Drum magazine

• US 4,487,103 A
• Filed: 06/24/1982
• Issued: 12/11/1984
• Est. Priority Date: 06/24/1982
• Status: Expired due to Term

• Current Assignee: Maxwell G. Atchisson
• Original Assignee: Maxwell G. Atchisson
• Inventors: Atchisson, Maxwell G.
• Primary Examiner(s): Schafer, Richard E.
• Assistant Examiner(s): Cornwell, David K.
• Application Number:
  US06/391,665
• Time in Patent Office: 901 Days
• Field of Search: 89/33 D, 89/33 R, 89/33 SF, 42/50, 42/19
• US Class Current: 89/33.02
• CPC Class Codes: F41A 9/73 Drum magazines

Abstract

A drum magazine particularly intended for feeding shotgun shells to a firearm such as an autoloading assault shotgun. The drum magazine includes a cartridge-carrying rotor having a pair of sprockets, and powered by a torsion spring disposed on a central post within the drum. A last-round cartridge follower, removably carried by the rotor, can move either to a radially-extended position to feed the last round from the drum, or to a position of reduced effective radius to accommodate the first round in the fully-loaded drum. The drum magazine is adaptable to shells of different lengths.

Claims

1. A drum magazine for storing and feeding rounds of ammunition to a firearm, comprising:

a body;

a rotor within said body and biased for rotation;

a plurality of discrete round-receiving recesses defined about the periphery of said rotor to engage and carry a corresponding plurality of rounds along a path within said body;

extension means extending from said body for placement in round feeding relation with a firearm, said extension means having a round-feeding opening and means providing a round feeding path between the extension means and said rotor so that the biased rotation of the rotor serially moves each round-receiving recess to the extension means;

follower means carried by said rotor behind the last round-receiving recess to arrive at the extension means, said follower means operatively assuming a radially extended first position to engage the last round and displace that round outwardly from the rotor recess toward said round-feeding opening when the last round-receiving recess is in round feeding relation to the extension means; and

said follower means being movable inwardly to a second position to allow the rotor to be moved past the fully loaded position, thereby providing sufficient room to enable a closed first round of the fully-loaded drum magazine to be displaced in said extension means by the presence of a closed bolt in the firearm when the magazine is placed on the firearm.

2. A drum magazine as in claim 1, further comprising:

feed means cooperating with said rotor means to define said round feeding path between said round-receiving recesses and said extension means;

stationary means located for engagement by said follower means so as to contact the follower means and limit rotation of said rotor means as the last round-feeding recess bears a predetermined relation to said feed mens;

said follower means being movable to said first position to feed the last round along said feed means to said extension means; and

said follower means being displacable to said second position in response to contacting said stationary means as said rotor moves against said bias to the fully-loaded position to place the first round-receiving recess at said feed means, so that the follower means in said second position permits limited further rotation of the rotor means past the fully-loaded position;

whereby said further rotation allows the last-loaded round of the fully loaded magazine to be displaced within said extension means by contacting a part of the firearm.

3. The drum magazine as in claim 2, wherein:

said follower means is carried by said rotor means to contact a portion of said feed means at certain angular positions of said rotor in either direction of rotation and prevent further rotation beyond said angular positions, so that said portion of the feed means comprises said stationary means.

4. A drum magazine for storing and feeding rounds of ammunition to a firearm, comprising:

drum body means open at least at one end;

a cover removably closing said open end and having a periphery removably attachable to said open end of said body means;

means associated with said body means and said cover to engage the cover on the body means in response to relative rotation therebetween;

locking means on said cover selectably engaging said body means to prevent said relative rotation, so that said cover cannot rotate to disengage the cover and body means;

said periphery of the cover including a cutout portion to expose a lock engaging region of said body means; and

said locking means comprising a first portion movably located on said cover, and further comprising a member extending adjacent said periphery for movement with said first portion and being selectably movable into said cutout portion for engaging said lock engaging region within the cutout portion, thereby preventing the cover from rotating to disengage the body means.

5. A drum cartridge magazine, comprising:

drum body means defining a housing having a front end and a back end, and means closing the front end of said housing;

a back cover removably attachable to the back end of said housing;

a post integral with said front cover means and extending axially inwardly within said cylindrical housing toward said back end of the housing;

axle means retined at the back end of said post and having a member extending beyond the post;

cartridge receiving means disposed within the housing in rotating relation to said post;

said cartridge receiving means having a first axial opening to receive said post and a relatively smaller second opening through which said member extends;

said back cover having an opening through which said member extends;

first locking means removably engaging said member outside said back cover to retain the cover; and

second locking means removably engaging said member inside the cover to retain said cartridge receiving means relative to the post.

6. A drum magazine for storing and feeding rounds of ammunition to a firearm, comprising:

drum body means open at lest at one end;

a cover removably closing said open end and having a periphery removably attachable to said open end of said body means;

means associated with said body means and said cover to engage the cover on the body means in response to relative rotation therebetween;

locking means on said cover selectably engaging said body means to prevent said relative rotation, so that said cover cannot rotate to disengage the cover and body means;

said periphery of the cover including a cutout portion to expose a lock engaging region of said body means; and

said locking means comprising a member selectably movable into said cutout portion for engaging said lock engaging region, thereby preventing the cover from rotating to disengage the body means.

7. A drum cartridge magazine comprising:

drum body means defining a housing;

axle means disposed within said housing;

a cartridge receiving rotor rotatably located on said axle means;

a torsion spring located on said axle means and having a first end operative to engage said rotor at selectably variable locatoins angularly spaced apart on the rotor, so as to impart selectably variable torque preload to said rotor;

said torsion spring having a second end disposed between rotor and axle means for fixed engagement relative to said body means, so that the first end of the torsion spring can impart torque to the rotor relative to the body means;

said rotor having a first side located adjacent siad first end of the torsion spring, and having a second side axially spaced from said first side;

said first side having a plurality of spring engaging openigns radially spaced from said axle means at said selectably variable locations; and

said first end of the torsion spring selectably engaging any of said spring engaging means so as to select the torque applied to the rotor by the torsion spring.

8. A drum cartridge magazine comprising:

drum body means defining a housing;

a post axially disposed within said housing;

a cartridge receiving rotor rotatably located on said post;

a torsion spring located on said post and having a first end operative to engage said rotor at selectably variable locations angularly spaced apart on the rotor, so as to impart selectably variable torque preload to said rotor;

said torsion spring having a second end disposed between rotor and post for fixed engagement relative to said body means, so that the first end of the torsion spring can impart torque to the rotor relative to the body means;

said rotor having a first side located adjacent said first end of the torsion spring, and having a second side axially spaced from said first side;

said first side having a plurality of spring engaging openings radially spaced from said post at said selectably variable locations; and

said first end of the torsion spring selectably engaging any of said spring engaging means so as to select the torque applied to the rotor by the torsion spring.

9. The drum magazine as in claim 8, wherein:

said first and second sides of said rotor are axially spaced apart a first distance adjacent said post, so that the coiled length of said torsion spring is substantially disposed on said post between said rotor sides; and

said spacing between said rotor sides is reduced at the periphery of said rotor to a spacing less than said first distance and operative to receive and support cartridges received on the rotor.

10. A drum magazine for storing and feeding rounds of ammunition to a firearm, comprising:

a body;

a rotor within said body and biased for rotation;

a plurality of round receiving locations defined about the periphery of said rotor to receive and carry rounds along a path within said body;

extension means extending from said body for placement in round feeding relation with a firearm, said extension means having a round-feeding opening and means providing a round feeding path between the extension means and said rotor so that the biased rotation of the rotor serially moves each round to the extension means;

follower means carried by said rotor behind the last round-receiving location to arrive at the extension means, said follower means operatively assuming a radially extended first position to engage the last round and displace that round outwardly from the rotor toward said round-feeding opening when the last round-receiving location is in round feeding relation to the extension means;

said follower means being movable inwardly to a second position to allow the rotor to be moved past the fully loaded position, thereby providing sufficient room to enable a closed first round of the fully-loaded drum magazine to be displaced in said extension means by the presence of a closed bolt in the firearm when the magazine is placed on the firearm;

feed means cooperating with said rotor means to define said round feeding path between said round-receiving locations and said extension means;

stationary means located for engagement by said follower means so as to contact the follower means and limit rotation of said rotor means as the last round-feeding location bears a predetermined relation to said feed means;

said follower means being movable to said first position to feed the last round along said feed means to said extension means;

said follower means being displacable to said second position in response to contacting said stationary means as said rotor moves against said bias to the fully-loaded position to place the first round-receiving location at said feed means, so that the follower means in said second position permits limited further rotation of the rotor means past the fully-loaded position, whereby said further rotation allows the last-loaded round of the fully loaded magazine to be displaced within said extension means by contacting a part of the firearm;

said rotor means comprising a pair of sprockets mounted in mutually spaced apart relation, with recesses formed on the peripheries of said sprockets to provide said round-receiving locations;

said follower means being pivotably mounted on said sprockets behind said last round-receiving location to move between said first and second positions; and

said follower means having a follower surface extending between said sprockets to push the last round up said round feeding path and into said extension means as the rotor sprockets moves the last round-receiving recess past said feed means.

11. The drum magazine as in claim 10, wherein said follower surface is skewed relative to the axis of said rotor means so as to initially contact the front of the last round and thereby feed the last round with front end raised.

12. The drum magazine as in claim 11, wherein the front end of said follower surface is rounded to define a radius presenting a cam surface to the last round, thereby enhancing said feeding of the last round.

13. The drum magazine as in claim 10, further comprising:

a slot formed in each sprocket to receive said follower means for said pivotable movement between said first and second positions;

each said slot including a first portion retaining a mating portion of the follower means for pivotable movement of said follower surface between said first and second positions; and

each said slot including a second portion cooperating with said follower means to define said first and second positions.

14. The drum magazine as in claim 13, wherein:

said follower means includes a pivot member loosely engaged by said first means of the slot in each sprocket; and

said pivot members retaining the follower means against radial separation from the sprockets, yet permitting the follower surface to be withdrawn from the sprockets in a direction substantially parallel to the axis of sprocket rotation.

15. A drum magazine for storing and feeding rounds of ammunition to a firearm, comprising:

a body;

a rotor within said body and biased for rotation;

a plurality of round receiving locations defined about the periphery of said rotor to receive and carry rounds along a path within said body;

extension means extending from said body for placement in round feeding relation with a firearm, said extension means having a round-feeding opening and means providing a round feeding path between the extension means and said rotor so that the biased rotation of the rotor serially moves each round to the extension means;

follower means carried by said rotor behind the last round-receiving location to arrive at the extension means, said follower means operatively assuming a radially extended first position to engage the last round and displace that round outwardly from the rotor toward said round-feeding opening when the last round-receiving location is in round feeding relation to the extension means;

said follower means being movable inwardly to a second position to allow the rotor to be moved past the fully loaded position, thereby providing sufficient room to enable a closed first round of the fully-loaded drum magazine to be displaced in said extension means by the presence of a closed bolt in the firearm when the magazine is placed on the firearm;

feed means cooperating with said rotor means to define said round feeding path between said round-receiving locations and said extension means;

stationary means located for engagement by said follower means so as to contact the follower means and limit rotation of said rotor means as the last round-feeding location bears a predetermined relation to said feed means;

said follower means being movable to said first position to feed the last round along said feed means to said extension means;

said follower means being displacable to said second position in response to contacting said stationary means as said rotor moves against said bias to the fully-loaded position to place the first round-receiving location at said feed means, so that the follower means in said second position permits limited further rotation of the rotor means past the fully-loaded position, whereby said further rotation allows the last-loaded round of the fully loaded magazine to be displaced within said extension means by contacting a part of the firearm;

said follower means being carried by said rotor means to contact a portion of said feed means at certain angular positions of said rotor in either direction of rotation and prevent further rotation beyond said angular positions, so that said portion of the feed means comprises said stationary means;

said feed means comprising a round engaging surface extending to contact rounds carried by said rotor means and to divert said round to said extension means;

said follower means including a follower member which pushes the last round up said round engaging surface toward the extension means; and

said follower means further comprising a cutout portion into which said round engaging surface can enter as said follower member pushes the last round up the round engaging surface with the follower means in said first position.

16. The drum magazine as in claim 15, wherein:

said feed means has a front side on which said round engaging surface is disposed, and a back side; and

said follower member engages said back side as said rotor means moves to the fully loaded position so as to move the follower means to said second position,

wherein the follower member in the second position permits said limited further rotation.

17. A drum magazine for storing and feeding round sof ammunition to a firearm, comprising:

a body;

a rotor within said body and biased for rotation;

a plurality of round receiving locations defined about the periphery of said rotor to receive and carry rounds along a path within said body;

extension means extending from said body for placement in round feeding relation with a firearm, said extension means having a round-feeding opening and means providing a round feeding path between the extension means and said rotor so that the biased rotation of the rotor serially moves each round to the extension means;

follower means removably carried by said rotor behind the last round-receiving location to arrive at the extension means, said follower means operatively assuming a radially extended first position to engage the last round and displace that round outwardly from the rotor toward said round-feeding opening when the last round-receiving location is in round feeding relation to the extension means;

said follower means being movable inwardly to a second position to allow the rotor to be moved past the fully loaded position, thereby providing sufficient room to enable a closed first round of the fully-loaded drum magazine to be displaced in said extension means by the presence of a closed bolt in the firearm when the magazine is placed on the firearm;

feed means cooperating with said rotor means to define said round feeding path between said round-receiving locations and said extension means;

stationary means located for engagement by said follower means so as to contact the follower means and limit rotation of said rotor means as the last round-feeding location bears a predetermined relation to said feed means;

said follower means being displacable to said second position in response to contacting said stationary means as said rotor moves against said bias to the fully-loaded position to place the first round-receiving location at said feed means, so that the follower means in said second position permits limited further rotation of the rotor past the fully-loaded position;

whereby said further rotation allows the last-loaded round of the fully loaded magazine to be displaced within said extension means by contacting a part of the firearm;

said rotor mounted for rotation unobstructed by said stationary means, when said follower means is removed; and

spring means having a member selectably engaging said rotor at any of a plurality of angularly spaced spring engaging locations so as to selectably vary the rotational torque biasing the rotor,

so that the rotor is selectably operable to engage the spring means member at a selected spring engaging location while the rotor initially is in an unbiased position, permitting the rotor to be rotated against the spring means to wind the spring means before said follower means is inserted in the rotor to contact said stationary means and limit rotation caused by the spring means.

18. A drum magazine for storing and feeding rounds of ammunition to a firearm, comprising:

a body including extension means placeable in round feeding relation with a firearm;

a rotor mounted within said body for rotation, and defining

a plurality of round receiving locations about the periphery of said rotor to receive and carry rounds along a path within said body;

spring means having a member selectably engaging for and biasing said rotor at any of a plurality of angularly spaced spring engaging locations so as to selectably vary the rotational torque biasing the rotor so that the rotor can engage the spring means member at a selected spring engaging location while the rotor initially is in an unbiased position, permitting the rotor to be rotated against the spring means to wind the spring means,

feed means cooperating with said rotor to define a round feeding path between said round-receiving locations and said extension means;

follower means removably carried by said rotor behind the last round-receiving location to arrive at said feed extension means, said follower means operatively assuming a radially extended first position to engage the last round and displace that round outwardly from the rotor toward said round-feeding opening when the last round-receiving location is in round feeding relation to the extension means; and

stationary means associated with said body and located for engagement by said follower means when carried by said rotor, so that said follower contacts the stationary means and limits rotation of said rotor as the last round-feeding location bears a predetermined relation to said feed means; and

said rotor being rotationally unobstructed by said stationary means when said follower means is removed from the rotor,

so that the follower means can be inserted in the rotor to limit rotation in response to the spring means, after the rotor is rotated to wind the spring means.