Magazine extension for a firearm

A method for increasing the capacity of an ammunition magazine which includes a magazine tube, a follower, a spring, and a lock plate, the method comprising:

• providing the ammunition magazine;
• providing a magazine extension comprising:
• an extension body having an open upper end configured to be slidably coupled with an open bottom end of the magazine tube,
• a passage extending through a rear wall of the extension body,
• a retaining member removably receivable in the passage to releasably secure the extension body to the magazine tube, and
• a base plate configured to be slidably coupled with an open lower end of the extension body to releasably secure the retaining member in the passage;
• coupling the open bottom end of the magazine tube with the open upper end of the extension body;
• inserting the retaining member into the passage of the extension body;
• inserting the follower, spring, and lock plate into the magazine tube through the open lower end of the extension body;
• and
• coupling the base plate with the open lower end of the extension body.

An ammunition magazine for a firearm, comprising:

• a magazine tube defining a first interior space;
• an extension body defining a second interior space, the extension body having an open upper end with which a bottom end of the magazine tube is slidably coupled;
• a passage defined through a rear wall of the extension body, the passage having an upper end which is spaced rearwardly from the second interior space by a distance equal to or greater than a thickness of a rear wall of the magazine tube;
• a retaining member received in the passage;
• a base plate slidably coupled with a lower end of the extension body such that the base plate obstructs the lower end of the passage;
• a hole defined through the base plate;
• a follower received in the first interior space;
• a lock plate received in the second interior space, the lock plate having a downwardly extending protrusion formed on a lower surface thereof;
• and
• a spring received in the first and second interior spaces between the follower and an upper surface of the lock plate, the spring biasing the protrusion of the lock plate into the hole of the base plate;
• wherein a tip portion of the retaining member protrudes out of the upper end of the passage and overlaps the rear wall of the magazine tube to limit sliding movement of the magazine tube relative to the extension body and releasably secure the extension body to the magazine tube.

A magazine extension, comprising:

• an extension body defining an interior space and an open upper end configured to be slidably coupled with an open bottom end of a magazine tube for an ammunition magazine;
• a passage defined through a rear wall of the extension body;
• a retaining member configured to be removably received in the passage, wherein a tip portion of the retaining member protrudes out of an upper end of the passage and overlaps a rear wall of the magazine tube to limit sliding movement of the magazine tube relative to the extension body and releasably secure the extension body to the magazine tube when the magazine tube is coupled with the extension body and the retaining member is received in the passage;
• a base plate configured to be slidably coupled with an open lower end of the extension body, wherein the base plate obstructs a lower end of the passage and prevents the retaining member from exiting the lower end of the passage when the retaining member is received in the passage and the base plate is coupled with the extension body;
• and
• a hole extending through the baseplate;
• wherein a protrusion extending downwardly from a lock plate for the ammunition magazine is receivable in the hole of the base plate to secure the base plate to the extension body.