In firearms operating systems, the term roller locked refers to locking the bolt with rollers. Notable examples of firearms using this method are the Polish wz.37 semi-automatic rifle designed by Edward Stecke,

MG 42 The MG 42 (shortened from German: ''Maschinengewehr 42'', or "machine gun 42") is a German recoil-operated air-cooled general-purpose machine gun used extensively by the Wehrmacht and the Waffen-SS during the second half of World War II. Enter ...

general-purpose machine gun A general-purpose machine gun (GPMG) is an air-cooled, usually belt-fed machine gun that can be adapted flexibly to various tactical roles for light and medium machine guns. A GPMG typically features a quick-change barrel design calibered fo ...

, which copied the solution of engineer Stecke and the CZ 52

semi-automatic pistol A semi-automatic pistol (also called a self-loading pistol, autopistol, or autoloading pistol) is a repeating firearm, repeating handgun that automatically ejects and loads cartridge (firearms), cartridges in its chamber (firearms), chamber afte ...

. It was also applied in the experimental ''Gerät 03''

semi-automatic rifle A semi-automatic rifle is a type of rifle that fires a single round each time the Trigger (firearms), trigger is pulled while automatically loading the next Cartridge (firearms), cartridge. These rifles were developed Pre-World War II, and w ...

and '' Gerät 06'' and EM-1 experimental

assault rifle An assault rifle is a select fire rifle that uses an intermediate cartridge, intermediate-rifle cartridge and a Magazine (firearms), detachable magazine.C. Taylor, ''The Fighting Rifle: A Complete Study of the Rifle in Combat'', F.A. Moyer '' ...

s. The MG 42's lineage continued past World War II, forming the basis for the nearly identical MG1 (MG 42/59), chambered in

7.62×51mm NATO The 7.62×51mm NATO (official NATO nomenclature 7.62 NATO) is a rimless, straight walled, bottlenecked, centerfire rifle cartridge. It is a standard for small arms among NATO countries. First developed in the 1950s, the cartridge had first be ...

, which subsequently evolved into the MG1A3, and later the

Bundeswehr The (, ''Federal Defence'') are the armed forces of the Germany, Federal Republic of Germany. The is divided into a military part (armed forces or ''Streitkräfte'') and a civil part, the military part consists of the four armed forces: Germ ...

's MG 3, Italian MG 42/59, and Austrian MG 74. It also spawned the Yugoslav unlicensed nearly identical Zastava M53.

History

The origin of the roller-locking is debated: even though the general principle of utilizing "ball bearing parts" under radial pressure "for preventing uncoupling of the coupling members" was known no later than 1910s, it was apparently not used in firearms until 1930s. The first rifle to use a solution similar to the modern one was the Polish experimental semi-automatic rifle wz.37 designed by engineer Edward Stecke. However, it did not use rollers, only longitudinal locking elements. Probably based on its design, the Germans developed the MG42, replacing the longitudinal locking elements with rollers.

Mechanism

In roller-locked arms in the locked position during firing, the rollers rest on parallel surfaces relative to the

bore axis The bore axis of a firearm is the longitudinal axis through the geometric center of the gun barrel. In a rifling, rifled barrel, the projectile (bullet/round shot, ball, pellet (air gun), pellet or shotgun slug, slug) will spin around the bore axis ...

on the bolt head, so no amount of force pushing back on the bolt can cause the bolt to unlock. When chambering a fresh cartridge the bolt head is used to push out the rollers. For that the bolt head ends in an angled/oblique wedge to smoothly move the rollers outwards into their lockup position. Roller locking is used by the CZ 52 pistol. The slide, barrel, locking piece, and rollers are shown here. Normally the recoil spring pushes the locking piece rearward, which in turn pushes the barrel back and holds the locking rollers. (In some of these pictures the spring is removed.) When the gun is fired, the barrel, slide, and locking piece (right side of picture) will move backward a short distance, while the locking piece will be stopped by a tab on the frame, shown on the left with a stick pointing out the mating surface. With the locking piece stopped by the tab, the rollers will continue rearward with the slide, until they reach the recessed portion of the locking piece. The rollers will then be allowed to move inward and release from their indentations in the slide, releasing the slide from the barrel. At about the same time, the barrel will be stopped by the locking piece. Momentum will carry the slide back against the pressure of the recoil spring where extraction and feeding of a fresh cartridge happen similarly to other designs. As the slide moves forward, the locking piece maintains outward pressure on the rollers. When the recesses in the slide are positioned with the rollers, the locking piece will push them out into the recesses and move forward, locking the barrel to the slide again, the barrel and slide will move forward a small amount and stop. Unlike a standard Browning short-recoil action, there is no tipping of the barrel during operation.

Platforms

Other locking systems with similarities

* Roller-delayed blowback as in the HK G3, where similar rollers are used is sometimes mistakenly called roller locked, but there is no genuine locking of the bolt and no recoiling of the barrel in delayed blowback action as the rollers rest on angled/oblique surfaces, so applying a backward force on the bolt will cause it to unlock. * The flapper locking method and roller locking are similar in concept. * The ball-bearing roller locking system used in straight-pull rifles like the

Anschütz 1827 Fortner Anschütz 1827 Fortner is a straight pull rifles, straight-pull action biathlon rifle designed by Peter Fortner junior and produced in cooperation with J. G. Anschütz. The rifle has been dominant in the sport of biathlon since the late 1980s, ...

, Crossfire MK1, Heym SR 30 and Savage Impulse. * Bearing-delayed blowback as in the Mean arms upper receiver for an AR-15–style rifle. * The collet locking system used in the Blaser R8/ R93/ Blaser Tactical and Thompson .30-06 prototype which uses an expanding

collet A collet is a segmented sleeve, band or ''collar''. One of the two radial surfaces of a collet is usually tapered (i.e a truncated cone) and the other is cylindrical. The term ''collet'' commonly refers to a type of chuck that uses collets ...

in a similar fashion.

References

External links