SIG PE57 and AMT

THE SIG StG 57 (PE57) and SIG 510 (AMT)

The 7.5-mm StG 57 (PE57) assault rifle is the standard Swiss Army rifle. This weapon, developed by the Swiss SIG Company, is also known as the SIG AMT when chambered for the 7.62mm NATO cartridge. A small quantity of these rifles also were produced by Beretta in Italy and sold in South America. There is little military use of this rifle except by the Swiss Army; however, the SIG 510′s (AMT) are offered for commercial sales in both selective-fire and in semiautomatic fire models. The PE 57 is easily identified by Its angular, ungraceful appearance; long, perforated tubular barrel jacket; folding sights; small plastic forearm: and plastic butt. Also, the Swiss cross is stamped over its chamber. The commercial SIG AMT’s are similar to the StG 57 but can be identified by their larger wood forearm and slimmer look.

Both the PE57 and AMT are a delay blowback-operated, detachable box magazine-fed, semi auto only weapon. These rifles often are equipped with a folding metal bipod , a foldaway winter trigger , and a loaded-chamber indicator.

The PE 57 and SIG AMT function identically, and are both delay blowback operated. When the trigger is pressed, the hammer is released to strike the firing pin lever and fire the cartridge. The pressure generated during firing drives the cartridge case rearward, and the case, in turn, attempts to drive the bolt rearward. The rearward movement of the bolt is, however, delayed because the two rounded locks are seated in recesses in the receiver and held there by the cam nose of the bolt carrier. The rearward thrust of the bolt causes the locks to attempt to cam out of their recesses and as they do, their pressure against the cam nose of the bolt carrier forces the heavy carrier rearward. The delay caused by the locks coming out of their seats and forcing the heavy carrier rearward allows sufficient time for the bullet to leave the barrel for the gas pressure to fall to a safe level.

The bolt carrier, however, has been given sufficient momentum to travel fully to the rear. As it does, it compresses the driving spring and rocks the hammer rearward. The extractor pulls the fired cartridge case out of the chamber and holds it to the bolt face. As the bolt nears the end of its travel, the ejector strikes a cam surface in the receiver and suddenly pivots on its pin. This throws the fired case out through the ejection port. The bolt strikes the forward end of the butt stock and stops; the compressed driving spring then drives the bolt forward. The feed rib drives the top cartridge out of the magazine and into the barrel. As the bolt nears the end of its forward travel, the carrier cam nose forces the locks out into their recesses, and the extractor engages the rim of the cartridge. The bolt strikes the barrel, the carrier strikes the bolt, and forward movement ceases. The hammer, when released, is driven by its spring and strikes the end of the firing pin lever. This lever pivots on its pin and drives the firing pin forward to strike the cartridge primer.

The loaded chamber indicator is a small spring-loaded plunger that fits into the top rear end of the barrel. Normally the indicator is flush with the top of the receiver, but when the cartridge is chambered, the rear of the cartridge forces the indicator up, above the top surface of the receiver. The projecting indicator thus signifies that there is a cartridge in the chamber. There is no last-round catch on the rifle.

The bayonet is affixed by placing its ring over the muzzle while fitting the butt onto the bayonet stud until the bayonet locks in place. Remove the bayonet by pressing the large round catch on the butt and pull it forward off the rifle.

The cleaning kit consists of a weight and string pull-through with a bristle brush and a small clip to keep the chamber indicator out of the chamber. To use the clip, reach into the chamber and press the indicator; when it protrudes, slip the clip onto the groove in the indicator. The cleaning kit and night sights are carried in the pistol grip. To obtain them, insert the point of a bullet into the hole in the plate over the bottom of the pistol grip to slide the plate open.