Bolt carrier assembly for a firearm

Abstract

A bolt carrier assembly for improving primary extraction in a firearm, wherein the bolt carrier assembly includes a bolt carrier and a bolt carried by the bolt carrier, wherein the bolt carrier assembly includes a first camming arrangement for rotating the bolt relative to the bolt carrier for locking the bolt against the locking piece, and a second camming arrangement for forcing longitudinal movement of the bolt relative to the locking piece.

Description

[0001] BOLT CARRIER ASSEMBLY FOR A FIREARM

[0002] FIELD OF THE INVENTION

[0003] The present invention relates to a bolt carrier assembly for a firearm. More specifically, the present invention relates to a bolt carrier assembly for improving primary extraction of a firearm.

[0004] BACKGROUND TO THE INVENTION

[0005] It is known that upon firing of a firearm, a case may deform or expand to the point where it may be difficult to remove the case from the chamber. The initial extraction of a case from a chamber after firing is referred to as primary extraction. Although attempts have been made to use mechanical advantage to facilitate primary extraction, the applicant has identified that it would be advantageous if there was a more compact and / or more efficient arrangement for primary extraction. In particular, the applicant has identified that with particular forms of firearms, such as firearms having smaller bolt rotations, it would be beneficial for there to be provided a mechanism which facilitates primary extraction.

[0006] Examples of the present invention seek to provide a bolt carrier assembly, and / or a firearm having a bolt carrier assembly, which alleviates or at least ameliorates one or more disadvantages of existing firearms, or at least provides a useful alternative.

[0007] SUMMARY OF THE INVENTION

[0008] In accordance with one aspect of the present invention, there is provided a bolt carrier assembly for improving primary extraction in a firearm, wherein the bolt carrier assembly includes a bolt carrier and a bolt carried by the bolt carrier, wherein the bolt carrier assembly includes a first camming arrangement for rotating the bolt relative to the bolt carrier for locking the bolt against the locking piece, and a second camming arrangement for forcing longitudinal movement of the bolt relative to the locking piece. Preferably, the first camming arrangement has a camming pin on the bolt which rides against a camming surface on the bolt carrier.

[0009] In a preferred form, the second camming arrangement has a camming lug on the bolt which rides against a camming surface on the locking piece. More preferably, the camming surface on the locking piece is in the form of a camming face.

[0010] Preferably, the bolt carrier includes a receptacle for receiving the camming lug. More preferably, the receptacle and the camming lug are sized such that, when the camming lug is received in the receptacle it protrudes proud of a forward surface of the carrier to facilitate camming abutment against the camming face.

[0011] It is preferred that, in response to forward movement of the bolt carrier, said first camming arrangement rotates the bolt relative to the bolt carrier into a locked configuration in which the bolt is locked against the locking piece to limit rearward movement of the bolt relative to the locking piece. More preferably, the bolt includes a plurality of radial lugs, the locking piece includes a plurality of radial passages, and the locked configuration is achieved by rotating the bolt relative to the locking piece once the radial lugs are passed through the radial passages.

[0012] Preferably, the first camming arrangement has a radial camming pin extending radially from the bolt which rides against a curved camming surface on the bolt carrier.

[0013] In a preferred example, the camming face is angled out of a plane transverse to a longitudinal axis of the firearm. More preferably, the camming face is helical such that the bolt is forced rearward relative to the locking piece due to operation of the second camming arrangement as the bolt carrier is rotated after firing of the firearm.

[0014] Preferably, the bolt carrier assembly forms part of a firearm having a two-part receiver. More preferably, the bolt carrier assembly forms part of a firearm in the form of a modular rifle. Even more preferably, the firearm is in the form of a modern sporting rifle. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Preferred embodiments of the invention will be described, by way of a non-limiting example only, with reference to the accompanying drawings in which:

[0016] Figure 1 is a perspective view of a front end of a bolt within a bolt carrier in accordance with an example of the present invention;

[0017] Figure 2 shows a perspective view of the bolt, highlighting radial locking lugs;

[0018] Figure 3 shows a perspective view of a bolt locking piece;

[0019] Figure 4 shows an end view of the bolt locking piece;

[0020] Figure 5 shows a perspective view of the bolt carrier assembly in a closed position;

[0021] Figure 6 shows a perspective view of the bolt carrier assembly together with the locking piece, shown in the locked position;

[0022] Figure 7 shows a sectional view of the bolt carrier assembly together with the locking piece, shown in the locked position; and

[0023] Figure 8 shows detail of a camming lug of the bolt engaging with a camming face of the locking piece.

[0024] DETAILED DESCRIPTION

[0025] With reference to Figures 1 to 8 of the drawings, there is depicted a bolt carrier assembly 10 for improving primary extraction in a firearm. The bolt carrier assembly 10 includes a bolt carrier 12 and a bolt 14 carried by the bolt carrier 12. The bolt carrier assembly 10 includes a first camming arrangement 16 for rotating the bolt 14 relative to the bolt carrier 12 for locking the bolt 14 against the locking piece 18, and a second camming arrangement 20 for forcing longitudinal movement of the bolt 14 relative to the locking piece 18.

[0026] In the example shown in the drawings, the first camming arrangement 16 has a camming pin 22 on the bolt 14 which rides against a camming surface 24 on the bolt carrier 12. Figure 1 shows the first camming arrangement 16 in an open position and Figure 5 shows the first camming arrangement 16 in a closed position.

[0027] The second camming arrangement 20 may have a camming lug 26 on the bolt 14 which rides against a camming surface 28 on the locking piece 18. The camming surface on the locking piece may be in the form of a camming face 28. Detail of the second camming arrangement 20 is shown in Figure 8.

[0028] As shown in Figure 5 and Figure 6, the bolt carrier 12 includes a receptacle 30 for receiving the camming lug 26. More preferably, the receptacle 30 and the camming lug 26 are sized such that, when the camming lug 26 is received in the receptacle 30 it protrudes proud of a forward surface 32 of the carrier 12 to facilitate camming abutment against the camming face 28 (see Figure 8).

[0029] Accordingly, in response to forward movement of the bolt carrier 12, the first camming arrangement 16 rotates the bolt 14 relative to the bolt carrier 12 into a locked configuration (see Figure 6 and Figure 7) in which the bolt 14 is locked against the locking piece 18 to limit rearward movement of the bolt 14 relative to the locking piece 18. More preferably, the bolt 14 includes a plurality of radial lugs 34 (see parts highlighted in Figure 2), the locking piece 18 includes a plurality of radial passages 36 (see Figures 3 and 4), and the locked configuration is achieved by rotating the bolt 14 relative to the locking piece 18 once the radial lugs 34 are passed through the radial passages 36.

[0030] As shown most clearly in Figure 1 and Figure 5, the first camming arrangement 16 has a radial camming pin 22 extending radially from the bolt 14 which rides against a curved camming surface 24 forming part of a curved slot 38 on the bolt carrier 12.

[0031] With reference to Figure 3 and Figure 8, the camming face 28 is angled out of a plane transverse to a longitudinal axis of the firearm. In particular, the camming face 28 may be helical such that the bolt 14 is forced rearward relative to the locking piece 18 due to operation of the second camming arrangement 20 as the bolt carrier 12 is rotated after firing of the firearm. Specifically, the locking piece inward radial locking lugs 40 and mating bolt lugs 34 faces are helical. As the bolt 14 is rotated, it essentially unscrews and the bolt cam lug 26 is controlled by the locking piece 18 camming surface 28.

[0032] The bolt carrier assembly 10 may form part of a firearm having a two-part receiver. Pins, screws, bolts and / or other fasteners may be used for joining the upper and lower receivers. More preferably, the bolt carrier assembly 10 forms part of a firearm in the form of a modular rifle. Even more preferably, the firearm may be in the form of a modem sporting rifle.

[0033] Example

[0034] As will be appreciated from the above, an example of the present invention provides a bolt 14 for a rifle which improves primary extraction. The bolt 14 may be part of an assembly. With reference to Figure 1, the assembly 10 has a bolt 14 (see light grey part), a cam pin 22 (green), a bolt carrier 12 (dark grey) with a cam path along the curved slot 38 (red). The bolt 14 has two or more radial lugs 34 that are used to lock the bolt 14 into a mating part locking piece 18 (the radial lugs 34 are shown in blue colour in Figure 2).

[0035] The bolt 14 rotates to lock and unlock. The bolt 14 is controlled by the cam path (red) and the cam pin 22 (green) in the bolt carrier 12. The purple recess or receptacle 30 shown in Figure 1 in the bolt carrier 12 is for the camming lug 26 in the locked position - this allows for maximum bolt travel in the axial direction.

[0036] This additional lug 26 (the yellow lug in Figure 1) is used to aid primary extraction and this lug 26 is not used to lock the bolt 14. This lug 26 cams against a mating part (locking piece 18) to aid primary extraction. Both the bolt lugs 26 and 34, the mating part locking lugs 40 and the camming surface 28 are all cut in a helix (3 mm pitch). This is essentially an interrupted thread. During the unlocking phase (rotation of 22.5° from locked to unlocked) the camming lug 26 engages with the camming surface 28 (see Figure 8) in the mating part (locking piece 18) to drive the bolt rearwards.

[0037] With reference to Figure 2 showing detail of the bolt 14, the locking lugs 34 are blue and the primary extraction camming lug 26 is yellow.

[0038] As depicted in Figure 3 and Figure 4, the bolt lock or locking piece 18 shows a yellow face 42 which is where the camming lug 26 engages to drive the bolt 14 rearwards. This is a helix cut. In Figure 4, inward radial locking lugs 40 of the locking piece 18 are shown in blue and define the radial passages 36 therebetween through which the radial lugs 34 of the bolt 14 may pass before relative rotation for locking of the outward radial lugs 34 of the bolt 14 against the inward radial locking lugs 40 of the locking piece 18.

[0039] Figure 5 shows the bolt assembly in the closed position in which the camming pin 22 resides at a rear of the camming curved slot 38, and in which the camming lug 26 is received in the receptacle 30 formed in a forward face 32 of the bolt carrier 12. Figure 6 shows the bolt carrier assembly 10 and the locking piece 18, shown in the locked position, and Figure 7 shows a sectional view of the locked position. Figure 8 shows detail of the camming lug 26 of the bolt 14 engaging with the camming face 28 of the locking piece 18.

[0040] In one example, there is provided a firearm with upper and lower receivers, joined by pins or screws, bolts or other fasteners. In particular, one example may use screws rather than pins for the disassembly process.

[0041] While various embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not by way of limitation. It will be apparent to a person skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Thus, the present invention should not be limited by any of the above described exemplary embodiments.

[0042] The reference in this specification to any prior publication (or information derived from it), or to any matter which is known, is not, and should not be taken as an acknowledgment or admission or any form of suggestion that that prior publication (or information derived from it) or known matter forms part of the common general knowledge in the field of endeavour to which this specification relates. List of features in drawings

[0043] 10 Bolt carrier assembly

[0044] 12 Bolt carrier

[0045] 14 Bolt carried by the bolt carrier

[0046] 16 First camming arrangement

[0047] 18 Locking piece

[0048] 20 Second camming arrangement

[0049] 22 Camming pin

[0050] 24 Camming surface

[0051] 26 Camming lug

[0052] 28 Camming face

[0053] 30 Receptacle

[0054] 32 Forward surface of the carrier

[0055] 34 Radial locking lugs

[0056] 36 Radial passages

[0057] 38 Curved slot

[0058] 40 Mating part inward radial locking lugs

[0059] 42 Yellow face

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A bolt carrier assembly for improving primary extraction in a firearm, wherein the bolt carrier assembly includes a bolt carrier and a bolt carried by the bolt carrier, wherein the bolt carrier assembly includes a first camming arrangement for rotating the bolt relative to the bolt carrier for locking the bolt against a locking piece, and a second camming arrangement for forcing longitudinal movement of the bolt relative to the locking piece.

2. A bolt carrier assembly as claimed in claim 1, wherein the first camming arrangement has a camming pin on the bolt which rides against a camming surface on the bolt carrier.

3. A bolt carrier assembly as claimed in claim 1 or claim 2, wherein the second camming arrangement has a camming lug on the bolt which rides against a camming surface on the locking piece.

4. A bolt carrier assembly as claimed in claim 3, wherein the camming surface on the locking piece is in the form of a camming face.

5. A bolt carrier assembly as claimed in claim 3 or claim 4, wherein the bolt carrier includes a receptacle for receiving the camming lug.

6. A bolt carrier assembly as claimed in claim 5, wherein the receptacle and the camming lug are sized such that, when the camming lug is received in the receptacle it protrudes proud of a forward surface of the carrier to facilitate camming abutment against the camming face.

7. A bolt carrier assembly as claimed in any one of claims 1 to 6, wherein said first camming arrangement rotates the bolt relative to the bolt carrier into a locked configuration in which the bolt is locked against the locking piece to limit rearward movement of the bolt relative to the locking piece.

8. A bolt carrier assembly as claimed in claim 7, wherein the bolt includes a plurality of radial lugs, the locking piece includes a plurality of radial passages, and the locked configuration is achieved by rotating the bolt relative to the locking piece once the radial lugs are passed through the radial passages.

9. A bolt carrier assembly as claimed in any one of claims 1 to 8, wherein the first camming arrangement has a radial camming pin extending radially from the bolt which rides against a curved camming surface on the bolt carrier.

10. A bolt carrier assembly as claimed in claim 4, or any one of claims 5 to 9 when dependent on claim 4, wherein the camming face is angled out of a plane transverse to a longitudinal axis of the firearm.

11. A bolt carrier assembly as claimed in claim 10, wherein the camming face is helical such that the bolt is forced rearward relative to the locking piece due to operation of the second camming arrangement as the bolt carrier is rotated after firing of the firearm.

12. A bolt carrier assembly as claimed in any one of claims 1 to 11, wherein the bolt carrier assembly forms part of a firearm having a two-part receiver.

13. A bolt carrier assembly as claimed in claim 12, wherein the bolt carrier assembly forms part of a firearm in the form of a modular rifle.

14. A bolt carrier assembly as claimed in claim 13, wherein the firearm is in the form of a modern sporting rifle.

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