World War 2 (1939-1945) showcased the value of self-loading rifles for the various armies participating in the grand conflict. This worldwide exposure then led to a vast market for such types in the decades following and the SIG concern of Switzerland responded with several designs during the period - among them becoming the "SG 510" Battle Rifle which was, essentially, the NATO-caliber form of the earlier Stgw 57 series (this post-war model chambered for 7.5x54mm Swiss M1911).
The Battle Rifle category was born out of the post-war need to differentiate self-loading rifle types from their Assault Rifle cousins. The former fired full-powered rifle cartridges from a semi-/full- automatic action while the latter followed suite but instead chambered an intermediate cartridge (the Colt M16 in 5.56mm for example). As such, those long guns appearing in the immediate post-war years, such as the American Springfield M14 and Belgian FN FAL, became recognized as "battle rifles".
The SG 510 followed in line with the stated battle rifle characteristics: it chambered the 7.62x51mm NATO rifle cartridge, which was seeing widespread adoption in the West (since 1954), and operated from a an automatic action - this directed by a roller-delayed blowback system of operation. It fed from a 20-, 24-, or 30-round detachable box magazine and reached ranges of up to 700 yards using the standard iron sights. Optics increased this out to 875 yards. Rate-of-fire was 450 to 600 rounds-per-minute. The weapon weighed 9.6lb, showcased a length of 43", and utilized a barrel measuring 19.9" long.
Externally, the rifle followed a traditional design arrangement that included a shoulder stock, pistol grip, and mostly-shrouded barrel assembly. The barrel was capped at the muzzle by a perforated brake. The charging handle was set to the right side of the receiver and primarily managed by the right hand. The magazines were inserted into a well ahead of the trigger unit. The forward and rearward iron sights were very noticeable due to their height and located at the end of the handguard and at the rear upper section of the receiver, respectively.
Design attribution of the SG 510 was given to Rudolf Amsler and much of this work was conducted during the early 1950s. Production ramped up in 1957 and spanned into 1983 while primary variants of the base design included the SG 510-1, SG 510-2, and SG 510-4.
The SG 510-1 marked the original, standard battle rifle adopted by the Swiss Army and the SG 510-2 was a lightweight form of the same gun. The SG 510-3 was showcased with a shortened barrel assembly and intended for the Finnish Army but was ultimately rejected in its prototype form. The SG 510-4 was also given a short barrel but its rubberized shoulder stock was now converted to one of wood construction with new design lines - both Bolivia and Chile accepted this model into service. The SG 510-5 was chambered for the 7.62x63-US 30-06 rifle cartridge, intended for Mexico, but rejected in its prototype form. The SG 510-6 was restricted to testing and chambered the local Swiss 7.5x55 cartridge. The AMT ("American Match Target") , based on the SG 510-4, was marketed to the United States as a precision product for civilian use but manufacture was limited (.308 chambering). The SG 510-6 became another prototyped model, this in 7.5x55mm, and intended to supersede the Stgw 57 line. The PE 57 existed for the civilian market and thusly restricted to semi-automatic-rifle-only while chambered for 7.5x55mm GP11 Swiss.