CETME Model 58

CETME Model C
CETME Model C with wood stocks
Type	Battle rifle
Place of origin	Spain
Service history
Used by	Spanish Army
Production history
Designer	Ludwig Vorgrimler
Manufacturer	Centro de Estudios Tecnicos de Materiales Especiales (CETME)
Specifications
Weight	9.9 lb (4.49 kg)
Length	40 in (1,016 mm)
Barrel length	17.7 in (450 mm)
Cartridge	7.62×51mm NATO
Action	Roller-locked delayed blowback
Rate of fire	Full-auto: 550-650 rounds per minute
Muzzle velocity	2580 ft/sec
Feed system	20-round detachable box magazine
Sights	Iron sights

The CETME Model 58, is a stamped-steel, select-fire battle rifle produced by the Spanish armaments manufacturer Centro de Estudios Tecnicos de Materiales Especiales (CETME). The Model 58 used a 20-round box magazine and was chambered for the 7.62×51mm NATO round (although originally designed for the reduced power Spanish 7.62×51mm cartridge). The CETME 58 would become the foundation of the widely deployed German Heckler & Koch G3 battle rifle. Semi-automatic variants were also produced for the civilian market.

The CETME (Centro de Estudios Tecnicos de Materiales Especiales) rifle was designed primarily by the German engineer Ludwig Vorgrimler, who based his design on the experimental German StG 45(M) and the French-made AME 49. The StG45 used a roller-delayed blowback mechanism somewhat similar to the roller-locking system patented by Edward Stecke in the 1930s in Poland and used in the MG 42. The MG42 locking system actually locks completely and requires a short stroke barrel that travels backwards to unlock, compared to the StG45(M) system that never completely locks and does not require a moving barrel.

The CETME design inherits the StG45(M)'s fixed-barrel. However, the CETME Model 58 introduced a novel solution to the problem of cartridges sticking in the chamber. That is a fluted chamber, which are horizontal grooves in the chamber, that allow the cartridge cases to float on a layer of gas to aid extraction. The horizontal marking left on spent cartridge cases has become a signature of this design.

The first prototype rifles fired the same 7.92×33mm Kurz round as the StG45, and a variety of experimental 7.92 and 7.62mm cartridges were tested before settling on the 7.62×51mm CETME. This round was dimensionally identical to 7.62×51mm NATO, but with a lighter bullet and powder charge to reduce recoil, making fully automatic fire more controllable. Due to feedback from Heckler & Koch, the production rifle was chambered for the more powerful 7.62mm NATO. The Model B went on to be the foundation of the widely deployed Heckler & Koch G3 battle rifle.