Ludwig Vorgrimler (September 7, 1912 – February 23, 1983) is the man most commonly associated with the design of the Spanish roller-delayed CETME rifle, and its prolific offspring from the German gunmaker Heckler & Koch such as the G3, HK21, P9 and MP5.
He was assigned to Department 37, which was responsible for military small arms up to 15 mm in caliber and eventually led the sub-department in charge of aircraft weapon construction.
Though appearing simple its development during World War II was a hard technical and personal effort, as German engineering, mathematical and other scientists had to work together on a like-it-or-not basis led by von Lossnitzer.
Experiments showed roller-delayed blowback firearms exhibited bolt-bounce as the bolt opened at an extreme velocity of approximately 20 m/s (66 ft/s) during automatic fire.
The extremely high bolt carrier velocities problem was not solved by trial and error but mathematician Karl Maier finally provided a numerical analysis of the components and assemblies in the development project.
[1] By January 1944, Vorgrimler was ordered to design a heavy machinegun using the roller-delayed blowback operating system then under development for military rifles.
The French initially attempted to prevent him from leaving the country, but Vorgrimler and family were allowed to move to Madrid in September 1950.
[3] Beside the interest at home in Spain, the Modelo 2 attracted a lot of attention from the West German Border Guards (Bundesgrenzschutz), which sought a new service rifle.
Further development of the rifle produced the CETME Modelo B, which had been "improved" with the help of Heckler & Koch, receiving several modifications including the ability to fire from a closed bolt in both semi-automatic and automatic firing modes, a new perforated sheet-metal handguard (the folding bipod had been the foregrip in previous models), improved ergonomics, and a slightly longer barrel with a rifle grenade launcher mount.
However, the newly formed West German Army (Bundeswehr) now displayed interest and soon purchased a number of CETME rifles for further testing.