Sig SG 510 (Sturmgewehr 57), the original Next Generation Squad Weapon?

Why the Stgw. 57 when the rifle (the K31) is fine?


Peers have adopted self loading and fully automatic infantry weapons, the Swiss Military is not able to maintain such a volume of firepower at medium and longer ranges. 

Examples include: the Kalashnikov, the FAL, the CETME/G3, and the M14.


A roller delayed blowback select fire rifle that uses the same ammunition and magazines currently produced, borrowing the best features from our contemporaries while adding a few features of our own: The SIG Sturmgewehr 57. This system streamlines logistics and soldier capability by fulfilling the roles of an infantry rifle, light machine gun, designated marksman rifle, even submachine gun. The Stgw. 57 is the Swiss post-war Next Generation Squad Weapon.

Features of Stgw. 57, development of and reasoning behind these features.


The action is roller delayed blowback with novel replaceable locking shoulders in the frame. Roller delayed blowback was one of the ways this platform handles the recoil of the full size GP11 cartage with select fire. German engineers first developed a roller locking mechanism in the MG42 machine gun, later a ”half lock” mechanism during the late war for in the Gerät 06(H). These German engineers were recruited by the Spanish to develop the roller delay CETME which became the G3. Swiss engineers studied and improved the roller delay concept.

Recoil buffer system

The recoil is absorbed not only with the roller delay bolt but also into a spring-loaded buffer that takes the bolt back into the stock. This system was pioneered the German FG42, the MG42 and others feature a similar buffer system with a shorter spring. The AR-10 borrows the full straight line buffer concept, its first prototype was completed the same year that the Stgw. 57 was adopted. 

Muzzle device

Like the FG42, the muzzle device is ported 360 degrees. Unlike the FG42, the muzzle device has much fewer ports. Less porting is needed since the Stgw. 57’s roller delayed action with straight line recoil buffer distribute the role of recoil mitigation. As a result, the horizontal muzzle emissions of the Stgw. 57 should be more tolerable than FG42 to nearby team members. The roller delay mechanism plays a larger role in recoil reduction inside the gun than the muzzle device does on the outside, the impulse of the Stgw. 57 is rather “clunky”. 


Stgw. 57 borrows the GP11 cartridge from the K31 bolt action it replaced, the manufacture of the cartridge was maintained at full production without any changes. GP11 performs almost identical to the 7,62 NATO, firearms in 7,62 NATO which were adopted around same time as the Stgw. 57 were the FAL, CETME/G3, M14, and AR-10


The magazine is borrowed from the Swiss LMG 25 (light machine rifle of 1925), why reinvent the wheel when there is a magazine in the arsenals that works perfectly with the same calibre? The Stgw. 57 adds a Kalashnikov style magazine release to facilitate magazine changing.


As a consequence of the straight line recoil system, the sights must be placed higher above the bore than on a traditional rifle. The sights are similar to other predecessors and contemporaries with straight line recoil systems: FG42, Johnson 1941 LMG and AR-10. Like the FG42 (and for some unknown reason only the rear sight of the Johnson 1941 LMG) the sights flip down to prevent being snagged during transportation.

Forward grip and heat shield

The front grip is quite small and close to the action, a common design during around this time. The FG42 and Johnson 1941 LMG feature quite similar grip desgins. The K31 has grip handles inletted close to the action as well, the long wooden forestock on the K31 is actually designed to protect the freeloading barrel underneath rather than provide a long grip.

The heat shield on the Stgw. 57 would protect the hands a bit in the unlikely event they slipped from the grip, what they really do is distribute heat away from the barrel to decrease cooling time. The MG42 features a similar heat shield, touching it during and after firing is a really bad idea.


The Johnson LMG comes from the factory with a bipod pointing forward from the short foregrip, the FG42 comes with a bipod pointing backwards from near the muzzle. The Stgw. 57’s bipod is the best of both worlds, it is unique because it can switch between front and rear positions at the operations discretion. The bipod has distance markings to assist in launching rifle grenades. Like other bipods of the time, it is not adjustable (nor would it need to be).


The trigger is not too heavy to be inconvenient and not too light to discharge by surprise when creeping up on it. Current Swiss legal code prohibits ”hair triggers” and they have never been part of their military doctrine. The platform comes factory with a fold out winter trigger: to fire in subzero Alpine climate, of course.

The winter trigger comes from the factory on all Stgw. 57s, it simply folds out.

Sporting adaptation.

Like every Swiss military rifle, it must be used for the 300 meter target competition discipline. The Stgw. 57 is an excellent target rifle; the barrel is free floating and the self-loading capability allows the shooter to better focus on the task at hand. It can be expediently adapted for globe diopter sights. An adjustable bipod is another simple adaption; unlike the military rifle, one size does not have to fit all. 

The factory PE57 (semi auto version of the Stgw. 57) and a version upgraded for match target use. (top and bottom, respectively)
Rear diopter and front globe sight. (left and right, respectively)
Sight picture of front globe through rear diopter. To aim, simply centre the globe with the rear diopter circle. The rear diopter has multiple colour filter options for shooting in different conditions.
Adjustable bipod legs.

Timeline of predecessors and relevant contemporaries. Suggestions for further research on self-loading rifles.

1908 Mondragón rifle developed by SIG in Neuhausen am Rheinfall with the help of Colonel Schmidt. One of the very first self-loading military rifles, about 4000 were built. It was adopted by the Mexican Army during the rule of Porfirio Díaz and later the German Empire. It fires a full-size 7mm Mauser cartridge, it worked well in trials but didn’t load reliably with non-factory ammunition.

1925 Swiss LMG 25 Light Machine Gun adopted for designated squad gunners. GP11 calibre and magazine were borrowed by its replacement, the Stgw. 57.

1931 Swiss K31 bolt action infantry rifle is adopted as the main infantry rifle, GP11 calibre and charging handle are borrowed by its replacement, the Stgw. 57.

The M1 Garand enters American service, it serves as the primary US infantry rifle until it is replaced by the M14 in 1957. Contemporary self-loads a full-size rifle cartridge from a fixed magazine, using an en bloc clip. Some are later fitted with winter triggers (in the Korean War, for example).

1942 MG42 enters German service as their newest general purpose machine gun, it was a streamlined MG34. Both the MG34 and MG42 were heavily proliferated, every infantry squad had one. The roller lock action will later be adapted into roller delayed blowback. The MG34 and 42 feature a straight line recoil buffer and heatshield. Some featured a winter trigger.

FG42 enters German service as a multi role paratrooper squad weapon, it fires full size rifle cartridge with select fire from box magazines. It features a straight line recoil buffer, raised sights, short front handgrip, recoil reducing muzzle device, and front mounted bipod. It was only produced in limited numbers, but it was a major inspiration in the design of the Stgw. 57. The FG42 was likely the first multi-role squad weapon fielded: it functioned as an infantry rifle, designated marksman rifle, and machine gun all in one.

1941 American Johnson light machine gun enters US service in limited numbers. It features a straight line recoil system, raised sights, a short front handgrip, rear mounted bipod, and fires a full size rifle cartridge from box magazines.

The Swiss begin working on the adoption of a self loading infantry rifle or “Next Generation Squad Weapon” for their military around this time, in response to the proliferation of self loading rifles by their peers.

1940-45. German MKb42/MP43/MP44/Sturmgewehr44 select fire carbine “storm rifles” are developing and serving. First design lineage to self-load intermediate cartridges with select fire. They feed from box magazines and use a straight line recoil buffer. This design was intended to serve in a new class as an automatic infantry rifle, overwhelming the enemy with a high volume firepower while maintaining unpresented mobility. Over 400,000 of the “storm rifles” were produced, they inspired the wave of intermediate cartridge self-loading “assault rifles” that followed.

1945 SKS (Simonov’s Carbine) adopted for Soviet military service and began production in 1949, contemporary self loads an intermediate cartridge from a fixed magazine. Cheap to manufacture. Production of Kalashnikov’s rifle quickly outpaced the SKS, the proliferation of the SKS in the Soviet military paled in comparison.

1945-195? Gerät 06(Halbstarr), also known as Sturmgewehr 45(M), was designed by Mauser engineers. It featured the very first “half lock” or roller delayed blowback system, a further development of the original Sturmgewehr. The roller lock system is attributed to Dr. Karl Maier and Dr. Ludwig Vorgrimmler, they were both captured at war’s end. This firearm was not quite complete at the end of the war, all production materials were shipped by rail to the Austrian Alps but it is unclear which nation captured them. Fully assembled versions of the Gerät 06(H) design exist, the location of their final assembly is unclear. Vorgrimmler (and possibly Maier) had been hired by French Mulhouse Study and Armament Centre to work on this design, it is known that at least two iterations of this design were developed in France (one in 1949 and 1950).

1946 SK46 Swiss self loading semi-auto rifle designed but never adopted. Visually similar to K31 bolt action, they used same ammunition and magazines.

1946-1953 FAL prototypes were designed, and production began in this period. Contemporary self loads (often with select fire) the full size 7,62 NATO cartridge from a box magazine. It uses a short stoke spring dampened gas piston to operate a rotating bolt. The FAL has a rougher impulse than anything using roller delay but was cheap to manufacture. The FAL and its offshoots became the most successful and proliferated battle rifle (full-size self-loader) of all time. It was used by the United Kingdom, Ireland, Malta, Netherlands, Belgium, Austria, Croatia, Serbia, Montenegro, and a plethora of non-European countries. Often referred to as the “Right arm of the free world”.

1947 Observation of Kalashnikov beings in Soviet military trials, it entered production in 1948. Contemporary self loads an intermediate cartridge from a removeable box magazine with select fire, uses a rotating bolt and long stroke piston. Manufacture is cheap and streamlined. The rifle and its offshoots are proliferated to state and non-state actors across the world over time. This design is one of the most consequential in history, the Kalashnikov platform is more often present than absent in conflicts of the last 50 years. It estimated that over 100 million Kalashnikov type rifles have been produced.

1952-1958 Heckler & Koch G3 development began with the CETME rifles in Spain (CETME standing for the Centre for Technical Studies of Special Materials). Dr. Ludwig Vorgrimmler was one of the German engineers were hired by the Spanish government for this project (after he left France). Roller delayed blowback was the crux of the design, the major development at CETME from the Vorgrimmler’s Gerät 06(H) was the adaptation for a full-size cartridge. Heckler Koch purchased the rights from Spain to use their developments for what would become the contemporary HK G3, the Spanish would continue production of their own design. The CETME and G3 were implemented by the Spanish and German forces throughout the cold war, respectively.

1953 AK53 Swiss prototype self-loading select fire rifle was completed as an attempt at becoming their next generation squad weapon. It used a novel “blow forward” operating mechanism, the barrel was pushed forward by ported off gas and then fell backwards to chamber the next cartridge. To chamber the first round, the charging handle was pushed forward to manipulate the barrel. The platform used the GP11 cartridge and modified LMG 25 magazines. The system was never adopted or exported, ultimately a failure.

1955 Swiss SIG MG 710-1 prototype is completed, an MG42 adapted from roller lock to roller delay. This is an important step in the Swiss’ development of roller delay for a full-size rifle cartridge, taking place separately from the development of the HK G3. This was not adopted by Switzerland, but the linage had moderate commercial export sucess.

AM55 was the predecessor to the Stgw. 57 and it was nearly functionally identical, the minor differences mostly pertained to materials. It was approved by Swiss military trials to be adapted into their new squad weapon. The AM55 is distinguishable by its use of wood furniture, but it is easily confusable with later offshoots of the SG 510 made for export.

1954-1957 The M14 is adapted from the M1 Garand and adopted by US military as a multi role squad weapon, it compromises in every role. Contemporary self-loads the 7,62 NATO rifle cartridge from a removeable box magazine with select fire. It was short lived, replaced in 1962 by a smaller intermediate cartridge version of the AR-10.

1955-1956 AR-10 was designed. Contemporary self loads 7,62 NATO from a box magazine with select fire. Features straight line buffer recoil system and raised sights, some had an FG42 like ported compensator. Minor commercial export success, pales in comparison to model 15 intermediate carbine descendant (the ubiquitous AR-15).

1957 Stgw. 57 is adopted by the Swiss military as their next generation squad weapon.


Roller locked action, half lock action: Rear spring pushes bolt forwards and rollers push out to lock bolt closed; rollers unlock under blowback pressure.

Roller delayed action: Bolt carrier and locking piece must recoil backwards under blowback pressure first in order for the rollers to unlock, unlock is delayed.

“Roller-delayed blowback-operated breech for automatic weapons” by Thuringius is licensed under GNU Free Documentation License

Rotating bolt action: The locking lugs are rotated into recesses in the frame or barrel extension to lock the cartridge into the bolt. Could refer the action of a manual action or self-loading firearm.

Full-size, rifle cartridge: Common large cartridge used for bolt action rifles and machine guns. Sometimes designed to be fired up to 2000 meters.

Intermediate: A cartridge that is smaller overall than a traditional rifle cartridge, greater range and longer than a pistol cartridge. Lower recoil, lower weight, and offering a higher volume of fire than traditional rifles. Reduced range than a full-size cartridge, up to 1000 meters.

Squad weapon: Mutli-role firearm for use in a squad.

Self-loading: Automatically loads cartridges as opposed to manually loading, not necessarily fully automatic.

Select fire: Capability of fully automatic fire, selectable between semi automatically and fully automatic.

Carbine: Smaller and shorter rifle. It can be built in full size or intermediate calibers.

Light Machine Gun: Type of machine gun intended to be more mobile than a fixed machine gun.