locking piece relative to the longitudinal axis reducing the bolt-bounce problem. With these angles the geometrical transmission ratio of the bolt carrier to the bolthead became 3:1, so the rear bolt carrier was forced to move 3 times faster than the bolthead. The rearward forces on the bolt carrier and receiver were 2:1. The force and impulse transmitted to the receiver increases with the force and impulse transmitted to the bolt carrier. Making the bolt carrier heavier lessens the recoil velocity. For Mausers StG 45(M) project Maier assumed a bolt head and bolt carrier (1 to 3 ratio). The prototype StG 45 (M) assault rifle had 18 longitudinal gas relief flutes cut in the chamber wall to assist the bloated cartridge casing from the chamber walls during extraction. Fluting the end of the chamber provides pressure equalization between the front outer surface of the cartridge case and its interior and thus ensures extraction without tearing the case making extraction easier and more reliable. In 1944 other German companies like Großfuß (de), Rheinmetall and C.G. Haenel showed interest in developing roller-delayed blowback small arms. Großfuß worked on a roller-delayed blowback MG 45 general-purpose machine gun that, like the StG 45 (M), had not progressed beyond the prototype stage by the end of World War II. After World War II, former Mauser engineers Ludwig Vorgrimler and Theodor Löffler perfected the mechanism between 1946 and 1950 while working for the French small arms manufacturer Centre d'Etudes et d'Armament de Mulhouse (CEAM). In 1950 Ludwig Vorgrimler was recruited to work for CETME in Spain. The first full-scale production rifle to utilize roller-delay was the Spanish CETME battle rifle, which was closely followed by the Swiss SIG SG 510 and the CETME Model B-based Heckler & Koch G3. The G3 bolt features an anti-bounce mechanism that prevents the bolt from bouncing off the barrel's breech surface. The G3's "bolt head locking lever" is a spring-loaded claw mounted on the bolt carrier that grabs the bolt head as the bolt carrier group goes into battery. The lever essentially ratchets into place with friction, providing enough resistance to being re-opened that the bolt carrier does not rebound. Due to the relative low bolt thrust exhibited by pistol cartridges the anti-bounce mechanism is omitted by Heckler & Koch on their roller-delayed blowback firearms chambered for pistols cartridges. Heckler & Koch's MP5 submachine gun is the most common weapon