RECEIVER SYSTEM FOR A BOLT ACTION FIREARM

Abstract

Receiver system for a bolt action firearm, comprising: a receiver comprising a forward end adapted to receive a barrel and a rearward end arranged to receive a breech bolt in a boltway provided in said receiver; a breech bolt adapted to slide linearly in said boltway and to lock to said receiver by rotation when said breech bolt is in a closed position; a buttstock interface block attached at a rearward end of said receiver and adapted to interface with said stock; a trigger mechanism provided in said buttstock interface block and arranged to cooperate with a cocking piece 31 carried by a striker provided in said breech bolt.

Claims

1-12. (canceled)

13. Receiver system for a bolt action firearm, comprising: a receiver comprising a forward end adapted to receive a barrel and a rearward end arranged to receive a breech bolt in a boltway provided in said receiver; a breech bolt adapted to slide linearly in said boltway and to lock to said receiver by rotation when said breech bolt is in a closed position; a buttstock interface block attached at a rearward end of said receiver and adapted to interface with said stock; a trigger mechanism provided in said buttstock interface block and arranged to cooperate with a cocking piece carried by a striker provided in said breech bolt.

14. Receiver system according to claim 13, wherein said trigger mechanism is arranged to retain said cocking piece and said striker in a cocked position by means of a sear and to release it in response to a predetermined pressure on a trigger.

15. Receiver system according to claim 13, wherein said receiver comprises at least one rail on a lower side thereof, said rail being adapted to interface with said buttstock interface block.

16. Receiver system according to claim 13, wherein said buttstock interface block is fixed to said receiver by means of at least one fixing bolt.

17. Receiver system according to claim 13, wherein said receiver comprises a locking shoulder situated rearward of said boltway.

18. Receiver system according to claim 17, wherein said breech bolt comprises at least one locking surface adapted to interact with said locking shoulder, said locking surface being adjacent to a bevelled surface arranged to cooperate with said locking shoulder so as to provide a mechanical advantage when rotating said breech bolt towards a locked position.

19. Receiver system according to claim 18, wherein said breech bolt comprises a first primary extraction cam arranged to interact with a second primary extraction cam provided on a rearward-facing surface of said receiver when said bolt is turned towards its fully unlocked position.

20. Receiver system according to claim 18, wherein said breech bolt comprises two locking surfaces arranged symmetrically such that by rotating said breech bolt in a first direction about its longitudinal axis a first of said locking surfaces can be brought into engagement with said locking shoulder, and by rotating said breech bolt in a second direction opposite to said first direction about its longitudinal axis a second of said locking surfaces can be brought into engagement with said locking shoulder.

21. Receiver system according to claim 18, wherein said breech bolt and said locking shoulder are adapted so as to define: an unlocked position in which said at least one locking surface is clear of said locking shoulder; a locked position in which a locking surface is in contact with said locking shoulder and in which said cocking piece is free to travel forwards to its fullest extent; and a safety position between said unlocked position and said locked position in which a locking surface is in contact with said locking shoulder and in which said cocking piece is prevented from traveling forwards to its fullest extent.

22. Receiver system according to claim 21, further comprising a detent system adapted to maintain said breech bolt in each of said positions.

23. Receiver system according to claim 22, wherein said detent system comprises a spring-loaded plunger mounted in at least one of said receiver and said buttstock interface block, said plunger being arranged to cooperate with a plurality of detent surfaces and/or notches provided on said breech bolt.

24. Firearm comprising: a receiver system according to claim 13; a barrel fixed to said forward end of said receiver; and a buttstock interfacing with or integral with said buttstock interface block.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Further details of the invention will become apparent in the following description, with reference to the drawings in which:

[0028] FIG. 1 is a schematic side view of a firearm comprising a receiver system according to the invention;

[0029] FIG. 2 is a schematic side view of a receiver system according to the invention;

[0030] FIG. 3 is a lateral cutaway view of the receiver system of FIG. 2;

[0031] FIG. 4a is a bottom view of the receiver and a top view of the buttstock interface block;

[0032] FIG. 4b is a cross-sectional view of the interface between the receiver and the buttstock interface block, along the line A of FIG. 3;

[0033] FIG. 5 is a partial side view of the bolt;

[0034] FIG. 6 is a rear view of the bolt in various positions, namely 0°, 20°, 45° and 90° from its unlocked position;

[0035] FIGS. 7a-g are partially cutaway side views of the bolt in various positions, respectively unlocked and partially withdrawn; at its forward position prior to rotation; rotated by 45° from its unlocked position; locked to the receiver at 90° from its unlocked position with the striker cocked; as per the previous orientation but illustrating the striker also in its fired position; at 45° to its unlocked position with the striker in its recocked position; returned to its unlocked position; and

[0036] FIG. 8 is a rear cross-sectional view of the interaction between the detent plunger and the flats and notches on the bolt.

EMBODIMENT OF THE INVENTION

[0037] FIG. 1 illustrates schematically a bolt-action firearm 1 comprising a receiver system 3 according to the present invention. In the present specification, “forward” and “front” are used to indicate a direction in which the barrel 7 extends from the receiver 5, towards its muzzle, which is also the direction of projectile travel. “Rearward” and “rear” are used to indicate the opposite direction, that is to say towards the shoulder of the firer. “Upper”, “lower”, “underside” and similar are used with reference to the conventional orientation of the firearm in use.

[0038] The receiver system 3 is illustrated in more detail in FIGS. 2-4b and comprises, as is generally known, a receiver 5 of broadly tubular form, provided with a rifled or smooth-bored firearm barrel 7 attached at a forward end thereof and provided with an appropriate bore and chambering. This fixation can be carried out by threading (e.g. by means of the barrel threads 5c provided at the front end of the receiver 5 as illustrated in FIG. 3), pinning, shrink-fitting or by any other known means. As illustrated, the main portion of the receiver has a circular cross-section, but it is equally possible to utilise a rectangular, square or otherwise polygonal outer cross-section.

[0039] The receiver 5 is bored out longitudinally so as to define a boltway 5f (see FIGS. 3 and 4b) adapted to receive the bolt body 9a of a breech bolt 9, of the turnbolt type, such that the breech bolt 9 can slide linearly therein parallel to the axis of the barrel 7, and can rotate about its longitudinal axis to lock to the receiver 5 at the forward end of its stroke. The breech bolt 9 comprises a striker 33 (see FIGS. 7a-g) fixed to a cocking piece 31 and adapted to strike a primer of a cartridge provided in the chamber of the barrel 7 by means of a firing pin 33a (see FIGS. 5 and 7a), the striker 33 being driven by a spring (not illustrated) as is generally known. The spring may be a coil spring, a stack of conical or dished washers (so-called “Belleville washers”), or any other known type.

[0040] The firearm is provided with a trigger mechanism 11 arranged to retain the cocking piece 31 and striker 33 in a cocked position by means of a sear 37, and to release it to strike the primer in response to a predetermined pressure on a trigger 11a, as is generally known.

[0041] The barrelled receiver 5 is supported in a stock 13, which may be of any convenient shape, and may be a so-called one-piece stock in which at least part of the buttstock 13a is integral with at least part of the forend 13b, or a so-called two-piece stock in which the buttstock 13a and forend 13b are distinct parts not directly linked to each other. The stock 13 can be made of multiple subcomponents, and can be provided with attachment points for accessories (bipods, downgrips, sling mounting points, monopods, lights, lasers and so on) as is generally known.

[0042] The firearm 1 as illustrated comprises a magazine 15 of any convenient type removably attached to the underside of the receiver 5 and adapted to hold unfired cartridges such that they can be fed into the chamber by reciprocation of the bolt 9. Alternatively, the system 3 may have an internal non-removable magazine, or may be single-shot and not be provided with a magazine. As illustrated, the receiver comprises an ejection port 5a on an upper side thereof, so as to permit ejecting empty cases and unfired live rounds. Alternatively, one or more ejection ports 5a can be provided on one or both side faces of the receiver at any convenient angle, or can even be omitted in the case in which the cartridge is clipped into the bolt face prior to insertion of the bolt 9 into the receiver 5 in a single-shot configuration, as is already the case in certain precision rifles.

[0043] The core of the first aspect of the invention lies in the overall construction of the receiver system 3, and how it is adapted to interface with the stock 13. Standard, non-relevant features such as rails or mounts for sights or similar are well known to the skilled person and hence need not be discussed.

[0044] The receiver system 3 does not comprise a conventional recoil lug. Instead, it is constructed of three separate parts: the receiver 5, a forend interface block 17, and a buttstock interface block 19, this latter also housing the trigger mechanism 11, notably in the interior thereof. The buttstock interface block 19 is adapted to interface with a buttstock 13a, whether this is integrated with a forend 13b or not.

[0045] The forend interface block 17 is attached at the front of the receiver 5 on the underside thereof, by means of a dovetail rail 5b or other suitable rail cooperating with a further rail 17a of complementary form provided on the upper surface of the forend interface block 17. As illustrated in FIG. 3, the forend interface block 17 is attached to the front end of the receiver, adjacent to the barrel threads 5c, by means of a fixing bolt 21 or any other convenient means arranged to push the forend interface block 17 away from, or to pull it towards, the receiver 5, thereby tensioning the dovetail interface 5b, 17a. As can be seen from FIG. 4a, the rail 5b on the receiver is male and that provided on the forend interface block 17 is female, however the opposite configuration is equally possible, as are other equivalent arrangements and rail shapes. Furthermore, instead of rails, lugs and corresponding recesses can be provided in the receiver 5 and forend interface block 17, or other equivalent means to positively interface the two parts 5, 17 can be provided, such as bolts or similar attaching these two components together in any convenient manner.

[0046] The forend interface block 17 can be fixed into a groove of complementary shape inletted into the forend 13b of the stock 13, the fixation being by means of bolts, screws, bonding, welding (in the case in which the stock is made of metal or contains a metal chassis), or any other convenient means, and keeps the forend 13b in place on the front of the receiver system 3 via these fixing means. Furthermore, the rear face of the forend interface block 17 may also comprise a guide such as a groove or rail for guiding a magazine, and/or retention means for releasably retaining such a magazine.

[0047] However, other means for attaching the forend 13b to the receiver 5 and/or barrel 7 are also possible, and are well-known to the skilled person. This applies whether the forend 13b and buttstock 13a are directly attached to each other, and also when the stock 13 comprises a separate buttstock 13a and forend 13b which are not directly connected together.

[0048] The buttstock interface block 19 is likewise mounted to the rear of the receiver 5 by means of a further rail 5d provided on the underside of this latter, which cooperates with a complementary rail 19a provided on the upper surface of the buttstock interface block 19. These two rails 5d and 19a can have the same or different forms to the rails 5b and 17a respectively, or may have different forms, and a pair of fixing bolts 23 urge mounting studs 24 firmly against edges of corresponding openings in the receiver 5, pushing the dovetails 19a, 5d apart and thereby securely attaching the receiver 5 to the buttstock interface block 19. As an alternative, it is also possible for fixing bolts 23 to engage with corresponding threaded holes provided in the receiver 5, or with separate threaded elements provided in the receiver 5 so as to pull the receiver 5 towards the buttstock interface block 19. The same considerations for alternatives to rails as discussed above in respect of the forend interface block 17 apply equally here, and again the front end of the buttstock interface block 19 may also comprise a guide for guiding a magazine, and/or retention means for releasably retaining such a magazine.

[0049] In order to transmit recoil force to the buttstock 13a, the rear face 19b of the buttstock interface block 19 can simply abut a corresponding shoulder provided in the stock 13. This shoulder can be reinforced with a pin 25, arranged to abut a corresponding notch 19c provided in said rear face 19b. Alternatively, the pin 25 may be flat-faced so as to provide a planar abutment surface with respect to said rear face 19b, and may simply contact this latter or engage with a correspondingly-shaped notch 19c.

[0050] In the case in which the buttstock 13a is not integrated with the forend 13b (i.e. in the case generally known as a “two-piece stock”), the buttstock 13a can be fixed to the buttstock interface block 19 by any suitable means, such as bolts, pins or similar, or may simply be integrated therewith in a monobloc fashion, together with a pistol grip (if present). Likewise, the forend 13b may be integrated with the forend interface block 17 in a unitary construction.

[0051] In view of the construction as described above, both the forend fixing block 17 and buttstock interface block 19 can be constructed very simply, using conventional tooling on conventional 3-axis milling machines using rotary cutters, whether manually-operated or CNC-operated. Furthermore, the receiver 5 can be turned on a simple lathe, and then its other features as described above can be milled on a conventional 3-axis milling machine with appropriate rotary cutters.

[0052] This aspect of the invention, considered broadly, places no particular constraints on the nature of the locking system or the bolt, which can be of any convenient type and can be either front or rear locking. However, the illustrated construction is particularly simple and efficient to manufacture, as will become clear in the following description. Furthermore, as is generally known, rear locking results in a relatively short bolt travel, ease of cleaning, and so on.

[0053] Consulting FIG. 3, it can be clearly seen that the boltway 5f provided in the receiver for receiving for the body of the bolt 9 is cylindrical and extends in a longitudinal direction, and can hence be lathe bored or drilled and reamed. This is a consequence of the locking arrangement, in which one or more locking surfaces 9b (commonly known as “lugs”) are provided on a widened portion 9d of the bolt 9 which serves as the base or root of the bolt handle 9c, whether this latter is integral with the bolt 9c or is a separate part attached thereto. The locking surface 9b cooperates with a locking shoulder 5g, which extends upwards from the inner lower face of the rear end of the receiver perpendicular to the longitudinal axis of the bolt 9, and hence permits locking the bolt 9 when the handle 9c has been rotated such that the locking surface 9b engages with the locking shoulder 5g. This engagement resists the forces generated upon firing.

[0054] Since the locking shoulder 5g is situated to the rear of the entirety of the boltway 5f, it is outside of the tubular portion of the receiver 5. As a result, it is easily machinable with conventional rotary cutters on a 3-axis milling machine, and presents several further advantages, as will become clear below. It should also be noted that the locking shoulder 5g may be provided as a separate part mounted on the receiver 5. In such a case, various dimensions of locking shoulder 5g can be provided in order to easily adjust headspace, as is generally known. Alternatively, headspace can be set in any one of a plurality of conventional manners, such as careful individual machining of the chamber, timing washers of appropriate thicknesses situated between the barrel shoulder and the receiver 5, Savage-type breeching-up nuts, a separate threaded piece provided in the receiver 5, or similar.

[0055] FIG. 5 illustrates part of the bolt 9 in greater detail, FIG. 6 illustrates a part of the bolt 9 viewed from the rear in various positions, and FIGS. 7a-7g illustrate in partially cutaway side view the interaction between the bolt 9 and the rear portion of the receiver 5. Since it is unnecessary to repeat the reference signs on each part of FIGS. 6 and 7, they have only been included on the left-most diagram of FIG. 6, and on FIG. 7a.

[0056] As noted above, the locking surface 9b is formed on a wider section 9d of the bolt 9, which is wider than the part thereof which enters into the boltway 5f and into which the bolt handle 9c is fitted. Indeed, two such locking surfaces 9b are provided symmetrically on either side of said wider section 9d, although only one is required in respect of this aspect of the invention.

[0057] In the position indicated as 0° on FIG. 6, the locking surfaces 9b are clear of the summit of the locking shoulder 5g in the receiver 5, illustrated by the line R-R. The bolt 9 can hence be moved rectilinearly so as to feed a cartridge into the chamber of the barrel 7, or to extract a spent or live cartridge therefrom, as is generally known and is likewise represented in the positions illustrated in FIGS. 7a and 7b. When the bolt 9 is pushed fully forward without rotating, a bevelled surface 9f overlaps the locking shoulder 5g, and a first primary extraction cam 9m abuts a corresponding second primary extraction cam 5h provided on a rearward-facing surface 5s of said receiver, this second primary extraction cam 5h hence serving as a forward bolt stop. In the illustrated embodiment, both of these primary extraction cams 9m, 5h are formed as dome-headed studs fitted into the bolt 9 and receiver 5 respectively, but other forms of cam are also possible, such as wedge-shaped cams.

[0058] When the bolt 9 is then rotated a certain angle clockwise, illustrated as the approximately 20° position in FIG. 6, this brings the bevelled surface 9f the locking surface 9b into contact with the locking shoulder 5g, so as to provide a degree of mechanical advantage when closing the bolt 9 on a damaged, dirty or “sticky” cartridge or chamber.

[0059] Further rotation of the bolt handle 9c, as illustrated in the 45° position of FIG. 6 and on FIG. 7c, causes positive engagement between the locking surface 9b and the locking shoulder 5g, as can clearly be seen from the fact that a portion of the locking surface 9b which is perpendicular to the axis of the bolt 9 is below the line R-R on FIG. 6 and is clearly in engagement on FIG. 7c, and the bolt 9 is hence mechanically locked. This position can be used as a safety position, as will be described below, and other angles such as between 20° and 70° are also possible in respect of this safety position. However, this intermediate safety position is not essential to the present aspect of the invention.

[0060] Further rotation to the 90° position fully locks the bolt 9 to the receiver 5, and frees the passage of the cocking piece 31 as is generally known in bolt-action rifles. Since many variations of blocking means arranged such that the cocking piece 31 can only travel fully forward and cause the firing pin 33a to strike the primer of a cartridge are known in the art, they do not need to be discussed in detail here, although a discussion of the particularities of the present construction is discussed below in the context of the safety system.

[0061] In order to maintain the breech bolt 9 in each of its (quasi-)stable angular positions against undesired rotation, a detent system is provided. This system comprises a plunger 27 which is mounted in the buttstock interface block 19 and in the receiver 5, crossing from the former into the latter. The plunger 27 is pressed against the underside of the bolt 9 by means of a spring 27a. The bolt body 9a is provided with a number of detent flats 9g, 9h and notches 9i, which are situated proximate to the wider section 9d and are best visible on FIGS. 7a-g and 8. Other forms of detent surfaces other than flats and notches are of course possible.

[0062] In the 0° position, i.e. with the bolt handle 9c vertical, the plunger 27 presses against a first detent flat 9g, which may also extend the length of the bolt body 9a at least over the distance over which contact will be maintained between the plunger 27 and the bolt body 9a. This first flat 9g hence positively defines the unlocked position of the bolt 9. Rotation of the bolt 9 when it is not in the forward position is prevented by means of the head 24a of the frontmost mounting stud 24 (see FIGS. 3, 4b and 7a), which interacts with a flat provided to this purpose on the bolt body 9a. Alternatively, in a non-illustrated variant, the head 24a of this stud 24 can penetrate into a groove provided in the underside of the bolt body 9a, or undesired rotation can be prevented by other similar known means. The head 24a may also act as a safety lug in the case in which a shoulder in the bolt body is situated forward of the head 24a when the bolt 9 is in its locked position. In such an arrangement, if the locking surface 9b fails, the stud 24 retains the bolt and prevents it from leaving the receiver 5.

[0063] In the 45° position, the plunger 27 presses against a further detent flat 9h, which likewise serves to maintain the bolt 9 in this position. In the 90°, fully locked position, the plunger presses into a groove 9i, which serves to maintain it in this position against undesired rotation, without providing excessive resistance to a deliberate rotation.

[0064] After firing a cartridge, when the bolt 9 is rotated back towards the 0° position, the two primary extraction studs 9m, 5h enter into contact and generate a backwards movement of the bolt 9 by camming action, the bevel 9f providing sufficient clearance such that the locking surface 9b can clear the locking shoulder 5g.

[0065] In respect of the safety system of the present construction, as noted above, the intermediate approximately 45° bolt position of FIGS. 6, 7c and 7f serves as a safety position.

[0066] In the present construction, the firing pin 33a is actuated by a cocking piece 31, affixed on the extremity of a rod-shaped striker 33 as is generally known. The firing pin 33a may be integral with this striker 33, as in a Lee-Enfield, Mauser or similar system, or may be a separate part as in e.g. a Swiss K31 type rifle. The cocking piece 31 is surrounded and guided by a shroud 35, which is shaped so as to maintain the cocking piece 31 in a vertical position irrespective of the angle of the bolt 9 with respect to the receiver 5.

[0067] The rear end of the bolt 9 comprises a set of safety lugs 9n, which serve to only permit the cocking piece 31 to travel sufficiently far forward to fire a cartridge when the bolt handle 9c is fully locked, serve to block such travel in all other angular positions thereof, and also serve to prevent undesired rotation of the cocking piece 31 with respect to the bolt 9 when this latter is in an open position. The exact shape of the safety lugs 9n to carry this out is unimportant, and need not be described in detail since a great number of variations are possible which exhibit the functionality described below. The safety lugs 9n are also be arranged to withdraw the striker a certain distance when the bolt 9 is unlocked after firing, as is generally known, by means of a cam surface 9p which interacts with the cocking piece 31 as will be described further below.

[0068] FIG. 7a illustrates the bolt in the out of battery position. The cocking piece 31 is in contact with the safety lugs 9n, and hence cannot go sufficiently forward to fire a cartridge. In this position, the cocking piece 31 is prevented from rotating with respect to the bolt 9 by means of a pair of symmetrical shoulders 9q, which define a notch 9r (see FIG. 6) in which it rests. Upon closing the bolt as illustrated in FIG. 7b, the cocking piece 31 engages with a sear 37 (see FIG. 3), and the user can rotate the bolt 9 as described in the context of FIG. 6. It should be noted that the present construction is a “cock-on-open” system with a relatively short striker travel, but it is also possible for the sear 37 to be positioned further to the rear such that the system is a “cock-on-closing” system in which the firing pin spring is compressed on the forward movement of the bolt 9.

[0069] In the 45° position of FIG. 7c, the cocking piece 31 rises onto one of the shoulders 9q of the safety lugs, and is hence prevented from falling to strike a cartridge.

[0070] In the 90° “locked” orientation of the bolt handle 9c (see FIG. 7d), the safety lugs 9n are clear of the path of the cocking piece 31, which hence rests on the sear 37. When the trigger 11a is pulled in this position, the cocking piece 31 can drop, as illustrated in FIG. 7e, causing the firing pin 33a to protrude and strike the primer of a cartridge. The exact nature of the trigger mechanism 11 is unimportant to the present invention and hence need not be described in detail, innumerable versions of such mechanisms being known to the skilled person.

[0071] After dropping the cocking piece, upon rotating the bolt handle 9c back towards the 45° position as shown in FIG. 7f, a cam surface 9p formed by the safety lugs 9n withdraws the cocking piece 31 a certain distance such that the firing pin 33a is withdrawn from contact with the fired cartridge, back into contact with the shoulder 9q. Finally, when the bolt 9 is rotated back to the initial position, first primary extraction cam 9m and second primary extraction cam 5h interact to withdraw the bolt 9 slightly to effect primary extraction, and the cocking piece 31 falls back into the notch formed between shoulders 9q. The bolt 9 can be withdrawn and the cycle can repeat.

[0072] Another advantage of the receiver 5 construction of the present invention is that it can be arranged to be fully ambidextrous without requiring any modification whatsoever. To this end, the bolt 9 is constructed symmetrically about a plane intersected by the bolt handle 9c, and hence comprises two locking surfaces 9b and two bevels 9f arranged symmetrically either side of said plane. As a result, the bolt handle 9c can be turned either clockwise or anticlockwise when it is being locked.

[0073] It is also for this reason that the extractor 39, of conventional form, is arranged such that it is oriented upwards when the bolt 9 is unlocked, and why the ejection port 5a is arranged on the top of the receiver 5 as in a Swiss K11 or K31 system. For similar reasons, the ejector 29 is arranged underneath the bolt 9, and is of the vertically-sliding type known in the aforementioned K31 rifle. This ejector 29 is arranged to protrude from a corresponding slot in the bolt face when the bolt 9 is in its fully retracted position subjected to a force provided by a spring 29b tending to push the ejector 29 in the direction of the bolt body 9a. The ejector 29 furthermore carries a bolt stop 29a arranged such that, upon retraction of the bolt, a shoulder in the bolt 9 hits the bolt stop 29a to prevent further rearward movement of the bolt 9. In the case in which the ejection port 5a is located on the side of the receiver, the extractor 39 can be positioned as appropriate in the bolt body 9a, and the ejector may be a conventional plunger type situated in the face of the bolt 9 diametrically opposite to the extractor 39 as is well known in the art and need not be described further. Indeed, such a plunger-type ejector can also be used with substantially vertical ejection.

[0074] However, as noted above, the bolt does not need to be ambidextrous in this manner, in which case only a single locking surface 9b is required. Furthermore, it is possible to keep the ambidextrous capability while turning the bolt handle 9c down, for instance by arranging this latter as a separate part which can be attached to the remainder of the bolt 9 in either orientation for left-handed or right-handed use.

[0075] Furthermore, it is noted that the various angles of the bolt handle 9c in various positions are not to be construed as limiting. For instance, the unlocked position does not have to be 0° from the vertical, but can be at any convenient angle, particularly when the bolt 9 is not arranged to be ambidextrous. Likewise, the locked position does not have to be 90° from the vertical, but can be any desired angle such that there is sufficient mating area between the locking surface 9b on the bolt 9 and the locking shoulder 5g on the receiver 5 in order to safely resist the forces generated on firing. In the case in which the unlocked position is not vertical and the firearm 1 is intended to be used ambidextrously, multiple second primary extraction cams 5h can be provided as desired.

[0076] As a final note, the above-described construction is very simple, with relatively few edges and relatively few interior corners, which makes machining and subsequent gauging for quality control purposes very simple (few gauges, relatively little gauging time). The relative lack of interior corners also makes cleaning simple for the user.

[0077] Although the invention has been described in terms of a specific embodiment, variations thereto are possible without departing from the scope of the invention as defined in the appended claims.