Modular firearm
View Patent ↗A firearm having a lower receiver is provided. The receiver is adapted to couple with a plurality of upper receivers having different calibers. The lower receiver comprises a receiver extension having an opening therein. A spring is disposed within the opening. A buffer member is provided having a first portion having an end. The buffer member is coupled to the spring within the opening, wherein the buffer member is movable between a first position where the end is within the opening and a second position wherein the end external to the opening.
1. A firearm comprising:
a lower receiver having an extension portion with an opening, the lower receiver being configured to selectively couple with a first upper receiver having a first barrel and a first bolt carrier assembly, the first upper receiver sized to receive a first bullet having a first caliber and a second upper receiver, having a second barrel and a second bolt carrier assembly, the second upper receiver sized to receive a second bullet having a second caliber, the second caliber being smaller than the first caliber; and,
a buffer assembly common to both the first upper receiver and the second upper receiver and disposed at least partially within the opening, the buffer assembly including a biasing member and a buffer member, the buffer member being movable in a range defined by a first position wherein the buffer assembly is compressed by recoil forces and gasses generated by firing of either the first bullet or the second bullet from the firearm, and a second position wherein a first portion of the buffer member extends past the opening towards a forward end of the firearm or a third position wherein a face of the first portion remains flush with the opening, wherein the buffer member is movable between the first position and the second position when the first upper receiver is coupled to the lower receiver and wherein the buffer member is movable between the first position and the third position when the second upper receiver is coupled to the lower receiver.
2. The firearm of claim 1 wherein:
the biasing member has an outer diameter sized to fit with-in the opening and an inner diameter; and,
wherein the first portion of the buffer member has an outer diameter sized to fit within the opening and a second portion of the buffer member has an outer diameter sized to fit within the inner diameter of the biasing member.
3. The firearm of claim 2 wherein the outer diameter of the first portion is sized to keep the buffer assembly substantially axially aligned with the opening.
4. The firearm of claim 2 wherein:
the first portion of the buffer member includes a portion that remains within the opening when the first portion extends past the opening.
5. The firearm of claim 4 wherein the first portion remains flush with the opening when the buffer member is in the third position.
6. A firearm comprising;
a lower receiver having an extension portion with an opening having a first end and a second end, the lower receiver being configured to selectively couple with a plurality of upper receivers, wherein each of the plurality of upper receivers has a distinct barrel and bolt carrier assembly configured to receiver a bullet having a different caliber;
a biasing member disposed within the opening, the biasing member having a first end and a second end, the first end of the biasing member being in contact with the second end of the opening; and,
a buffer member common to each of the plurality of upper receivers and having a first portion operably coupled to the second end of the biasing member, the buffer member also includes a second portion having a diameter sized to axially align the buffer member within the opening, wherein the buffer member is movable in a range defined by a first position wherein the buffer assembly is compressed towards the first end of the opening by recoil forces and gasses generated by firing of the bullet from the firearm and a first extended position wherein a face of the second portion extends past the opening or a second extended position wherein the face is flush with the opening, and wherein the first extended position is associated with at least one of the plurality of upper receivers and wherein the second extended position is associated with at least one other one of the plurality of upper receivers, wherein the second portion is at least partially disposed within the opening in the first extended position and the second extended position.
7. The firearm of claim 6 wherein the first portion is sized to fit within an inner diameter of the biasing member.
8. The firearm of claim 6 wherein the plurality of upper receivers includes a first upper receiver and a second upper receiver, the first upper receiver being sized to receive a first bullet having a first caliber, and the second upper receiver being sized to receive a second bullet having a second caliber, the second caliber being larger than the first caliber.
9. The firearm of claim 8 , wherein
the buffer member is movable between the first position and the second extended position when the first upper receiver is coupled to the lower receiver; and,
the buffer member is movable between the first position and the first extended position when the second upper receiver is coupled to the lower receiver.
10. The firearm of claim 8 wherein the first upper receiver is configured to receive a NATO 5.56 mm bullet.
11. The firearm of claim 10 wherein the second upper receiver is configured to receive a NATO 7.62 mm bullet.
12. A method of operating a firearm comprising:
coupling a first upper receiver to a lower receiver, the lower receiver having an extension portion having an opening, the first upper receiver having a first barrel and a first bolt carrier assembly;
moving a buffer member between a first position and a second position during operation of the firearm when the first upper receiver is secured to the lower receiver, the buffer member extending at least partially past the opening when the buffer member is in the second position and the first upper receiver is secured to the lower receiver;
removing the first upper receiver from the lower receiver;
coupling a second upper receiver to the lower receiver, the second upper receiver having a second barrel and a second bolt carrier assembly; and,
moving the buffer member between the first position and a third position during operation of the firearm when the second upper receiver is secured to the lower receiver, wherein a face of the buffer member is flush with the opening when the buffer member is in the third position and the second upper receiver is secured to the lower receiver, and wherein the buffer member is common to both the first upper receiver and the second upper receiver.
13. The method of claim 12 , wherein the first upper receiver is configured to receive a NATO 7.62 mm bullet and wherein the second upper receiver is configured to receive a NATO 5.56 mm bullet.
14. The method of claim 13 , wherein the first bolt carrier is configured to receive a NATO 7.62 mm bullet and wherein the second bolt carrier is configured to receive a NATO 5.56 mm bullet.
15. The method of claim 14 , wherein a portion of the buffer member remains within the opening when the buffer member is in the second position.
16. The method of claim 15 , wherein a portion of the buffer member is received within a biasing member located in the extension portion.