WO2007118278A1

WO2007118278A1 - A bolt head locking arrangement for firearm weapons

Info

Publication number: WO2007118278A1
Application number: PCT/AU2007/000493
Authority: WO
Inventors: Douglas Rawson-Harris
Original assignee: Goodcart Pty Ltd
Priority date: 2006-04-19
Filing date: 2007-04-17
Publication date: 2007-10-25
Also published as: EP2010854A1; US20090101000A1; AU2007240122A1

Abstract

A bolt head locking arrangement for a recoil operated weapon where projectile is expelled by discharging a cartridge. The weapon comprising an action body, a barrel, and a bolt assembly, the bolt assembly being slidable within the action body. The bolt assembly comprising a bolt head, a locking slide and a firing pin, and a locking means arranged so that, upon loading a new cartridge for discharging, the locking means positively lock the bolt head such that, for a predetermined amount of time after the loaded cartridge is discharged, the locked bolt head stops the cartridge from retreating into the action body. The locking means is substantially in an in-line configuration with the bolt assembly. The locking means are arranged so that the recoil momentum of the weapon, caused by the discharge, is used for unlocking the bolt head, wherein the locking means are arranged so that, upon discharge of the cartridge, the locking slide recoils backwards and, once the bolt head is unlocked, the inertia of the locking slide facilitates the recoil of the bolt head.

Description

A BOLT HEAD LOCKING ARRANGEMENT FOR FIREARM WEAPONS

TECHNICAL FIELD

The present invention relates to a locking arrangement for a weapon. In particular, the invention relates to a locking/unlocking arrangement for the bolt head of a firearm.

BACKGROUND OF THE INVENTION

The problem associated with foreign matter penetrating the internal mechanisms of a firearm during the discharge of a cartridge is well known in the weapon industry. The foreign matter in question includes various gases and particulates released during the discharge, as well as other contaminants, such as water vapour.

To alleviate or ameliorate this problem, various systems have been designed to impose a time delay between the discharge of the cartridge and the release of the bolt head, thus minimising the amount of foreign matter penetrating the inside of the weapon during the cartridge discharge. Some of these systems rely solely on the mass of the bolt head and the spring constant of the associated recoil spring to resist the initial gas pressure of the cartridge discharge. Other systems have a dedicated gas tube, which the gas pressure has to traverse before reaching the bolt head, thus creating a time delay between the cartridge discharge and the recoil of the bolt head. Yet other arrangements use a toggle which the gas pressure has to break before it can propagate inside the weapon. All of these systems are somewhat complex and inefficient.

US Patent 4301712, by Cristina discloses a hammer lock which locks the hammer of the weapon, thus preventing opening of the weapon bridge until bridge pressure drops to a residual safe level. However, the locking mechanism disclosed in this patent is based on an abutment engagement which is configured so as to resists the gas pressure initially, but to be overcome at a later stage. Because of this, and since both the locking and the unlocking of this locking arrangement depend on a single abutment engagement, it is believed that this engagement offers only a partial lock that allows some gas pressure to penetrate even at the initial stages of the discharge.

GIAT FAMAS assault rifle, on the other hand, employs a delay lever interposed between the bolt itself and the bolt carrier. When a cartridge is discharged, the bolt begins to move back under the pressure. However, at the initial stages, when the pressure is high, the delay lever transforms the short movement of the bolt into the longer movement of the bolt carrier, thus delaying the opening of the bolt. However, this system is also too complex and offers only partial locking.

Some other prior art such as US 3998126 by Rudd, US 4232583 by Harrison and WO 2005/031242 by Abdullaev et al also utilise delay mechanisms that slow down the bolt head after a cartridge is discharged to minimise the penetration of pressure caused by the discharge into the action body. This prior art utilise components such as delay rollers, cam mechanisms and the like that are of complicated design and manufacture and readily prone to wear.

US 4604942 by Benelli discloses a bolt head that is positively locked for a predetermined time after a loaded cartridge is discharged. However, the bolt head must be rotated (or twisted) to become unlocked. The bolt head has two projections which in conjunction with associated grooves of the barrel comprise a locking means. A disadvantage of this locking means is that fouling, such that caused by debris or dirt entering the breech may result.

Accordingly, it would be advantageous if a relatively simple and reliable system is designed which can lock positively the bolt head of a firearm for a particular duration of time after a cartridge discharge, so as to minimise the penetration of discharge generated substances into the firing mechanism of the weapon during and immediately after the discharge.

SUMMARY OF THE INVENTION

According to a first aspect, the bolt head locking arrangement for a recoil operated weapon where projectile is expelled by discharging a cartridge, the weapon comprising a longitudinal action body, a longitudinal barrel, the barrel being a part of or axially attached to the action body, and a bolt assembly, the bolt assembly being slidable within the action body so as to affect at least one of; loading cartridges in the barrel for discharging, discharging cartridges and extracting discharged cartridges; the bolt assembly comprising a bolt head, a locking slide and a firing pin, at least some of which being arranged for moving with respect to each other, wherein the arrangement further comprises locking means arranged so that, upon loading a new cartridge for discharging, the locking means positively lock the bolt head such that, for a predetermined amount of time after the loaded cartridge is discharged, the locked bolt head stops the cartridge from retreating into the action body, thus eliminating the penetration of pressure caused by the discharge into the action body, the locking means is substantially in an in-line configuration with the bolt assembly, and said locking means are arranged so that the recoil momentum of the weapon, caused by the discharge, is used for unlocking the bolt head, wherein the locking means are arranged so that, upon discharge of the cartridge, the locking slide recoils backwards and, once the bolt head is unlocked, the inertia of the locking slide facilitates the recoil of the bolt head.

Preferably, said locking means are arranged so that, after the bolt head is unlocked, a residual of the gas pressure formed during the discharge is used for assisting with the recoil of the bolt head.

Preferably, said locking means are arranged so that, upon loading a cartridge, a first abutment surface is brought into an abutment engagement with the locking means to bring them into an abutment engagement with a second abutment surface, thus locking the bolt head, the locking means being further arranged so that a predetermined time after the discharge of the cartridge, the first abutment surface is withdrawn from a locking engagement with the locking means, thus releasing them from the locking abutment engagement with the second abutment surface and allowing the bolt head to recoil.

Preferably, said locking slide comprises a timing surface of predetermined length and the locking means comprise at least one locking lug that is engageable with the timing surface so as to move between open and closed configuration, wherein in the closed configuration the at least one lug is located within the cross-sectional area of the bolt head to allow the sliding movement of the head within the action body, while in open configuration the at least one lug extends beyond this cross-sectional area to abut with an abutment surface of the action body and prevent rearward movement of the bolt head, wherein in use; when the bolt assembly is moved forward to load a cartridge, the locking slide moves with respect to the bolt head so that the timing surface engages the at least one lug to push it into an open configuration, so that when the bolt head is moved fully forwardly, the bolt head is locked in a sealing engagement with the sealing inner surface of the barrel and in an abutment engagement with the abutment surface of the action body; and upon discharging the cartridge, the locking slide moves backwards, causing the entire predetermined length of the timing surface to withdraw from its engagement with the at least one lug and allow the at least one lug to move into closed configuration, thus unlocking the bolt head and allowing it to recoil.

Preferably, at least one of the following parameters can be changed to adjust the time delay, during which the bolt head is locked, so as to allow the weapon to discharge a cartridge having different charge characteristics or projectile mass; the length of the timing surface; the mass of the locking slide, the bolt head, the bolt assembly or the mass of the entire weapon; the mechanical characteristics of a recoil spring used to move the bolt assembly forwards after a recoil.

Preferably, said following parameters can be changed to adjust the time delay, during which the bolt head is locked, so as to allow the weapon to discharge a cartridge having different charge characteristics or projectile mass, in the following manner; increasing the length of the timing surface to allow for larger charge to be used; decreasing the mass of the locking slide, the bolt head, the bolt assembly or the mass of the entire weapon to allow for larger charge to be used; to reduce the spring constant of the recoil spring to allow for larger charge to be used.

Preferably, said firing pin is arranged to be able to discharge a cartridge only if the bolt head is substantially in a locked configuration. Preferably, said firing pin is arranged to protrude through an opening in the bolt head so that, when the bolt head is not in a locked configuration, the firing pin is unable to reach the cartridge and effect a discharge.

According to a second aspect, the method for locking and unlocking a bolt head in a recoil operated weapon which expels projectiles by discharging a cartridge, where at least one of loading cartridges for discharging, discharging cartridges and extracting discharged cartridges is assisted by a bolt head assembly including a bolt head, the method comprising the step of locking, upon loading a new cartridge for discharging, the bolt head in a substantially in-line configuration such that, for a predetermined amount of time after the loaded cartridge is discharged, the locked bolt head prevents the cartridge from retreating into the action body, thus eliminating the penetration of pressure caused by the discharge into the action body, and the recoil momentum of the weapon, caused by the discharge, is used for unlocking the bolt head, and said method further comprising the step of allowing a member of the bolt head assembly, the member being engageable with the bolt head, to recoil, upon discharge of the cartridge, the inertia of the member being used to, upon unlocking of the bolt head, facilitate the recoil of the bolt head.

Preferably, after the bolt head is unlocked, a residual of the gas pressure, formed during the discharge, is used for assisting with the recoil of the bolt head.

Preferably, locking of the bolt head is arranged by providing a first abutment surface that, upon loading a cartridge, is brought into an abutment engagement with locking means to bring them into an abutment engagement with a second abutment surface, thus locking the bolt head, unlocking of the bolt head a predetermined delay time after the discharge of the cartridge being facilitated by withdrawing the first abutment surface from the .locking engagement with the locking means, thus releasing the locking means from the locking abutment engagement with the second abutment surface and allowing the bolt head to recoil.

Preferably, said method further includes the step of arranging so that, after a discharge, the first abutment member recoils immediately, so that its predetermined length defines the duration of engagement between the first abutment surface and the locking means, thus also defining the predetermined delay time of the recoil of the bolt head. Preferably, to allow the weapon to discharge a cartridge having different charge characteristics or projectile mass, the method comprises the step of adjusting the time delay, during which the bolt head is locked, by changing at least one of the following parameters; the length of the timing surface; the mass of the bolt head, the bolt assembly or the mass of the entire weapon; the mechanical characteristics of a recoil spring used to move the bolt assembly forwards after a recoil.

Preferably, to allow the weapon to discharge a cartridge having different charge characteristics or projectile mass, the method comprises the step of adjusting the time delay, during which the bolt head is locked, by changing at least one of the following parameters in the following manner; increasing the length of the timing surface to allow for larger charge to be used; decreasing the mass of the locking slide, the bolt head, the bolt assembly or the mass of the entire weapon to allow for larger charge to be used; to reduce the spring constant of the recoil spring to allow for larger charge to be used.

Preferably, said method further including the step of arranging a cartridge to be discharged only if the bolt head is substantially in a locked configuration.

Preferably, a firing pin is arranged to protrude through an opening in the bolt head so that, when the bolt head is not in a locked configuration, the firing pin is unable to reach the cartridge and effect a discharge.

According to a third aspect, there is provided a locking arrangement for a bolt head of a recoil operated firearm having a barrel; wherein, in locked configuration, the locking arrangement is adapted to retain the bolt head of the firearm in abutting engagement with the barrel for a predetermined time delay subsequent to discharge of the firearm; the locking arrangement comprising at least one lug pivotally attached to the bolt head; the at least one lug being operable between a first retracted unlocked position and a second extended locking position; the locking arrangement further comprising a locking slide provided with a timing surface such that when the firearm is in a loaded and cocked condition the timing surface retains the at least one lug in the second locking position; the locking arrangement being such that the length of the timing surface determines the delay between the discharge and unlocking of the at least one lug, as the locking slide is subjected to recoil induced movement relative the bolt head.

Preferably, said locked configuration of the locking arrangement is adapted to retain a cartridge in the cartridge chamber of the firearm; the predetermined time delay being sufficient for pressure to drop in the barrel of the firearm, thereby to minimize the ingress of gasses and other foreign material into the firing mechanism of said firearm.

Preferably, said bolt head of the firearm is adapted for sliding movement in a cylindrical action body housing the firing mechanism; the action body coaxial being with the barrel of the firearm.

Preferably, said at least one pivotally attached lug of the bolt head is biased into the retracted unlocked position when disengaged from said timing surface.

Preferably, said action body is provided with an annular recess; a wall of the recess adapted to engage with the at least one lug when the at least one lug is in the second extended locking position.

Preferably, said locking slide is adapted for sliding movement in the cylindrical action body; the locking slide being biased into a forward position within the action body by a recoil spring; forward sliding movement of the locking slide firstly driving the bolt head to the abutting engagement with the barrel, and secondly engaging with the at least one lug to pivotally rotate the lug into the second extended locking position with the wall of the annular recess.

Preferably, subsequently to a discharge, a rearward sliding movement of the locking slide is communicated to the bolt head, once the at least one lug has disengaged from the timing surface, such that the bolt head is retracted rearwards from its abutting engagement with the barrel.

Preferably, a firing pin of the firearm operates along apertures in the bolt head and the locking slide; the length of the firing pin arranged so that engagement of the locking pin with a primer of a cartridge is prevented unless the locking slide is in the forward position with the bolt head locked in the abutting engagement with the barrel.

BRIEF DESCRIPTION OF THE DRAWINGS

A preferred embodiment of the invention will now be described, by way of example only and with reference to the accompanying drawings wherein:

Figure 1 is a schematic cross-sectional side view of a recoil delay arrangement for a blowback or recoil operated weapon, according to the invention, the weapon being cocked, locked up and ready to fire.

Figure 2 is a schematic cross-sectional side view of the arrangement of Figure 1, wherein the weapon is shown after firing, in the initial stage of a recoil.

Figure 3 is a schematic cross-sectional view of the arrangement of Figure 1 and 2, wherein the bolt head has just been unlocked and the bolt assembly is about to recoil.

Figure 4 is a schematic cross-sectional side view of the arrangement of Figures 1 to 3, wherein the bolt assembly is partially recoiled.

Figure 5 is a schematic cross-sectional top view of the weapon of Figures 1 to 4, showing the cocking handle and the magazine. PREFERRED EMBODIMENTS OF THE INVENTION

In the preferred embodiment, the recoil operated weapon is in the form of firearm 1, a section of which is illustrated in Figures 1 to 5. The illustrated section of the firearm includes barrel 2 with sights, grips and heel plate (not shown). A cylindrical action body 3 is threaded to barrel 2. The firearm also includes a trigger assembly 4 having sear 5 that is screwed to action body 3. Magazine connection, ejector slots and stock tube, not shown, are fitted to action body 3. Bolt assembly 6 consists of the firearm's cocking handle 7 (visible in Figure 5), bolt head 8 and locking slide 9. Bolt head 8 includes spring washers 10, spring washer stop 11 and firing pin 12. Recoil return spring 13, polyurethane stop 14, rear recoil stop plug 15, its locking spring pin 16, locking lug 17, cartridge ejector 18 and extractor 19 are also part of bolt assembly 6. The bolt assembly is held together by cocking pin 20 and is arranged for sliding movement within action body 3.

To use the weapon, a trigger safety lever (not shown) is switched to "safe", the magazine with the cartridges is snapped and cocking handle 7 is pulled back. Upon release of handle 7, recoil spring 13 forces bolt assembly 6 forward, taking a cartridge from the magazine and loading it into cartridge chamber 21 in barrel 2. The firearm is thereby cocked, but is still on safety lock.

During the above forward movement, lock-up of bolt assembly 6 occurs when the recoil return spring 13 pushes front face of bolt assembly 6 hard against the barrel chamber face 25. Locking slide 9 is pushed by recoil spring 13 into engagement with bolt head locking lug 17, which is pivoted outwardly from behind the bolt head 8 so as to engage with an_angled wall 23 of an annular recess in the action body 3, thus preventing rearward movement of the bolt head. The forward movement also cocks the firing pin by the compression of spring washers 10 as cocking pin 20 is arrested by the cocking stop 24 of sear 5.

In the locked position shown in Figure 1, where the bolt head locking lug 17 pushes against angled wall 23 of the annular recess, the bolt head is positively sealed against the inner face 25 of barrel 2. The locking slide 9 under urging of the recoil spring 13 is then at its maximum forward position, limited by the shoulder of the timing surface engaging the outer end of the locking lug 17. When the firearm is fired, bolt head 8 is released and allowed to recoil only after a predetermined time delay, thus eliminating the penetration of foreign substances, such as discharge gasses and water vapour, into the action body during the cartridge discharge.

The process by which the time delay is implemented will now be explained. In order to fire the rifle, the safety lock must be unlocked and the trigger actuated to release firing pin 12. Firing pin 12 is driven forward by the compressed spring washers 10 to indent the cartridge primer and make it ignite, thus discharging the cartridge. When the cartridge is discharged, during the initial stage of recoil while the bullet moves up the barrel, locking slide 9 is driven rearwards by the force of recoil as shown in Figure 2. However, locking lug 17 initially prevents the rearward movement of bolt head 8. Only after the entire length of timing surface 26 is withdrawn from its engagement with locking lug 17, is the lug allowed to pivot back into the main bolt head body as, because of the rearward pressure on the bolt head, the angled face of the locking lug slides against angled wall 23. Thus, the pivoting movement of the lug into closed configuration allows the whole bolt assembly to recoil, as shown in Figure 3 and Figure 4. The time delay is typically adjusted so that the bolt head remains locked until the bullet exits the barrel and the pressure in the barrel reaches a desired low level.

The force driving the recoil of the bolt head, after it is unlocked, is the backwards inertia of the recoiling locking slide 9. At a particular point during its backward movement after the discharge, the slide engages locking pin 20, so that the movement is communicated to bolt head 8 as the firing pin is pulled backwards against spring washers 10, which in turn push against washer reaction ring 11. From this point on, the locking slide and the bolt head recoil together. Thus, the recoil of locking slide 9 is used to effect both the unlocking and the recoil of bolt head 8.

During the recoil of bolt assembly 6, the spent cartridge case is extracted from the cartridge chamber 21 and is ejected through a cocking handle slot (or alternative slot) as the bolt assembly moves rearward. The bolt assembly then reaches the fully recoiled position, with the recoil spring 13 and the polyurethane stop being fully compressed. After bolt assembly 6 is stopped from its rearward movement, it is then pushed forward by the compressed recoil spring 13 and compressed polyurethane, picking up another cartridge from the magazine and sliding said cartridge into the weapon's cartridge chamber 21 in front of the bolt assembly. Lock-up is again achieved in the same way as previously described and the firearm is ready to fire single shot, burst or automatic.

It is clear from the above description that the time delay, after which the entire bolt assembly 6 is allowed to recoil, is a function of the length of the timing surface 26. This length can be varied to suit various types of ammunition. One example is if the use of cartridges containing different charges or different projectiles, is desired. In addition, other factors can also be used to accommodate such a change. Such factors are the strength of the recoil return spring 13, the mass of the locking slide 9, the total mass of bolt assembly 6, the mass and velocity of bullet, the total mass of the weapon and whether or not residual gas pressure is used to increase bolt assembly recoil movement. A larger discharge is accommodated by using a longer delay surface, smaller mass of the locking slide or the total mass of the bolt assembly, or a smaller spring constant of the recoil spring.

In the above description the system was arranged so that the backwards momentum of the weapon, caused by the discharge, is used for unlocking the bolt head. However, a residual pressure from the discharge can also be used to assist the recoil of the bolt head, after it has been unlocked. One way to utilise some of the pressure created during cartridge discharge is by reducing the length of the time delay surface to reduce the delay time in order to allow unlocking of the system at different reference point with respect to the time of cartridge discharge.

It has to be noted here that, strictly speaking the term "recoil" refers to the backward movement of the weapon upon discharge of a cartridge. Thus, the delayed backwards movement of the bolt head is not strictly a "recoil". However, since this backward movement is ultimately caused by the recoil of the weapon, for simplicity and succinctness, this delayed backward movement of the bolt head here has also been called "recoil". Similarly, although the arrangement that is the subject of this invention relates to both the locking and the unlocking of the bolt head, for simplicity and easy of reference, it has been simply referred to as "locking arrangement". An additional feature of the above described arrangement is that firing pin 12 protrudes through an opening in bolt head 8 and is configured to protrude and be able to reach and discharge the cartridge only if the bolt head is substantially in a locked configuration. It will be apparent from Figure 2 in particular, that the firing pin 12 is of such a length that it would be arrested by the cocking stop 24 reaching the forward limit of the slots in locking slide 9, unless slide 9 is in the locking position of Figure 1. This ensures that the firearm is fired only if bolt assembly 6 is substantially locked, thus providing a consistent time delay.

Another feature of the disclosed system includes the fact that the sliding elements of the bolt assembly are designed to lock in line so that all clearances between abutting elements of the bolt assembly are minimised when the bolt head comes into the locked position. This allows large clearance between the sliding adjacent surfaces of the bolt- assembly and the action body while the bolt is moving inside the action body. Because of this, the system can operate with dirt and water inside the body and bolt area. Also, in this preferred embodiment of the invention, the in-line lock-up system does not have to have gas operated blow back pistons to move the bolt so as to turn the locking bolt head. Thus, there is no fouling of these parts, as they are not required to operate this system.

It should be understood that as the bolt head comes into the locked position the bolt assembly may cock the weapon such that it may fire again.

Further advantages of the system relate to the fact that the system has minimum number of parts, is easy to machine and simple to maintain. The system also offers substantial flexibility in relation to amendments to the structure of the firearm. For example, the cocking handle can be on the left or right, the magazine and cartridge ejection slots can be radially positioned almost anywhere and no separate hammer is needed to actuate the firing pin.

It is obvious from the above description, that the disclosed arrangement offers a relatively simple and reliable system for locking positively the barrel of a firearm for a particular length of time after a cartridge discharge, thus minimising the penetration of foreign substances into the firing mechanism of the weapon during and immediately after the discharge. It should be appreciated that the disclosed arrangement is not limited to the particular embodiments disclosed here, but also covers other arrangements using similar concepts. For example, while the preferred embodiment uses a single locking lug, two or more lugs can also be used. In addition, the lugs can be moved into locking engagement not only by the locking slide, but by any other part of the weapon that has a suitable relative movement with respect to the bolt head during the recoil.

Furthermore, although the above description of the invention relates to recoil operated firearms in which the differential masses of the firearm, as a whole, and the locking slide are utilised to effect the unlocking delay, the principles of the timing surface of the invention may equally be applied with other means of moving the locking slide.

Thus, for example, the activation of the locking slide rearwards may be effected by utilising the gas pressure generated in the barrel of the firearm at discharge, either by a gas tube providing blow-back of the slide, or a connecting rod operated by a gas actuated piston.

Again the movement of the slide may also be effected in firearms in which the barrel is slidably mounted and in which the recoil of the barrel rather than that of the firearm, as a whole, provides the recoil force driving the locking slide.

Finally, the principles of the timing surface may be applied to manually operated firearms, either single shot or pump action, where the slide is manually pulled back after discharge, then driven forward at reload to re-lock the bolt head.

The terms "comprising" and "including" (and their grammatical variations) as used herein are used in the inclusive sense of "having" and not in the exclusive sense of "consisting only of.

Claims

1. A bolt head locking arrangement for a recoil operated weapon where projectile is expelled by discharging a cartridge, the weapon comprising a longitudinal action body, a longitudinal barrel, the barrel being a part of or axially attached to the action body, and a bolt assembly, the bolt assembly being slidable within the action body so as to affect at least one of; loading cartridges in the barrel for discharging, discharging cartridges and extracting discharged cartridges; the bolt assembly comprising a bolt head, a locking slide and a firing pin, at least some of which being arranged for moving with respect to each other, wherein the arrangement further comprises locking means arranged so that, upon loading a new cartridge for discharging, the locking means positively lock the bolt head such that, for a predetermined amount of time after the loaded cartridge is discharged, the locked bolt head stops the cartridge from retreating into the action body, thus eliminating the penetration of pressure caused by the discharge into the action body, the locking means is substantially in an in-line configuration with the bolt assembly, and said locking means are arranged so that the recoil momentum of the weapon, caused by the discharge, is used for unlocking the bolt head, wherein the locking means are arranged so that, upon discharge of the cartridge, the locking slide recoils backwards and, once the bolt head is unlocked, the inertia of the locking slide facilitates the recoil of the bolt head.

2. The arrangement of claim 1, wherein the locking means are arranged so that, after the bolt head is unlocked, a residual of the gas pressure formed during the discharge is used for assisting with the recoil of the bolt head.

3. The arrangement of claim 1, wherein the locking means are arranged so that, upon loading a cartridge, a first abutment surface is brought into an abutment engagement with the locking means to bring them into an abutment engagement with a second abutment surface, thus locking the bolt head, the locking means being further arranged so that a predetermined time after the discharge of the cartridge, the first abutment surface is withdrawn from a locking engagement with the locking means, thus releasing them from the locking abutment engagement with the second abutment surface and allowing the bolt head to recoil.

4. The arrangement of claim 3, wherein the locking slide comprises a timing surface of predetermined length and the locking means comprise at least one locking lug that is engageable with the timing surface so as to move between open and closed configuration, wherein in the closed configuration the at least one lug is located within the cross-sectional area of the bolt head to allow the sliding movement of the head within the action body, while in open configuration the at least one lug extends beyond this cross-sectional area to abut with an abutment surface of the action body and prevent rearward movement of the bolt head, wherein in use; when the bolt assembly is moved forward to load a cartridge, the locking slide moves with respect to the bolt head so that the timing surface engages the at least one lug to push it into an open configuration, so that when the bolt head is moved fully forwardly, the bolt head is locked in a sealing engagement with the sealing inner surface of the barrel and in an abutment engagement with the abutment surface of the action body; and upon discharging the cartridge, the locking slide moves backwards, causing the entire predetermined length of the timing surface to withdraw from its engagement with the at least one lug and allow the at least one lug to move into closed configuration, thus unlocking the bolt head and allowing it to recoil.

5. The arrangement of claim 4, wherein at least one of the following parameters can be changed to adjust the time delay, during which the bolt head is locked, so as to allow the weapon to discharge a cartridge having different charge characteristics or projectile mass; the length of the timing surface; the mass of the locking slide, the bolt head, the bolt assembly or the mass of the entire weapon; the mechanical characteristics of a recoil spring used to move the bolt assembly forwards after a recoil.

6. The arrangement of claim 5, wherein the following parameters can be changed to adjust the time delay, during which the bolt head is locked, so as to allow the weapon to discharge a cartridge having different charge characteristics or projectile mass, in the following manner; increasing the length of the timing surface to allow for larger charge to be used; decreasing the mass of the locking slide, the bolt head, the bolt assembly or the mass of the entire weapon to allow for larger charge to be used; to reduce the spring constant of the recoil spring to allow for larger charge to be used.

7. The arrangement of any one of the preceding paragraphs, wherein the firing pin is arranged to be able to discharge a cartridge only if the bolt head is substantially in a locked configuration.

8. The arrangement of claim 7, wherein the firing pin is arranged to protrude through an opening in the bolt head so that, when the bolt head is not in a locked configuration, the firing pin is unable to reach the cartridge and effect a discharge.

9. A method for locking and unlocking a bolt head in a recoil operated weapon which expels projectiles by discharging a cartridge, where at least one of loading cartridges for discharging, discharging cartridges and extracting discharged cartridges is assisted by a bolt head assembly including a bolt head, the method comprising the step of locking, upon loading a new cartridge for discharging, the bolt head in a substantially in-line configuration such that, for a predetermined amount of time after the loaded cartridge is discharged, the locked bolt head prevents the cartridge from retreating into the action body, thus eliminating the penetration of pressure caused by the discharge into the action body, and the recoil momentum of the weapon, caused by the discharge, is used for unlocking the bolt head, and said method further comprising the step of allowing a member of the bolt head assembly, the member being engageable with the bolt head, to recoil, upon discharge of the cartridge, the inertia of the member being used to, upon unlocking of the bolt head, facilitate the recoil of the bolt head. . ^•

10. The method of claim 9, wherein, after the bolt head is unlocked, a residual of the gas pressure, formed during the discharge, is used for assisting with the recoil of the bolt head.

11. The method of claim 9, wherein locking of the bolt head is arranged by providing a first abutment surface that, upon loading a cartridge, is brought into an abutment engagement with locking means to bring them into an abutment engagement with a second abutment surface, thus locking the bolt head, unlocking of the bolt head a predetermined delay time after the discharge of the cartridge being facilitated by withdrawing the first abutment surface from the locking engagement with the locking means, thus releasing the locking means from the locking abutment engagement with the second abutment surface and allowing the bolt head to recoil.

12. The method of claim 11, wherein the method further includes the step of arranging so that, after a discharge, the first abutment member recoils immediately, so that its predetermined length defines the duration of engagement between the first abutment surface and the locking means, thus also defining the predetermined delay time of the recoil of the bolt head.

13. The method of claim 12, wherein, to allow the weapon to discharge a cartridge having different charge characteristics or projectile mass, the method comprises the step of adjusting the time delay, during which the bolt head is locked, by changing at least one of the following parameters; the length of the timing surface; the mass of the bolt head, the bolt assembly or the mass of the entire weapon; the mechanical characteristics of a recoil spring used to move the bolt assembly forwards after a recoil.

14. The method of claim 13, wherein to allow the weapon to discharge a cartridge having different charge characteristics or projectile mass, the method comprises the step of adjusting the time delay, during which the bolt head is locked, by changing at least one of the following parameters in the following manner; increasing the length of the timing surface to allow for larger charge to be used; decreasing the mass of the locking slide, the bolt head, the bolt assembly or the mass of the entire weapon to allow for larger charge to be used; to reduce the spring constant of the recoil spring to allow for larger charge to be used.

15.. The method of any one of claims 9 to 14, the method further including the step of arranging a cartridge to be discharged only if the bolt head is substantially in a locked configuration.

16. The method of claim 15, wherein a firing pin is arranged to protrude through an opening in the bolt head so that, when the bolt head is not in a locked configuration, the firing pin is unable to reach the cartridge and effect a discharge.

17. A locking arrangement for a bolt head of a recoil operated firearm having a barrel; wherein in locked configuration, the locking arrangement is adapted to retain the bolt head of the firearm in abutting engagement with the barrel for a predetermined time delay subsequent to discharge of the firearm; the locking arrangement comprising at least one lug pivotally attached to the bolt head; the at least one lug being operable between a first retracted unlocked position and a second extended locking position; the locking arrangement further comprising a locking slide provided with a timing surface such that when the firearm is in a loaded and cocked condition the timing surface retains the at least one lug in the second locking position; the locking arrangement being such that the length of the timing surface determines the delay between the discharge and unlocking of the at least one lug, as the locking slide is subjected to recoil induced movement relative the bolt head.

18. The locking arrangement of claim 17, wherein the locked configuration of the locking arrangement is adapted to retain a cartridge in the cartridge chamber of the firearm; the predetermined time delay being sufficient for pressure to drop in the barrel of the firearm, thereby to minimize the ingress of gasses and other foreign material into the firing mechanism of said firearm.

19. The locking arrangement of claim 17, wherein the bolt head of the firearm is adapted for sliding movement in a cylindrical action body housing the firing mechanism; the action body coaxial being with the barrel of the firearm.

20. The locking arrangement of claim 17, wherein the at least one pivotally attached lug of the bolt head is biased into the retracted unlocked position when disengaged from said timing surface.

21. The locking arrangement of claim 17, wherein the action body is provided with an annular recess; a wall of the recess adapted to engage with the at least one lug when the at least one lug is in the second extended locking position.

22. The locking arrangement of claim 21, wherein the locking slide is adapted for sliding movement in the cylindrical action body; the locking slide being biased into a forward position within the action body by a recoil spring; forward sliding movement of the locking slide firstly driving the bolt head to the abutting engagement with the barrel, and secondly engaging with the at least one lug to pivotally rotate the lug into the second extended locking position with the wall of the annular recess.

23. The locking arrangement of claim 17, wherein, subsequently to a discharge, a, rearward sliding movement of the locking slide is communicated to the bolt head, once the at least one lug has disengaged from the timing surface, such that the bolt head is retracted rearwards from its abutting engagement with the barrel.

24. The locking arrangement of claim 17, wherein a firing pin of the firearm operates along apertures in the bolt head and the locking slide; the length of the firing pin arranged so that engagement of the locking pin with a primer of a cartridge is prevented unless the locking slide is in the forward position with the bolt head locked in the abutting engagement with the barrel.

25. The locking arrangement of claim 1, wherein the unlocking and/or the recoil of the bolt head if effected by utilising gas pressure generated in the barrel of the firearm at discharge, either by a gas tube providing blow-back of the slide, or a connecting rod operated by a gas actuated piston.

26. The locking arrangement of claim 1, wherein the barrel is slidingly mounted, so that the unlocking and/or the recoil of the bolt head is facilitated by the recoil of the barrel.

27. The locking arrangement of claim 1, wherein the firearm is a single shot or a pump action manually operated firearm and wherein the unlocking and/or the recoil of the bolt head is effected manually.