Magazine extension

1. A ammunition magazine extension assembly for an elongated magazine tube defining an internal passage, having an upper end with feed lips defining an ammunition exit aperture, and a lower end having a floor plate attachment facility, the assembly comprising:

an extension body having a floor panel, a right side wall, and an opposed left side wall, and a front wall;

the right and left side walls each including linear engagement facilities each configured to engage the floor plate attachment facility;

the extension body defining a chamber between the right and left side walls and rear of the front wall, and open in an upward direction;

the linear engagement facilities being operable to constrain movement of the extension body between an attached condition in which the chamber is registered with the internal passage, and a detached condition;

a door slidably and removably connected to the extension body and having an upper door edge;

the door movable between an attached condition in which the door spans between rear or front portions of the right and left side walls, and a detached condition;

the upper edge of the door when in the attached condition abutting a lower portion of the elongated magazine tube to prevent forward movement of the extension body from the attached condition, and enabling movement of the extension body to the detached condition when the door is removed; and

a lock element on the extension body having a locked condition and an unlocked condition and operable to engage the door to prevent removal of the door when in the locked condition and to enable removal of the door when in the unlocked condition.

2. The ammunition magazine extension assembly of claim 1 wherein the floor plate attachment facility includes opposed flanges and the linear engagement facilities are grooves configured to closely and slidably receive the opposed flanges.

3. The ammunition magazine extension assembly of claim 1 wherein the door is slidably connected to the extension body by a linear attachment element.

4. The ammunition magazine extension assembly of claim 1 wherein the door is slidably connected to the extension body by a flange and groove facility.

5. The ammunition magazine extension assembly of claim 1 wherein the linear engagement facilities define a first axis of motion, and the door defines a second axis of motion angularly offset from the first axis of motion.

6. The ammunition magazine extension assembly of claim 1 wherein the lock element is rotatably connected to the extension body.

7. The ammunition magazine extension assembly of claim 6 wherein the lock element rotates on a vertical axis.

8. The ammunition magazine extension assembly of claim 1 wherein the door defines a ledge, and the lock has a movable element configured to engage the ledge when in the locked condition.

9. The ammunition magazine extension assembly of claim 1 wherein the lock element is a planar body with a circular periphery.

10. An ammunition magazine comprising:

an elongated magazine tube defining an internal passage, having an upper end with feed lips defining an ammunition exit aperture, and a lower end having a floor plate attachment facility,

an extension body having a floor panel, a right side wall, and an opposed left side wall, and a front wall;

the right and left side walls each including linear engagement facilities each configured to engage the floor plate attachment facility;

the extension body defining a chamber between the right and left side walls and rear of the front wall, and open in an upward direction;

the linear engagement facilities being operable to constrain movement of the extension body between an attached condition in which the chamber is registered with the passage, and a detached condition;

a door slidably and removably connected to the extension body and having an upper door edge;

the door movable between an attached condition in which the door spans between rear portions of the right and left side walls, and a detached condition;

the upper edge of the door when in the attached condition abutting a lower portion of the magazine tube to prevent forward movement of the extension body from the attached condition, and enabling movement of the extension body to the detached condition when the door is removed, and

a lock element on the extension body having a locked condition and an unlocked condition and operable to engage the door to prevent removal of the door when in the locked condition and to enable removal of the door when in an unlocked condition.

11. The ammunition magazine of claim 10 wherein the floor plate attachment facility includes opposed flanges and the engagement facilities are grooves configured to closely and slidably receive the opposed flanges.

12. The ammunition magazine of claim 10 wherein the door is slidably connected to the extension body by a linear attachment element.

13. The ammunition magazine of claim 10 wherein the door is slidably connected to the extension body by a flange and groove facility.

14. The ammunition magazine of claim 10 wherein the linear engagement facilities define a first axis of motion, and the door defines a second axis of motion angularly offset from the first axis.

15. The ammunition magazine of claim 10 wherein the lock element is rotatably connected to the extension body.

16. The ammunition magazine of claim 15 wherein the lock element rotates on a vertical axis.

17. The ammunition magazine of claim 10 wherein the door defines a ledge, and the lock has a movable element configured to engage the ledge when in the locked condition.

18. The ammunition magazine of claim 10 wherein the lock element is a planar body with a circular periphery.