WO2023001701A1

WO2023001701A1 - A self-loading firearm comprising a bolt lock

Info

Publication number: WO2023001701A1
Application number: PCT/EP2022/069808
Authority: WO
Inventors: Michael Cherry
Original assignee: Steel Core Defence Systems Limited
Priority date: 2021-07-21
Filing date: 2022-07-14
Publication date: 2023-01-26
Also published as: GB202110477D0

Abstract

A Self-Loading Firearm A self-loading firearm including a breech; and a bolt arranged to close one end of the breech; wherein the firearm includes a bolt channel within which the bolt is slidably located; the bolt channel includes a lateral pocket which defines a stop surface at a rear portion thereof; a bolt locking element is pivotally coupled at a forward end thereof to a rear portion of the bolt, the bolt locking element defining an engagement surface at a rear end thereof; wherein, when the bolt locking element is aligned with the lateral pocket, the bolt locking element has a first configuration in which it is aligned with the bolt channel and the bolt is slidable within the channel, and a second configuration in which at least a portion of the bolt locking element is located within the lateral pocket, the engagement surface of the bolt locking element is engaged with the stop surface, and the bolt is prevented from rearward displacement relative to the bolt channel.

Description

A Self-Loading Firearm

The present invention relates to a self-loading firearm, and in particular to a self-loading firearm that includes a hinged bolt locking element.

Self-loading firearms are well known. Typically, such firearms include a breech and a lockable bolt which selectively closes the breech. The lockable bolt is typically locked via a lock arrangement, wherein the bolt is rotatable and has a locked rotational orientation and an unlocked rotational orientation. Accordingly, the bolt has to both rotate and move axially within a bolt channel.

The present invention seeks to provide an alternative bolt arrangement in which the bolt simply reciprocates within a bolt channel. In other words, it only moves axially within the bolt channel.

According to a first aspect of the invention, there is provided a self-loading firearm including a breech; and a bolt arranged to close one end of the breech; wherein the firearm includes a bolt channel within which the bolt is slidably located; the bolt channel includes a lateral pocket which defines a stop surface at a rear portion thereof; a bolt locking element is pivotally coupled at a forward end thereof to a rear portion of the bolt, the bolt locking element defining an engagement surface at a rear end thereof; wherein, when the bolt locking element is aligned with the lateral pocket, the bolt locking element has a first configuration in which it is disposed within the bolt channel (e.g. the bolt and the bolt locking element together define a linear arrangement within the bolt channel) and both the bolt and the bolt locking element are slidable within the bolt channel, and a second configuration in which at least a portion of the bolt locking element is located within the lateral pocket, the engagement surface of the bolt locking element is engaged with the stop surface, and the bolt is prevented from rearward displacement relative to the bolt channel.

In the context of the present invention, the term "rearward" means a direction towards the butt or stock of the firearm, and the term "forward" means a direction towards the end of the barrel of the firearm (i.e., in the direction in which a projectile fired from the firearm moves).

It will be appreciated that the bolt is slidable within the bolt channel and can reciprocate therein, but is prevented from lateral displacement relative to the bolt channel. In the context of the present invention, the term "lateral" means a direction away from the longitudinal axis of the bolt channel (i.e. angled with respect to the longitudinal axis of the bolt channel). For example, lateral may include extending away from the longitudinal axis at an angle of from 20° to 160° (e.g. at an angle of up to 70° from a plane perpendicular to the longitudinal axis of the bolt channel). In certain embodiments, the stop surface may extend away from the longitudinal axis of the bolt channel at an angle of from 60° to 120°.

The skilled person will appreciate that the arrangement of the bolt locking element and the bolt permits the rear end of bolt locking element to move laterally relative to the bolt. Thus, while the bolt is prevented from lateral displacement, the rear end of the bolt locking element may be displaced laterally into the pocket when the bolt locking element is aligned with the pocket. In such an arrangement, the bolt locking element is angled with respect to the bolt/bolt channel.

As engagement between the engagement surface of the bolt locking element and the stop surface of pocket prevents rearward displacement of bolt locking element when the rear end portion of the bolt locking element is located within the lateral pocket, and the bolt is coupled to the bolt locking element, the bolt is prevented from rearward displacement within the bolt channel and is thus locked in position when at least a portion of the bolt locking element is disposed within the pocket.

In an embodiment of the invention, the firearm further includes a bolt driver which is operatively coupled to the rear end of the bolt locking element, wherein the bolt driver urges the bolt locking element to move from its second configuration to its first configuration. The bolt driver (sometimes referred to as a bolt carrier) is an arrangement of one or more components which urges the bolt locking element out of the lateral pocket and into the bolt channel. The bolt and the bolt locking element are configured in a linear arrangement when they are both disposed in the bolt channel and in such a linear arrangement, they are able to reciprocate within the bolt channel. In this way, the bolt driver is able to unlock the bolt by urging the bolt locking element out of the lateral pocket and into the bolt channel.

Suitably, the bolt driver is slidably located within the bolt channel. In such an arrangement a rearward displacement of the bolt driver within the bolt channel may urge the bolt locking element to move from its second configuration to its first configuration. For example, the rearward displacement of the bolt driver may urge the rear end of the bolt locking element out of the pocket, thereby disengaging the engagement surface of the bolt locking element from the stop surface defined by the pocket. Thus, the bolt driver may exert a lateral force on the rear end of the bolt locking element in an opposite direction to the direction in which the pocket extends from the bolt channel.

In a further embodiment of the invention, the bolt driver further urges the bolt locking element to move from its first configuration to its second configuration. Thus, the bolt driver is able to lock the bolt and close the breech. In order to lock the bolt, the bolt locking element may include a locating lug carried by a rear portion of the bolt locking element; and the firearm may define a driver or guide channel within which the locating lug may be slidably coupled. Thus, the engagement of the locating lug within the driver channel may guide the movement of the rear portion of the bolt locking element. For example, the driver channel may include a first portion which is parallel to the bolt channel and a second portion which curves away from the bolt channel into the lateral pocket. In such an arrangement, as bolt driver urges the bolt forwards, the rear portion of bolt locking element is guided into lateral pocket by the engagement of the locating lug within the driver channel. The driver channel may be defined by a wall (e.g., a side wall portion) which defines a part of the bolt channel.

According to this arrangement, the bolt locking element is guided into and out from the lateral pocket by the driver or guide channel, as result of the forward and rearward displacement of the bolt driver within the bolt channel.

Suitably, the bolt driver is operatively connected to a gas-operated piston. In this way, the rearward displacement of the bolt driver is driven by a corresponding displacement of the piston.

In an embodiment of the invention, the gas-operated piston is disposed within a piston cylinder and a first end of the piston cylinder is in fluid communication with a gas port defined by a barrel of the firearm, wherein the piston is driven rearwards when pressurised gas from the barrel enters the first end of the piston cylinder. Such an arrangement which uses the high pressure gases from a cartridge to operate the bolt mechanism is well known. In such arrangements, a return spring is employed to drive the bolt mechanism forwards once the piston has reached the end of its travel. Thus, the invention may further include a return spring which biases the bolt driver to the front of the bolt channel. It will be appreciated that it is desirable for the bolt to remain locked when a cartridge is fired and can only be unlocked after the round has left the barrel. Accordingly, it is desired that a rearward force exerted by the cartridge upon firing is not capable of urging the bolt locking element out of the pocket, but that a rearward force exerted upon the bolt locking element by the bolt driver is the only action that is capable of urging the bolt locking element out of the pocket.

Accordingly, the bolt driver may comprise a main body and a linkage, wherein the linkage includes at a front end thereof a first pivot element via which the linkage is pivotally coupled to the rear end of the bolt locking element; and the linkage includes at a rear end thereof a second pivot element via which the linkage is pivotally coupled to a front portion of the bolt driver main body, wherein rearward displacement of the bolt driver main body urges the bolt locking element out of the lateral pocket. In other words, rearward displacement of the bolt driver moves the bolt locking element from its second configuration to its first configuration. It will be appreciated that in this embodiment, the linkage urges the bolt locking element into alignment with the bolt channel. This results from the rearward motion of the main body causing the linkage to pivot about second pivot, which in turn urges rear end of bolt locking element towards the bolt channel.

The linkage is able to exert a lateral force on the rear end of the bolt locking element which is in the opposite direction to the direction that the pocket extends from the bolt channel. This is in contrast with the force exerted on the bolt locking element by the bolt when a cartridge is fired. In this case, the bolt exerts a force on the front of the bolt locking element. As a result of the angled nature of the bolt locking element relative to the bolt, this force urges the bolt locking element into the pocket and the engagement of the engagement surface of the bolt locking element and the stop surface of the pocket prevents rearward displacement of the bolt as a result of the rearward force exerted on the bolt by the cartridge.

In a further embodiment of the invention, the bolt driver main body, linkage, bolt locking element and bolt together define a bolt assembly which has a first configuration in which the bolt assembly defines a linear arrangement within the bolt channel; and a second configuration in which the bolt drive main body and the bolt are disposed linearly within the bolt channel, and the linkage is arranged transverse to the bolt channel, wherein the front end of the linkage and the rear end of the bolt locking element are disposed in the lateral pocket. Suitably, the linkage defines a hinge between the bolt locking element and the bolt driver main body; and the hinge has an over-centre arrangement when the bolt assembly is in its second configuration, whereby the bolt locking element is prevented from lateral displacement out of the pocket. In other words, the second pivot is located further forwards than the first pivot and the linkage physically prevents displacement of the bolt locking element out of the pocket. Thus, the bolt locking element is thereby retained in its second configuration.

In a further embodiment of the invention, the piston cylinder includes a gas exhaust which is closable by the piston. For example, the gas exhaust may be disposed at a front portion of the cylinder and the exhaust is open when the piston has been displaced rearwards by the pressurised gas within the cylinder. Suitably, the gas exhaust may be disposed in the forward facing or front wall of the cylinder, such that the gas within the cylinder are vented in a forwards (i.e., towards the barrel of the firearm) direction. The gas exhaust may be opened when the piston is displaced rearwards by a pre-determined distance.

In an embodiment of the invention, the piston cylinder is arranged parallel to the barrel and defines a front end and a rear end; the piston cylinder includes a gas exhaust defined by a gas vent tube which is open at both ends and which is arranged co-axially with the cylinder; a first end of the gas vent tube is disposed within the cylinder and a second end of the gas vent tube defines a gas outlet port at the front end of the cylinder; the piston includes an annular gas contact surface which define a central bore that receives therein a portion of the gas vent tube when the piston is located towards the front of the cylinder. In this arrangement, the piston effectively closes the first end of the gas vent tube when the gas vent tube is disposed within the piston. However, the piston is axially displaceable within the cylinder, whereas the gas vent tube is fixed relative to the cylinder. Therefore, as the piston is driven rearwards as a result of the pressurised gases from the barrel impinging on the gas contact surface, the first end of gas vent tube will no longer be located within the piston and the first end of the gas vent tube becomes open to the compressed gases within the cylinder. In this arrangement, the compressed gases within the cylinder can pass into the first end of the gas vent tube, pass through the gas vent tube and exit the cylinder via the gas outlet port. It will be appreciated that in this arrangement, the gases within the cylinder are vented forwards after they have driven the piston rearwards.

By venting the spent gases from the cylinder forwards, there are no lateral forces exerted on a main body portion of the firearm as a result of venting the pressurised gases from the cylinder. While it is possible to locate the pocket at any angle relative to a vertical plane, the pocket is suitably located vertically above the bolt channel or vertically below the bolt channel.

As noted above, in the context of the present invention, the term forwards means towards the muzzle end of the barrel and the term rearwards means the opposite direction, i.e. towards the stock end of the firearm. Similarly, the terms above and below, and up and down refer to the normal orientation of the firearm in use. Thus, where a magazine depends downwardly from the firearm, the downward direction is defined as the direction in which the magazine extends from the firearm.

The skilled person will appreciate that the features described and defined in connection with the aspects of the invention and the embodiments thereof may be combined in any combination, regardless of whether the specific combination is expressly mentioned herein. Thus, all such combinations are considered to be made available to the skilled person.

An embodiment of the invention will now be described, by way of example only, with reference to the accompanying drawing in which:

Figures la to le show the firing sequence of a self-loading firearm according to a first embodiment of the invention; and

Figures 2a to 2d show the movement of the bolt, bolt locking element and bolt driver of the firearm shown in Figures la to le.

For the avoidance of doubt, the skilled person will appreciate that in this specification, the terms "up", "down", "front", "rear", "upper", "lower", "width", etc. refer to the orientation of the components as found in the example when installed for normal use as shown in the Figures.

Furthermore, the term "forward" or "forwards" refers to a direction towards the muzzle end of the barrel of the embodiment shown and the term "rear" or "rearwards" refers to a direction opposite to the barrel, i.e. towards the stock of the embodiment.

Figures la to le show a self-loading firearm 2 comprising a breech 4 which opens at its forward end into a barrel 6 and which is selectively closed at its rear end by a bolt 8. The bolt 8 is lockable in its closed configuration (shown in Figure la) by a bolt locking element 10. As shown in Figure la, the bolt is slidably retained within a bolt channel 4a which extends rearwards from the breech 4. The bolt channel 4a defines a lateral pocket 4b behind the bolt 8 when the bolt 8 is in its closed position. The lateral pocket 4b is wedge-shaped with a rear wall 4c that defines an angle of 15° from a vertical axis perpendicular to the bolt channel 4a. The bolt locking element 10 is coupled to a bolt driver 12 by a hinged linkage 14.

The bolt driver 12 is also connected to a rear end of a piston 16 which is disposed within a cylinder 19a defined by an upper body 19 of the firearm 2. At a front end of the piston 16 is a cavity 18 which is partially closed at its front end by an annular contact surface 20. A shown in Figure la, a gas vent tube 22 is located within the central aperture defined by the annular contact surface 20. The gas vent tube 22 is fixed relative to the cylinder 19a and the upper body 19, so that the piston 16 moves axially relative to the gas vent tube 22. The annular contact surface 20 of the piston forms a substantially gas-tight seal with the gas vent tube 22. The gas vent tube 22 is open at its rear end (the end located within the piston cavity 18 as shown in Figure la) and a front end of the gas vent tube 22 terminates in a gas exhaust port 24.

Figures la to le show the operational sequence of the firearm 2.

As noted in Figure la, the bolt 8 is locked in its closed configuration by the bolt locking element 10. A trigger 26 has been operated and a round 28 has been forced out of a cartridge 30 by expanding pressurised gases 32. A portion of the pressurised gases are directed into a front end of the cylinder 19a via a gas inlet conduit 34, where they impinge upon the annular contact surface 20 of the piston 16. This forces the piston 16 rearwards.

Figure lb shows that the bolt driver 12 is urged rearwards as the piston 16 is urged rearwards.

This in turn urges a rear portion of the hinged linkage 14 rearwards. The rearward displacement of the rear portion of the hinged linkage 14 urges a front portion of the hinged linkage 14 to move downwards, which in turn urges a rear portion of the bolt locking element 10 downwards.

As shown in Figure lb, the rear end of the gas vent tube 22 is still located within the piston cavity 18, so the force exerted by the pressurised gas is still impinging on the annular contact surface 20 of the piston 16, which continues to urge the piston 16 rearwards. Furthermore, as the bolt locking element 10 is still partially located within the pocket 4b, the bolt 8 is still locked in its closed configuration.

Figure lc shows the piston 16 in a more rearward position within the cylinder 19a. In this position, the rear end of the gas vent tube 22 is not longer located within the piston cavity 18. Accordingly, the pressurised gases 32 within the cylinder 19a are able to enter the rear end of the gas vent tube 22 and vent to the atmosphere via the gas vent tube 22 and the gas exhaust port 24. As shown in Figure lc, the pressurised gases from the cylinder 19a are vented forwards once the piston 16 has travelled rearwards by the distance that the gas vent tube 22 extends into the piston cavity 18.

In addition to the rear end of the gas vent tube 22 no longer being located within the piston cavity 18, the bolt locking element 10 is no longer within the pocket 4b. This effectively unlocks the bolt 8 and permits it to travel rearwards within the bolt channel 4a.

The mass of the bolt driver 12 causes it to continue to move rearwards as a result of the kinetic energy imparted to it by the piston 16.

Figures Id and le show the continued rearward movement of the bolt driver 12, the linkage 14, the bolt locking element 10 and the bolt 8. From this point, the actions are similar to those of a known self-loading firearm, namely, the bolt 8 continues rearwards until the spent cartridge 30 reaches an ejection port (not shown), where it is ejected from the firearm 2. A return spring (also not shown) then urges the bolt driver 12 forwards, whereupon the linkage 14, the bolt locking element 10 and the bolt 8 are also urged forwards. The bolt 8 engages a fresh cartridge 30 from a magazine 36 and the fresh cartridge 30 is urged into the breech 4 by the forward movement of the bolt 8.

It will be appreciated that the trigger assembly is a conventional trigger assembly that includes a safe configuration, a single shot configuration and a fully automatic configuration. As the trigger assembly is a conventional assembly, it needs not be described in detail herein. Figures 2a to 2d show the bolt 8, the bolt locking element 10, the hinged linkage 14, the bolt driver 12, the bolt channel 4a and the pocket 4b in more detail, again showing a sequence of movements.

Figure 2a shows the bolt 8 in its locked configuration, with the bolt locking element 10 located within the pocket 4b. In this configuration, a bolt locking element engagement surface 10a engages a stop surface defined by the rear wall 4c of the pocket 4b. Additionally, it will be noted that the hinged linkage 14 includes a front pivot 14a and a rear pivot 14b. The front pivot 14a pivotally couples a front portion of the hinged linkage 14 to the rear of the bolt locking element 10. Similarly, the rear pivot 14b pivotally couples a rear portion of the hinged linkage 14 to a forward extending arm 12a of the bolt driver 12. In this arrangement, the hinged linkage 14 can pivot relative to the bolt driver 12 and the bolt locking element 10.

As shown in Figure 2a, the hinged linkage 14 is in an "over centre" configuration, wherein the rear pivot 14b is further forward than the front pivot 4a. This configuration prevents a downward force exerted on the rear of the bolt locking element 10 as a result of a rearward force exerted by the bolt 8 and the inclined rear wall 4c from displacing the rear of the bolt locking element 10 downwards. This configuration of the hinged linkage counteracts any such downward force exerted upon the rear portion of the bolt locking element 10.

Figure 2b shows the bolt driver 12 after it has moved rearwards by a small distance by the action of the piston. It can be seen that the hinged linkage 14 is no longer in an over-centre configuration and the rear pivot 14 b is now located rearwards of the front pivot 14a. Flowever, the bolt is still locked, as the bolt locking element 10 is still located within the pocket 4b and the bolt locking element engagement surface 10a is still engaged with the stop surface defined by the rear wall 4c of the pocket 4b.

Figure 2c shows the bolt 8 still in a locked configuration. Flowever, the bolt driver 12 has moved the rear of the hinged linkage rearwards, which in turn has urged the rear of the bolt locking element 10 downwards and only a small portion of the engagement surface 10a is still engaged with the pocket stop surface. It will be noted that the hinged linkage converts rearward displacement of the bolt driver 12 to downward displacement of the rear of the bolt locking element 10. Figure 2d shows the bolt 8 in an unlocked configuration in which it is free to move rearwards within the bolt channel 4a. In this configuration, the bolt locking element 10 is no longer located within the pocket 4b and is able to move axially within the bolt channel 4b with the bolt driver 12 and the hinged linkage 14.

Figures 2c and 2d also show a driver channel 40 which is defined by a side wall portion of the bolt channel 4a. The driver channel 40 includes a linear portion 40a which is parallel to the bolt channel 4a and a curved portion 40b which extends upwards into the pocket 4b. The front pivot 14a extends laterally from the bolt locking element 10 and defines a locating lug (not shown) that is located within the driver channel 40.

It will be appreciated that Figures 2a to 2d show the bolt 8 as it moves from its locked configuration to its unlocked configuration. Flowever, the reverse occurs when the bolt driver 12 is urged forwards under the action of the return spring (not shown). In this situation, as the rear of the bolt locking element 10 approaches the pocket 4b, the curved portion 40b of the driver channel directs the locating lug and consequently the rear of the bolt locking element 10 upwards towards the pocket 4b. The bolt locking element 10 and the hinged linkage 14 then adopt sequentially the configurations shown in Figures 2c, 2b and 2a. When the bolt 8, the bolt locking element 10, the hinged linkage 14 and the bolt driver 12 are in the configuration shown in Figure 2a, the bolt 8 is locked and the firearm 2 is ready to fire again.

It will be appreciated that the firearm 2 further includes a manual charging lever (not shown) that is useable to cycle the bolt from its locked configuration, through its unlocked configuration and back to its locked configuration. The charging lever is arranged to engage the bolt driver 12 on a rearward stroke to fully open the bolt 8. When the charging lever is released, the return spring urges the bolt 8 forwards, whereupon it collects a fresh cartridge 30 from the magazine 36 and returns to its locked configuration with the cartridge 30 located within the breech 4 and the trigger assembly re-set to a fire configuration. As such manual charging levers are well known, it will not be described in detail herein.

Claims

1. A self-loading firearm including a breech; and a bolt arranged to close one end of the breech; wherein the firearm includes a bolt channel within which the bolt is slidably located; the bolt channel includes a lateral pocket which defines a stop surface at a rear portion thereof; a bolt locking element is pivotally coupled at a forward end thereof to a rear portion of the bolt, the bolt locking element defining an engagement surface at a rear end thereof; wherein, when the bolt locking element is aligned with the lateral pocket, the bolt locking element has a first configuration in which it is disposed within the bolt channel and the bolt and the bolt locking element are both slidable within the channel, and a second configuration in which at least a portion of the bolt locking element is located within the lateral pocket, the engagement surface of the bolt locking element is engaged with the stop surface, and the bolt is prevented from rearward displacement relative to the bolt channel.

2. A self-loading firearm according to Claim 1, wherein the firearm further includes a bolt driver which is operatively coupled to the rear end of the bolt locking element, wherein the bolt driver urges the bolt locking element to move from its second configuration to its first configuration.

3. A self-loading firearm according to Claim 2, wherein the bolt driver is slidably located within the bolt channel.

4. A self-loading firearm according to Claim 2 or Claim 3, wherein the bolt driver further urges the bolt locking element to move from its first configuration to its second configuration; the bolt locking element includes a locating lug carried by a rear portion of the bolt locking element; the firearm defines a driver channel; and the locating lug is slidably coupled within the driver channel.

5. A self-loading firearm according to Claim 4, wherein the driver channel includes a first portion which is parallel to the bolt channel and a second portion which curves away from the bolt channel into the lateral pocket.

6. A self-loading firearm according to any of Claims 2 to 5, wherein the bolt driver is operatively connected to a gas-operated piston.

7. A self-loading firearm according to Claim 6, wherein the gas-operated piston is disposed within a piston cylinder and a first end of the piston cylinder is in fluid communication with a gas port defined by a barrel of the firearm, wherein the piston is driven rearwards when pressurised gas from the barrel enters the first end of the piston cylinder.

8. A self-loading firearm according to Claim 7, wherein the bolt driver further includes a return spring which biases the bolt driver to the front of the bolt channel.

9. A self-loading firearm according to Claim 7 or Claim 8, wherein the piston cylinder includes a gas exhaust which is closable by the piston.

10. A self-loading firearm according to Claim 9, wherein the gas exhaust is defined in a forward-facing wall of the cylinder.

11. A self-loading firearm according to Claim 9 or Claim 10, wherein the piston cylinder is arranged parallel to the barrel and defines a front end and a rear end; the piston cylinder includes a gas vent tube which defines the gas exhaust, which is open at both ends and which is arranged co-axially with the cylinder; a first end of the gas vent tube is disposed within the cylinder and a second end of the gas vent tube defines a gas outlet port at the front end of the cylinder.

12. A self-loading firearm according to Claim 11, wherein the piston defines an axial aperture at a front portion thereof that receives therein a portion of the gas vent tube when the piston is located towards the front of the cylinder.

13. A self-loading firearm according to Claim 12, wherein a substantially gas-tight seal is provided between the axial aperture and the gas vent tube when the gas vent tube is disposed within the axial aperture.

14. A self-loading firearm according to any of Claims 2 to 13, wherein the bolt driver comprises a main body and a linkage, wherein the linkage includes at a front end thereof a first pivot element via which the linkage is pivotally coupled to the rear end of the bolt locking element; and the linkage includes a rear end thereof a second pivot element via which the linkage is pivotally coupled to a front portion of the bolt driver main body, wherein rearward displacement of the bolt driver main body urges the bolt locking element out of the lateral pocket.

15. A self-loading firearm according to Claim 14, wherein the bolt driver main body, linkage, bolt locking element and bolt define a bolt assembly which has a first configuration in which the bolt assembly defines a linear arrangement within the bolt channel; and a second configuration in which the bolt drive main body and the bolt are disposed within the bolt channel, and the linkage is arranged transverse to the bolt channel, wherein the front end of the linkage and the rear end of the bolt locking element are disposed in the lateral pocket.

16. A self-loading firearm according to Claim 15, wherein the linkage defines a hinge between the bolt locking element and the bolt driver main body; and the hinge has an over-centre arrangement when the bolt assembly is in its second configuration, whereby the bolt locking element is prevented from lateral displacement out of the pocket.

17. A self-loading firearm according to any of Claims 1 to 16, wherein the lateral pocket extends upwards from the bolt channel or depends downwards from the bolt channel.