In firearms operating systems, the term roller locked refers to locking the bolt with
rollers. Notable examples of firearms using this method are the
MG 42 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 for v ...
, and the
CZ 52 semi-automatic pistol. It was also applied in the experimental
''Gerät 03'' semi-automatic rifle and ''Gerät 06'' and
EM-1 experimental assault rifles.
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, which subsequently evolved into the MG1A3, and later the
Bundeswehr
The ''Bundeswehr'' (, meaning literally: ''Federal Defence'') is the armed forces of the Federal Republic of Germany. The ''Bundeswehr'' is divided into a military part (armed forces or ''Streitkräfte'') and a civil part, the military part con ...
's
MG 3
The MG3 is a small car produced by the Chinese automotive company SAIC. The first generation, marketed as the MG3 SW, is based on the British made Rover Streetwise, which itself was based on the Rover 25, while the second generation, introdu ...
, Italian MG 42/59 and Austrian MG 74. It also spawned the Yugoslav unlicensed nearly identical Zastava M53.
History
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.
Mechanism
![Delayed blow back breech with locking rollers (en)](https://upload.wikimedia.org/wikipedia/commons/5/52/Delayed_blow_back_breech_with_locking_rollers_%28en%29.svg)
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 rifled barrel, the projectile (bullet/ball, pellet or slug) will spin around the bore axis as it goes through the barrel.
Boresighting is a ...
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. 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 backwards 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 will 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 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.
Other locking systems with similarities
*
Roller-delayed blowback as in the
HK G3
The Heckler & Koch G3 (''Gewehr'' 3) is a 7.62×51mm NATO, select-fire battle rifle developed in the 1950s by the German armament manufacturer Heckler & Koch (H&K) in collaboration with the Spanish state-owned design and development agency ...
, 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 backwards force on the bolt will cause it to unlock.
* The
flapper locking
Flapper locking is a type of locking mechanism used in self-loading firearms. It involves a pair of flappers on the sides of the bolt that each lock into an outwards recess in the receiver as the bolt is in battery. As the bolt is forced backwards ...
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
The Heym SR 30 is a straight-pull rifle produced in Germany by Heym. The rifle is also available in a left hand version.
Locking mechanism
The mechanism uses 6 ball bearings symmetrically positioned around the circumference of the bolt ...
and
Savage Impulse,
* The collet locking system used in the
Blaser R8/
R93/
Blaser Tactical and
Thompson .30-06 prototype which uses an expanding
collet in a similar fashion.
See also
*
Rotating bolt
Rotating bolt is a method of locking the breech (or rear barrel) of a firearm closed for firing. Johann Nicolaus von Dreyse developed the first rotating bolt firearm, the " Dreyse needle gun", in 1836. The Dreyse locked using the bolt handle ...
*
Interrupted screw
Breech from Russian 122 mm M1910 howitzer, modified and combined with 105 mm H37 howitzer barrel
An interrupted screw or interrupted thread is a mechanical device typically used in the breech of artillery guns. It is believed to have be ...
References
External links
How Does It Work: Roller LockingForgotten Weapons
{{DEFAULTSORT:Roller Locked
Firearm actions