging handle and with the folding“winter trigger”, which, when unfolded, extends down below the triggerguard, enabling the rifle to be used in arctic mittens. Since theStgw.57 was designed with the so-called straight-line layout, theraised sights are mounted on high, folding bases, with the rear sight being micrometer-adjustable from 100 to 650 metres. The Stgw.57 also could be fitted with the special Kern 4X telescope sight. Stgw.57 is fed from curved box magazines, made from steel and containing 24rounds. The small forend is made from plastic and the gun is fitted with a side-folding carrying handle. Other accessories include the sling, the bayonet, and a special small-capacity magazine for blankgrenade-launching cartridges.

Export military versions of the Stgw.57, known as SIG SG-510, were made in 4 basic modifications, of which only one was made in any significant quantities, the SG-510-4.This was chambered in 7.62 x 51 NATO, had a shorter barrel, and non-folding aperture sights. The forend and buttstock were made from wood.

Other versions included the SG-510-1 (exactly the samerifle as the Stgw.57), the SG-510-2 (a lightweight modification of theStgw.57, also in 7.5 mm), and the more compact SG-510-3, chambered forthe Soviet 7.62 x 39 cartridge (produced in late 1950s for assault rifle trials in Finland). Civilian semi-automatic only versions of the Stgw.57 were designated as PE-57 (in 7.5 mm GP11) and SIG AMT (a semi-auto version of SG-510-4 in 7.62 mm NATO).

SIG SG-540 SG-542 SG-543 assault rifles (Switzerland)

5.56mm SIG SG-540 assault rifle, with fixed butt and optional bipod

5.56mm SIG-Manurhin SG-540 assault rifle as made in France under license, with side-folding butt

7.62mm SIG SG-542 assault rifle, with fixed butt

5.56mm SIG SG-543 short assault rifle, with side-folding butt

The SIG SG-540 had been developed by the Swiss company SIG in the mid-1970s as a new,lightweight assault rifle, chambered in then-new small-caliber ammunition (.223 Rem / 5.56mm NATO). The SG-540 was licensed to the Manurhin of France and FAMAE of Chile, and had been temporarily used by FrenchArmy (who replaced it with FA MAS rifle in the early 1980s), Portuguese Army and Chilean army, and some other countries, mostly in South America and Africa. 7.62mm NATO version also had been developed, butfound no significant sales. The SG-540 itself had not been adopted by Swiss military, but it became the platform for further improvements,which lead to the SIG-550 / Stgw.90assault rifle. SG-540 currently is in production only by FAMAE company of Chile.

Early SIG prototypes, chambered in 5.56mm ammunition and known as SIG SG-530, were using some forms of roller locking, and thus, were too complicated and expensive to make. To made the rifle as cheap and reliable as possible, SIG designers selected the AK-47 style action,gas operated, with gas piston attached to the bolt carrier, and with rotating bolt with two massive lugs. The recoil spring is located around the gas piston rod, and the bolt carrier attached to the gaspiston rod by the removable charging handle. The gas port has gas regulator with two different open and one closed position (latter for firing rifle grenades). The receiver is made from stamped steel and hastwo major parts, upper and lower, which are connected by pushpins. The barrel is screwed into the upper receiver. The trigger unit has a safety/fire selector switch on the left side of the receiver, with 3 settings: safe, semi-auto, full-auto. If desired, additional modulecould be installed in the trigger mechanism to allow 3-rounds burstmode. Rear sights are drum-type (like those found on Heckler-Kochrifles). SG-540 has muzzle compensator/flash hider of NATO-standard diameter, so it is possible to launch rifle grenades from the muzzle.The SG-540 has integral folding bipods under the handguard, and can be issued with fixed plastic buttstock or with side-folding tubularmetallic buttstock.

The carbine version of the SG-540 is called SG-543 and has shorter barrel. SG-543 can't fire rifle grenades. 7.62mm version of SG-540 is known as SG-542 and visually differs mostly by rectangular magazine of greater depth. SG-542 is chambered for 7.62x51mm NATO ammunition. The civilian version of the SG-540 can fire only in-semi-auto and can be chambered also for .222 Remington cartridge. Other chamberings such as 7.62x39mm Russian (for SG 540) and.243Winchester (for SG 542) are possible but extremely rare.

SIG SG-550 SG-551 SG-552 Stgw.90 assault rifles (Switzerland)

Complete family of SIG55x rifles, top to bottom: SIG SG 550 / Stgw.90, SIG SG 551-LB SWAT,SIG SG 551 and SIG SG 552 SWAT

SIG SG 550 / Stgw.90 assaultrifle, left side view

In the late 1970s the Swiss army began the search for a new, smaller caliber rifle to replace old,full-power 7.5mm Stgw.57 (SIG510)automatic rifle. Initial tests were done with the 5.6 x48 Eiger and 6.5 x 48 GP80 ammunition. Prototype rifles were developed by SIG (based on their SG-540 design) and by the state-owned Waffenfabrik Bern (W+F). However, the Swiss army selected a slightly improved version of the 5.56 x 45 NATO cartridge as the 5.6 mm GP90, and further testing proved the superiority of the SIG SG-541 rifle over its W+F rival. In 1983, the Swiss Army officially adopted the SIG SG-541 as the Sturmgewehr-90, orStgw.90 although due to financial reasons production began only in 1986. Currently, the Stgw.90 is a standard Swiss service rifle.

The Swiss army took its last deliveries of the Stgw.90 in the mid-1990s, but these rifles are still offered for ex port by the international SIGARMS organization, as well as sold for the civilian market in semi-automatic only versions. In export form this rifle is known as the SIG SG-550. "Carbine" and subcompact"Commando" assault rifle versions are available in the form of SIGSG-551 and SIG SG-552, respectively. Civilian versions of the SIGSG-550 and 551 are known as the Stgw.90 PE in Switzerland or SIG 550-SPand 551-SP when sold for export.

The SIG-550 is often referred as the finest 5.56 mm rifle ever made. It is also, not surprisingly,quite expensive.

Recently, SIG Arms has introduced a civilian/ law-enforcement offspring of the SG-550, known as SIG 556. This is asemi-automatic rifle, altered to accept M16-type magazines and fitted with "Americanized" furniture.

Basically, the SIG-550 is a somewhat lightened and refined SIG SG-540/541 rifle.SIG SG-550 is gas operated, with gas pistonremovably attached to the bolt carrier, and with rotating bolt with two massive lugs. The recoil spring is located around the gas piston rod, above thebarrel, and the bolt carrier attached to the gas piston rod by the mean of removable charging handle. The most compact weapon in the line, theSIG SG-552, is similar to SIG SG-551 but it has even shorter hand guard and barrel. Due to short barrel and gas piston,SG-552 has return spring relocated to the rear part of the receiver,and thus it has an altered bolt carrier and upper receiver. The gas port has gas regulator with two different open and one closed position (latter for firing rifle grenades). The receiver of all SG-55x series guns is made from stamped steel and has two majorparts, upper and lower, which are connected by push pins. The barrel is screwed into the upper receiver. The trigger unit has a safety/fireselector switch on the left side of the receiver, with 3 settings:safe, semi-auto, full-auto. If desired, additional module could be installed in the trigger mechanism to allow 3-rounds burst mode. Rearsights are drum-type (like those found on Heckler-Koch rifles). On certain current production models rear sight is replaced with full-length Picatinny style rail with folding back-up reat sight. SIGSG-550has muzzle compensator/flash hider of NATO-standard diameter, so it is possible to launch rifle grenades from the muzzle. The SIG-550 can befitted with detachable folding bipods under the handguard, and is issued with side-folding, skeletonized polymer buttstock. Every rifle of SIG SG-550 family can be fitted with proprietary, quick detachable scope mount,although current production rifles are usually fitted with one or more picatinny rails.Swiss Stgw.90 are often seen with 4X fixed power scope, export versions can be equipped with commercial telescope sights, ACOG or "red dot"sights, depending on customer preferences. SIG SG-550 also can befittedwith bayonet. Standard magazine capacity for Swiss military Stgw.90 rifles is 20 rounds, as Swiss tactical doctrine calls for accurate semi-automatic fire, reserving full automatic mode only for emergency purposes. Standard magazines can be clamped together for ease of carry,using integral studs on the magazine walls. For those who might require more firepower, SIG also produces 30-round magazines.

The carbine version of the SIG-550 is called SG-551and has shorter barrel. Quite recently, SIG also introduced a "long barrel" version of the SG-551, which is known as SIG SG-551LB. SIG-551can't fire rifle grenades.

SIG SG 750 and SG 751 SAPR rifle (Switzerland)

Military / LE select-fire SIG SG 751 LB SAPR rifle

Military / LE select-fire SIG SG 751 SB SAPR rifle, with shoulder stock folded

Civilian semi-automatic only SIG SG 751 LB SAPR rifle

The SIG SAPR (Semi-Automatic Precision Rifle) was first announced in 2004 by the Swiss-based branch of the international SIG-Sauer arms making company, and, apparently, entered initial production in Switzerland in 2009. Over the development years the SIG SAPR system evolved into two branches - one retained semi-automatic mode of fire and is intended for civilian and law enforcement markets; another is a select-fire battle / assault rifle, which is intended for Military and special Law Enforcement applications only. The SIG SG 751 SAPR rifles are based on the time-proven 5.56mm SIG SG 550 / Stgw.90 family of rifles, with major elements of the action necessarily enlarged and strengthened to handle bigger and more powerful 7.62 NATO / .308 Win ammunition. At the present time, SIG SG 751 SAPR rifles are offered in two military versions (SB - short-barreled and LB-Long Barreled). Civilian versions may have different barrel lengths (currently advertised civilian-legal versions have barrels 455 or 570 mm long) and, obviously, cannot fire in full automatic or burst modes.

The SIG SG 751 SAPR rifle is gas operated, with gas piston removably attached to the bolt carrier, and with rotating bolt with two massive lugs. The recoil spring is located around the gas piston rod, above the barrel, and the bolt carrier is attached to the gas piston rod by the mean of removable charging handle. The gas block is equipped with manual gas regulator with four positions (normal operations / adverse conditions / for use with silencer / shut-off, manual reload). The receiver of the SIG SG 751 SAPR rifle is assembled from two parts - stamped steel upper and aluminum alloy lower, connected by the captive push-pins. The controls are ambidextrous, and in MIL / LE versions the combined safety / selector lever has 4 positions - for Safe, Single shots, 3-round bursts and Full-automatic fire. In civilian-legal versions this lever has only 2 positions - for Safe and Fire. Feed is from proprietary 20-round detachable box magazines, made of plastic. Cold-hammer forged barrel can be easily replaced if needed. Barrel is free-floated for maximum accuracy. The sighting equipment is installed on the integral Picatinny rail on the top of the receiver, and normally SIG SG 751 SAPR rifle is provided with back-up iron sights, consisting of folding front sight and drum-type diopter rear sight. The polymer side-folding stock is same as used on the5.56mm SIG SG 550 / Stgw.90 rifles.