Firearm receiver assembly and firearm receiver tensioning arrangement

Abstract

A firearm receiver assembly (1) comprises a lower receiver (2) and an upper receiver (3) wherein one of said receivers has a forward facing surface (36a) and the other receiver has a rearward facing surface (26b) and an adjustable length receiver tensioning assembly (50) which is in contact with both said forward facing surface (36a) and said rearward facing surface (26b) and is operable to move said forward facing surface (36a) and said rear facing surface (26b) towards each other or away from each other to reduce play between the upper receiver (3) and lower receivers (2).

Description

[0001] FIREARM RECEIVER ASSEMBLY AND FIREARM RECEIVER TENSIONING ARRANGEMENT TECHNICAL FIELD

[0002] The present invention relates generally to firearms, and more particularly to a firearm receiver assembly and a firearm receiver tensioning assembly for securing upper and lower receiver portions of a firearm together to reduce relative movement between them.

[0003] BACKGROUND

[0004] The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

[0005] As known in the prior art firearms such as the AR-15 include a separate upper receiver and lower receiver that are secured together via a pivot pin along the front ends, and a takedown pin that is removably positioned through apertures along the back ends of the receivers. With regard to popular rifle types, many different manufacturers produce components which are designed to a standard specification which can be interconnected with other components to form a fully assembled firearm. Owing to the standard specification, it is possible to assemble the firearm using upper and lower receivers that are manufactured by the same or different companies. Depending on the specific tolerances of the upper and lower receiver halves, a resulting gap can be formed along the mating surfaces, and it is not uncommon for there to be a certain amount of independent movement between the receiver halves when assembled. This movement (often referred to as “slop”, “wriggle” or “play”) is undesirable, as it can misalign the bolt and cartridge, thereby reducing the reliability of the firearm. Play can also occur due to wear or manufacturing tolerances of the takedown and pivot pins or the apertures which receive them. There can be “longitudinal horizontal play” which is play between the receivers in the fore and aft directions, “lateral horizontal play” which is side to side play between the receivers with respect to each other, “vertical play” in which the upper and lower receivers, or portions thereof, can move up and down with respect to each other, and combinations of these horizontal and vertical plays. Accordingly, itwould be beneficial to provide a firearm receiverwith an adjustable receiver tensioning assembly that can reduce or eliminate some or all of said undesirable movement between upper and lower receiver halves.

[0006] It is known in the prior art US10859332 to provide a lower receiver body of an AR-15 with a cam arrangement attached to a takedown pin, the cam arrangement being adapted to impart a downward and rearward force onto a takedown pin and an upper receiver traversed by the takedown pin. A problem with such an arrangement is that it comprises many moving parts and substantial modifications to at least the lower receiver.

[0007] SUMMARY OF THE INVENTION

[0008] The present invention is directed to a firearm receiver assembly with an adjustable receiver tensioning assembly which is simpler than those known in the prior art. One embodiment of the present invention can include a lower receiver body for assembling with an upper firearm receiverand other firearm components. The lower receiver body includes a pair of opposed takedown pin openings that are positioned along each side of the receiver body and an adjustable length receiver tensioning assembly for clamping the upper receiver to the lower receiverwith a vertically downwards force and / or horizontal force.In an embodiment the upper receiver body comprises a takedown pin receiving block with a transverse bore which is aligned with the takedown pin opening in the lower receiver when assembled.

[0009] A takedown pin can transverse the pair of takedown pin openings and the bore in the takedown pin receiving block in order to lock the upper receiver to the lower receiver. In order to allow easy entry and removal of the takedown pin, in embodiments of the invention the takedown pin openings in the lower receiver may have a diameterwhich is largerthan the diameterof the takedown pin, while the diameter of the bore in the takedown pin receiving block is substantially the same as the diameter of the takedown pin in order to provide sufficient friction to retain the takedown pin during normal use. The difference in diameter between the takedown pin and the takedown pin openings in the lower receiver allows a similar amount of movement between upper and lower receivers. This movement can be eliminated by pulling the takedown pin receiving block so that it forces the takedown pin into contact with the walls of the takedown pin opening.

[0010] In one embodiment, the adjustable length receiver tensioning assembly selectively imparts a downward and / or rearward and / or lateral force onto the upper receiver towards the lower receiver, thereby forcing the takedown pin into contact with the walls of the takedown pin openings. This force can be adjusted to eliminate any gap or play between two (or more) “receivers” that together make up a firearm. It works by pulling or pushing one receiver towards or into the other by the use of a receiver tensioning arrangement that can access and contact an accessible (called “external” in the following) forward facing or rearward facing surface on one of the receivers, preferably using an angled plane, and push or pull the forward or rearward facing surface in the direction of a rearward facing surface, respectively forward facing surface on another receiver. The receiver tensioning arrangement can be attached to the receiver with a fastener, a specially cut track, a live hinge or a clip. This receiver tensioning arrangement ensures that neither receiver can rotate freely around any other attachment point that might be used to combine the receivers, and that they are pulled together virtually making them behave as one. The method of locking the receivers together can be done with a cam, a screw or ratcheting system to ensure the tension between the parts stays solid throughout use. One or more of the external surfaces can be provided with an angled plane which the receiver tensioning arrangement is in contact with. Angled planes can be made differently whether forward or rearward and / or downward or lateral motion of the upper receiver towards the lower receiver is preferred. This solution reduces any gap between the upper and lower receivers, thereby reducing the of intrusion of dirt, dust, grime or debris, thus lessening the need of required cleaning of the internal parts of the firearm.

[0011] Preferably the receiver tensioning arrangement is arranged towards the rear of a lower receiver and applies force between a rearward facing external surface of the lower receiver and a forward facing external surface of the upper receiver in order to pull or push the upper receiver downwards and / or rearwards and / or laterally onto the lower receiver.

[0012] This summary is provided merely to introduce certain concepts and not to identify key or essential features of the claimed subject matter.

[0013] BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Presently preferred embodiments are shown in the drawings. It should be appreciated, however, that the invention is not limited to the precise arrangements and instrumentalities shown.Figure 1 shows a schematic side view of a lower receiver and upper receiver assembly according to the invention for an AR-15 firearm in the closed position.

[0015] Figure 2 shows a schematic rearview of a lower receiver and upper receiver assembly of figure 1. Figure 3 shows a schematic side view of the lower receiver and upper receiver assembly of figure 1 in the open position.

[0016] Figure 4 shows a schematic view of the rears of the lower receiver and upper receiver from figure 3.

[0017] Figure 5 shows a schematic perspective view from the upper left rearview of a lower receiver and upper receiver assembly according to the invention for an AR-15 firearm.

[0018] Figure 6 shows a schematic lateral sectional view of a lower receiver and upper receiver according to the invention for an AR-15 firearm.

[0019] Figure 7 shows an enlarged schematic lateral view of an example of a tensioning arrangement according to the invention.

[0020] Figure 8 shows an enlarged schematic perspective lateral view of an example of another tensioning arrangement according to the invention.

[0021] Figure 9 shows another enlarged schematic lateral view of the tensioning arrangement according to the invention shown in figure 8.

[0022] Figure 10 shows schematically a view from the side of an embodiment of a tensioning arrangement with the upper and lower receiver, before they are joined together.

[0023] DETAILED DESCRIPTION OF THE INVENTION

[0024] While the specification concludes with claims defining the features of the invention that are regarded as novel, it is believed that the invention will be better understood from a consideration of the description in conjunction with the drawings. As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention which can be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the inventive arrangements in virtually any appropriately detailed structure. Further, the terms and phrases used herein are not intended to be limiting but rather to provide an understandable description of the invention.

[0025] Definitions

[0026] As described herein, the term “removably secured,” and derivatives thereof shall be used to describe a situation wherein two or more objects are joined together in a non-permanent manner so as to allow the same objects to be repeatedly joined and separated.

[0027] As described throughout this document, the term “complementary shape,” and “complementary dimension,” shall be used to describe a shape and size of a component that is identical to, or substantially identical to the shape and size of another identified component within a tolerance such as, for example, manufacturing tolerances, measurement tolerances or the like.One embodiment of a firearm receiver with an adjustable length receiver tensioning assembly in the form of a receiver tensioning assembly is described below with reference to the drawings. In each of the drawings, identical reference numerals are used for like elements of the invention or elements of like function. For the sake of clarity, only those reference numerals are shown in the individual figures which are necessary for the description of the respective figure. For purposes of this description, the terms “upper,” “bottom,” “right,” “left,” “front,” “rear” “vertical,” “horizontal,” and derivatives thereof shall relate to the viewpoint of a shooter during the normal use of a firearm wherein the barrel is facing forward and is in front of the trigger and stock, the trigger is vertically under the barrel and the barrel is substantially horizontal. An “external” surface is a surface which belongs to or forms the outside surface of an element. The wall of a bore in an element for receiving a pivot or takedown pin is not considered to be an external surface for the purposes of this application but is an internal surface.

[0028] Figure 1 shows a schematic side view of a firearm receiver assembly 1 comprising a lower receiver 2 and an upper receivers according to the invention for an AR-15 firearm. Figure 2 shows a schematic rearview of the firearm receiver assembly 1.

[0029] One embodiment of the firearm receiver assembly with an adjustable length receiver tensioning assembly can include a lower receiver 2 having an upper receiver 3 positioned therein.

[0030] FIGS. 3 and 4 illustrate the firearm receiver assembly of figures 1 and 2 in the open position. In the embodiment shown, the lower receiver has a lower receiver body 20 which can be constructed for use as a lower receiver of an AR-15 firearm and can include functionality for engaging any number of associated rifle components such as, for example, a handgrip, shoulder stock, trigger assembly, and an upper receiver 3. Each of these components, and their operability with a lower receiver, are well known in the art.

[0031] Although described and illustrated with regard to an AR-15 rifle, those of skill in the art will recognize that the same principals can be applied to any type of firearm having an upper receiver and lower receiver components without undue experimentation. Therefore, the inventive concepts are not to be construed as limiting to only an AR-15 rifle. Furthermore, while the invention is described with an example in which the adjustable length receiver tensioning assembly is in the form of an adjustable length receiver tensioning assembly acting at the rear of the receiver assembly, it is applicable to any suitable place on a receiver assembly.

[0032] In one embodiment of a firearm lower receiver 2 according to the present invention, the lower receiver comprises a lower receiver body 20 having a front end 21 a, a back end 21 b, a top end 21 d, a bottom end 21c, a pairof side walls 21 e, 21 f, and a backend block section 24 positioned between the pair of side walls 21 e, 21 f which supports a conventional back end extension 25. Backend extension 25, also known as a buffer tube extension, is in the shape of a ringwith a threaded inner circumference to a buffer tube can be treaded. Lower receiver body 20 has an opposed pairof rear takedown pin apertures 23a, 23b each of which are positioned along one of the pair of side walls and are aligned with each other. Preferably the takedown pin apertures 23a, 23b can include an elongated / oval shape so as to permit slight movement of the below described takedown pin upon engagement of the adjustable length receiver tensioning assembly 50. Pivot pin apertures 22 can be positioned along the front end of the lower receiver body for receiving a pivot pin 4.In this embodiment of the invention there is a through bore 25 that extends from the external rearward facing surface 26b of the back end block section 24 to the external forward facing surface 26a of the backend block section.

[0033] An upper receiver 3 for use with the above described lower receiver and below described adjustable length receiver tensioning assembly 50 includes a front end 31a , a backend 31b , a bottom end 31c , a top end 31 d and a pair of sides 31 e and 31 f. Pivot pin receiving block 33 with a transverse bore 32 projects down from the front end of the upper receiver body for receiving the pivot pin 4 .

[0034] Takedown pin receiving block 36 with a transverse rear takedown pin bore 38 projects down from the lower rear end of the upper receiver body for receiving the takedown pin 40.

[0035] The takedown pin receiving block 36 comprises an external forward facing surface 36a and an external rearward facing surface 36b.

[0036] As shown in figure 5 which is a perspective cross-section through the upper and lower receiver assembly in the closed position, in order to pull the upper receiver 3 towards the lower receiver 2 there is an adjustable length receiver tensioning assembly 50 in the form of an upper receiver engaging front portion 52 which engages with the forward facing surface 36a of takedown pin receiving block 36 of the upper receiver and has a threaded shaft portion 53 which can be brought into threaded engagement via through bore 25 with an appropriately threaded tensioning rod 54 attached to an upper receiver engaging front portion retracting member in the form of a tensioning knob 56 which abuts the rearward facing surface 26b of backend block section 24 of the lower receiver. Rotating the knob 56 to bring the shaft and rod into increased engagement shortens the length of the adjustable length receiver tensioning assembly 50 and pulls the upper and lower receiver towards each other, thereby reducing any play between them. The amount of relative movement between the upper and lower receiver is limited by the amount of movement allowed by the takedown pin and pivot pin. Preferably the pivot pin is a friction fit in the pivot pin receiving block 33 and a loose fit in the pivot pin apertures 22 which can have a larger diameter or width than the pivot pin to allow sufficient relative movement between the pin and pin apertures to eliminate the undesired play between the upper and lower receivers.

[0037] Similarly, the takedown pin is a friction fit in the takedown pin receiving block 36 and a loose fit in the takedown pin apertures 23a, 23b which can have a larger diameter or width than the pivot pin to allow relative movement between the pin and pin apertures.

[0038] Thus, in this example of the invention, as shown in the lateral views of figures 6 and 7, the upper receiver engaging front portion 52 of adjustable length receiver tensioning assembly 50 comprises a front portion 60 which contacts the forward facing surface 36a of takedown pin receiving block 36 of the upper receiver and which can be pulled backwards by a tensioning rod 54 which extends through the through bore 25 that extends from the rearward facing surface 26b of the back end block section 24 to the forward facing surface 26a of the backend block section and which has a tensioning knob 56 that abuts the rearward facing surface 26a of the back end block section. The tensioning rod 54 is threaded into a threaded shaft portion 53 of clamp 52. The front portion of the clamp 52 is positioned during use against a downward and forward inclined protrusion 37 which forms part of the forward facing surface 36a of takedown pin receiving block 36. This means that part of the forward facing surface 36a is at an angle to the vertical and faces both upwards and forwards. Rotation of the tensioning knob 56 adjusts the length of the adjustable length receiver tensioning assembly 50 and the contact between the inclined protrusion and the front portion of the adjustable length receiver tensioning assembly50 imparts a force on the upper receiver which has a rearward component and a downwards component and can be used to pull the upper receiver towards the lower receiver until contact of the pivot pin 4 or takedown pin 40 with the bores and aperture walls that they transverse prevent further relative movement between the upper and lower receivers. A substantially only rearward force on the upper receiver can be achieved by having vertical surfaces on both the upper and lower receiver as contact points for the adjustable length receiver tensioning assembly 50, especially if these are arranged at the level of the centreline of the takedown pin (shown by a dash and dot line in the figures). Greater or small vertical components to the force on the upper receiver can be achieved by adjusting the angle to the vertical of contact points of the adjustable length receiver tensioning assembly 50 to the upper and lower receiver and / or by adjusting the vertical distance z of such contact points from the level of the centreline of the takedown pin.

[0039] In order to reduce or eliminate lateral play, the adjustable length receiver tensioning assembly 50 and / or the contact points for the adjustable length receiver tensioning assembly 50 can be arranged so that a lateral component to the force pulling (or pushing) the upper receiver towards the lower receiver is generated when the tensioning knob 56 is tensioned.

[0040] For example, this lateral force can be achieved by arranging the adjustable length receiver tensioning assembly 50 so that it is offset a distance y to one side of the longitudinal (i.e. fore and aft) centreline of the upper receiver 3 and / or the longitudinal centreline of the lower receiver 2 so that the upper and lower receivers are brought together with a twisting force, or by arranging the contact point for the adjustable length receiver tensioning assembly 50 to one side of the longitudinal centreline of the upper receiver so that the force generated by adjustable length receiver tensioning assembly 50 during use is inclined at an angle to the longitudinal centreline axis, thereby providing a lateral force component.

[0041] A lateral force can also be achieved when the front portion of the clamp 52 is positioned during use against a laterally inclined protrusion 37 which forms part of the forward facing surface 36a of takedown pin receiving block 36 and which will pull the upper receiver 3 and lower receiver 2 together laterally and axially when tension is applied. Preferably this laterally sloping protrusion is also inclined to the vertical for applying a vertical component to the tensioning force. This means that part of the forward facing surface 36a is inclined at an angle to the vertical and slopes both upwards at the angle of vertical inclination and forwards at the angle of lateral inclination. Rotation of the tensioning knob 56 adjusts the length of the adjustable length receiver tensioning assembly 50 and the contact between the inclined protrusion and the front portion of the adjustable length receiver tensioning assembly 50 imparts a force on the upper receiver which has a sideways component, a rearward component and a downwards component and thus reduces play in all three axes. Such reductions of play are achieved by pulling the upper receiver 3 towards the lower receiver 2 until contact of the pivot pin 4 or takedown pin 40 with the bores and aperture walls that they transverse prevent further relative movement between the upper and lower receivers.

[0042] In the example shown in these figures, the upper receiver engaging front portion 52 is a hook which in use extends in front of said pair of rear takedown pin apertures 23a, 23b and which engages with the external forward facing surface 36a of the takedown pin receiving block 36. The forward facing surface 36a of the takedown pin receiving block 36 may be flat or preferably, as shown in the figures, comprises an inclined protrusion 37 which is inclined down towards the front of the lower receiver when assembled with the upper receiver. When the front portion 60 contacts this inclined protrusion 37 of the forward facing surface 36a of takedown pin receivingblock 36 it can impart a downwards and rearward force on the upper receiver towards the lower receiver. Such forces load the pivot pin 4 and load the takedown pin 32 in a manner that reduces play between the upper and lower receivers.

[0043] In an alternative version of the arrangement shown described above, if there is sufficient space below the backend block section 24, then the through bore 25 can be omitted and the adjustable length receiver tensioning assembly 50 be formed as a G-clamp with dimensions adapted to the space available, In such an arrangement the fixed jaw of the G-clamp may be in contact with the forward facing surface 36a of takedown pin block 36. The frame may pass underneath the takedown pin block 36 and the back end block section 24 and the movable jaw may be in contact and pushed against the rearward facing surface 26b of the back end block section 24.

[0044] The inventive concepts are not limited to arrangement where the tension is provided between at least one forward facing surface attached to an upper receiver and at least one rearward facing surface attached to a lower receiver. To this end, figure 8 and 9 shows schematically in perspective an example of a receiver tensioning arrangement 50 according to the present invention in which the tensioning force is applied to the external forward facing surface of a takedown pin receiving block 36 by a clamp which presses onto an external rearward facing surface suspended from a buffer tube support instead of pressing onto the external rearward facing surface of a back end block section.

[0045] In any embodiment of the present invention, it is envisaged that a surface which the clamp of a receiver tensioning arrangement is in contact with is provided with clamp locating means such as one or more, preferably transverse, grooves, depressions or ridges which can assist in locating the receiver tensioning arrangement in a desired position on the surface. Such clamp locating means can also assist in holding a clamp in position while the lower receiver and upper receiver are being assembled into a receiver assembly.

[0046] While the invention has been described with an example in which the upper receiver is pulled back and / or down towards the lower receiver by a tensioning arrangement which acts at the rear of the upper and lower receiver assembly of an AR-15 as any mechanism positioned here is close to the trigger hand and is simple to operate when the firearm is held in the shooting position, it is applicable to any other position on a receiver assembly. For example, in some firearms, for example some bullpup firearms, where there is a grip or handhold or trigger in the front of the receiver then it may be appropriate to position in that region an adjustable length receiver tensioning assembly which acts on external rearward facing surface on one of the receivers and on the external forward facing surface of the other receiver and which can be operated by the closest hand. Such an arrangement may provide a tensioning force which is vertical and / or forwards or backwards and / or lateral. Adjustable length receiver tensioning assemblies which pull or push an upper receiver forwards or backwards and / or upwards or downwards or sideways to the left or to the right with respect to a lower receiver can also be used with any firearms in which one receiver has at least one external forward facing surface and the other receiver has at least one suitable external rearward facing surface which both can be contacted at the same time by an adjustable length clamping mechanism. Thus, the tensioning arrangement can be arranged in cooperation with forward and rearward facing surfaces to pull the upper and lower receivers together, for example by having a forward facing surface at a forward position on one of the upper or lower receivers and a reward facing surface at a relatively rearward position on the other receiver, with the tensioning arrangement arrangedto pull the forward and rearward facing surfaces towards each other so that they become closer together thereby reducing the play between the upper and lower receivers.

[0047] Alternatively, the tensioning arrangement can be arranged in cooperation with forward and rearward facing surfaces to push the upper and lower receivers away from each other, for example by having a forward facing surface at a rearward position on one of the upper or lower receivers and a rearward facing surface ata relatively forward position on the other receiver, with the tensioning arrangement arranged to push the forward and rearward facing surfaces away from each other so that they become further apart which can also reduce the paly between the upper and lower receivers.

[0048] Figure 10 shows schematically a view from the side of the upper and lower receiver, before they are joined together, of an example of a tensioning arrangement in which there is a forward facing surface 36a at a rearward position on the lower receiver 2 and a rearward facing surface 26a on the upper receivers at a relatively forward position. These surfaces 26a, 36a can be pushed apart by an adjustable tensioning arrangement 50. In this example, this has a threaded rod 62 with at least one threaded movable plate 64 arranged to travel along the rod when the rod is rotated by a tensioning knob 56. Rotating the knob in one direction causes the movable plate 64 to move backwards and contact the forward facing surface, while a forward plate 66 on the threaded rod contacts the rearward facing surface 26a, thereby pushing the forward facing surface 36a and rearward facing surface 26aaway from each other and reducing play between the upper and lower receivers.

[0049] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used herein, the singular forms “a”, “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and / or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof. Likewise, the terms “consisting” shall be used to describe only those components identified. In each instance where a device comprises certain elements, it will inherently consist of each of those identified elements as well.

[0050] The corresponding structures, materials, acts, and equivalents of all means or step plus function elements in the claims below are intended to include any structure, material, or act for performing the function in combination with other claimed elements as specifically claimed. The description of the present invention has been presented for purposes of illustration and description but is not intended to be exhaustive or limited to the invention in the form disclosed. The embodiment was chosen and described in order to best explain the principles of the invention and the practical application, and to enable others of ordinary skill in the art to understand the invention for various embodiments with various modifications as are suited to the particular use contemplated.

Claims

Claims1. A firearm receiver assembly (1) comprising a lower receiver (2) and an upper receiver (3) wherein one of said receivers has at least one external forward facing surface (36a) and the other receiver has at least one external rearward facing surface (26b) characterised by an adjustable length receiver tensioning assembly (50) which is in contact with both the external forward facing surface (36a) and the external rearward facing surface (26b) and is operable to pull said external forward facing surface (36a) and said external rearward facing surface (26b) towards each other or to push said external forward facing surface (36a) and said external rearward facing surface (26b) away from each other .

2. A firearm receiver assembly according to claim 1, further comprising a takedown pin (40), wherein:said lower receiver (2) comprises:a body (20) having a front end (21a), a backend (21 b), a top end (21 d), a bottom end (21c), a pair of side walls (21 e, 21 f) each with a takedown pin aperture (23a, 23b), and a backend block section (24), positioned between said pair of side walls, said back end block section (24) having said at least one external rearward facing surface (26b);andsaid upper receiver (3) comprises a transverse rear takedown pin aperture formed in a takedown pin receiving block (36) comprising said at least one external forward facing surface (36a), characterised in that said adjustable length receiver tensioning assembly (50) is in contact with said at least one external forward facing surface (36a) and said at least one external rearward facing surface (26b) for pulling said back end block section (24) towards said takedown pin receiving block (36) or pushing said back end block section (24) away from said takedown pin receiving block (36).

3. Firearm receiver assembly according to claim 2 wherein said adjustable length receiver tensioning assembly (50) comprising an upper receiver engaging front portion (52) which extends in front of said pair of takedown pin apertures (23a, 23b) and is in contact with said external forward facing surface (36a), and an upper receiver engaging front portion retracting member (56) which is in contact with the external rearward facing surface (26b) and which can be operated to pull said upper receiver engaging front portion (52) towards said upper receiver engaging front portion retracting member (56).

4. Firearm receiver assembly according to any of claim 2 or 3 characterised in that upper receiver engaging front portion (52) has a rearward facing front portion (60) which abuts said external forward facing surface (36a).

5. Firearm receiver assembly according to any of claims 3 to 4 characterised in that said lower receiver comprises a through bore (25) that extends towards the front end (21 a) from the back end (21 b) of the body through the block section (24); andsaid upper receiver engaging front portion retracting member (56) comprises a tensioning rod (54) which extends through said through bore (25) and which is adapted to engage with upper receiver engaging front portion (52);9and said upper receiver engaging front portion retracting member (56) is adapted move said tensioning rod (54) towards or away from said external forward facing surface (36a).

6. Firearm receiver assembly according to claim 5, wherein said through bore (25) is horizontal.

7. Firearm receiver assembly according to claim 5 or claim 6, wherein said through bore (25) is horizontally and / or vertically inclined to a longitudinal central axis of the lower receiver and / or vertically offset a distance y and / or laterally offset a distance z from the axial centreline of the lower receiver.

8. Firearm receiver assembly according to any of the previous claims wherein said upper receiver engaging front portion retracting member (56) and said upper receiver engaging front portion (52) are in threaded engagement.

9. Firearm receiver assembly according to any of the previous claims wherein said upper receiver engaging front portion retracting member (56) has a rotatable threaded tensioning rod (54) which extends through said through bore (25) and engages a threaded shaft portion (53) of said upper receiver engaging front portion (52).

10. Firearm receiver assembly according to any of the previous claims, wherein said adjustable length receiver tensioning assembly (50) is arranged to impart longitudinal and / or vertical and / or lateral forces between the upper receiver (3) and the lower receiver (2).

11. Firearm receiverassemblyaccordingto any of claims 1 to 10 wherein said external forward facing surface (36a) comprises an inclined portion (37).

12. Firearm receiver assembly according to any of claims 1 to 11 wherein said external forward facing surface (36a) comprises an inclined portion (37) which is inclined vertically and / or laterally.

13. A firearm lower receiver (2), comprising:a body (20) having a front end (21a), a backend (21 b), a top end (21c), a bottom end (21 d), a pair of side walls (21e, 21f), and a backend block section (24) positioned between the pairof side walls;an opposed pair of rear takedown pin apertures (23a, 23b) each of which are positioned along one of the pair of side walls;a through bore (25) that extends towards the front end (21a) from the back end (21 b) of the body through the block section (24); andan adjustable length receiver tensioning assembly (50) comprising an upper receiver engaging hook (52) which extends in front of said pair of rear takedown pin apertures (23a, 23b) and an upper receiver engaging front portion retracting member (56) which extends through said through bore (25) and which is adapted to move said upper receiver engaging front portion (52) towards or away from said rear takedown pin apertures (23a, 23b).

Images