In 1978, the Swiss armed forces formulated requirements for a successor to the Stgw 57 battle rifle (known commercially as the SG 510) using the 7.5×55mm GP 11 cartridge.

Production began in 1986 and four years later the rifle was officially accepted into service in 1990, hence the military designation Stgw 90.

It has a gas-actuated piston-driven long-stroke operating system derived from the SIG SG 540 series of rifles, which uses burnt powder gases vented through a port in the barrel to power the weapon's moving parts.

A spring-loaded extractor is incorporated into the bolt while a fixed protrusion on one of the receiver's internal guide rails ejects the spent cartridge casings.

The magazines are molded from a translucent polymer and can be locked together using studs in order to facilitate quicker reloading (Jungle style).

Alternatively, a left-handed shooter may release the bolt by pulling the rubber-coated charging handle to rear a short distance.

The stock, pistol grip, and handguards are made of a high-strength polymer, and are produced in either green or black colour options.

[4] The heavy, cold hammer-forged barrel is screwed into the receiver and is equipped with a slotted "bird cage" type flash suppressor that is also used to launch rifle grenades (using standard, live ammunition) or attach a knife bayonet (the bayonet is supported by a lug located at the base of the gas block).

The sights consist of a rear, rotating diopter drum soldered to the receiver and a hooded front post installed in the gas block.

The sights are adjustable via micrometer screws with windage and elevation increments of 0.15 mil (≈0.52 moa), or 15 mm (0.6 in) at 100 m. For night use, the dedicated "1" notch setting in the rear sight drum is provided with two self-luminous tritium-powered inserts fitted laterally on each side of the notch and additionally in a flip-up post attached to the foresight.

[citation needed] The sight weighs 730 g (26 oz) and includes a variety of features, such as STANAG 2324/MIL-STD-1913 compliant mounting components, a Bullet Drop Compensation (BDC) elevation adjustment knob for ranges from 100 to 600 m, a tritium-illuminated reticle that enables target acquisition in low-light conditions and a diopter eyesight correction adjustment.

Included with the sight is a lens hood for mounting on the ocular that reduces image quality-impairing stray light and a gray filter for glare reduction.

Swiss Arms (respectively Brügger & Thomet) offer several types of quick-release scope mounts and Picatinny rails.

The grenade launcher is a single-shot breech-loaded weapon that is supplied with a leaf sight that attaches to the rifle's rear sight base and enables accurate firing out to 200 m. The lightweight aluminium launcher weighs 1.7 kg (3.7 lb) unloaded, and is operated independently of the rifle.

It can use a wide array of 40×46mm grenades, including extended range high-pressure types and non-lethal baton or anti-riot projectiles.

With a proper lug adaptor, the rifle will also accept a NATO-pattern KCB-77 (made originally by Carl Eickhorn of Solingen, West Germany) or the American M9.

It has a shorter 226 mm (8.9 in) barrel (with an open, 3-prong flash suppressor) and gas tube, ventilated handguards and a redesigned bolt carrier group that was integrated with the piston rod to form a single moving assembly.

Further factory options for the SG 553 rifle series are an integrated receiver Picatinny rail and an adjustable butt stock.

The modifications are available as a conversion kit that includes a new bolt carrier, charging handle, recoil spring and gas tube.

[14] Introduced in 1988, This accurized rifle has a refined two-stage trigger (the pull force was reduced from 35 N (7.9 lbf) to 15 N (3.4 lbf), a heavy, hammer-forged 650 mm (25.6 in) long barrel with a 254 mm (1:10 in) rifling twist rate (it has no flash hider) and is used exclusively with telescopic sights.

The ordinance GP 90 ammunition is optimized for use with the original Swiss 254 mm (1:10 in) rifling twist rate.

Due to import restrictions, the American civilian market required a partially American-made version assembled by SIG Sauer, Inc. in Exeter, New Hampshire.

[20] On 27 February 2014, the Canadian semi-automatic "Classic Green" sporting rifle, also known as the "Swiss Arms PE 90", was re-classified as a "prohibited weapon".

This caused outrage amongst owners and lobbyists, who felt that the RCMP exceeded their authority, and that such policy changes should be enacted by legislation.

[citation needed] The National Firearms Association of Canada considered pursuit of the matter through the legal system.

[22] On 31 July 2015, the Canadian government overturned the reclassification and returned the Swiss rifles to the original classifications.