[0001] This invention relates to a drum magazine for a gun.
[0002] Known drum magazines tend to suffer from friction losses caused by friction between
the cartridges in the magazine and the internal surfaces of the magazine. Although
it might be expected that there would be rolling friction with the cartridges, in
fact, there is no rolling friction, but simply sliding friction.
[0003] One known drum magazine is the Thompson which is capable of holding up to fifty rounds
and is described in "The World's Sub-machine Guns (Machine Pistols)", Volume 1 by
Thomas B. Nelson, International Small Arms Publishers, Cologne, West Germany, first
edition, second printing June 1964, pages 51 to 53. In the Thompson magazine there
is a spiral guide in which the cartridges are arranged in, effectively, rows and the
cartridges are swept out of a feed throat by six radial, rotating, arms driven by
a spring which sweep all of the cartridges simultaneously around the rows. The friction
in such a magazine is very great and it has been found that it is not practical to
provide more than two spiral rows. However, it is possible to increase the capacity
of such a magazine by increasing the drum diameter without increasing the number of
rows, but the magazine then becomes undesirably bulky.
[0004] In an attempt to reduce the friction losses, a further known magazine is the Soumi
drum magazine, described in the forementioned book at pages 562 - 565 and shown in
Figures 1 and 2 of the accompanying drawings. In the Soumi magazine, a circular, pan-like
housing 1' is provided having a rotatable base plate 2' upon which the cartridges
sit in paths 3', 4' defined by concentric guides 5', 6' and the inner surface of the
housing 1' respectively and a bridge 7' linking the paths 3', 4'; the guides 5', 6'
and bridge 7' being rotatable with the base plate 2'. The housing has a throat 8',
a feed ramp 9' and a stop 10' with which a lug 11' mounted on the guide 5' co-operates.
A coil spring (not shown) beneath a rotor 12' drives the rotor and an associated pivotal
pusher 13'. The cartridges are referenced 15' and the cartridge adjacent the lug 11'
is referenced 16'.
[0005] In operation, the spring drives the rotor 12' and pusher 13' which applies pressure
in the direction of arrow-headed line A. through all of the cartridges up to the lug
11' so that it is the pressure on cartridge 16' which drives the guides 5', 6' and
the base plate 2'. The pressure on lug 11' thus urges the cartridges up the ramp 9'
and through the feed throat 8'. There is, thus, frictional resistance between the
cartridges in the outer row pushing outwardly against guide 1', although the inner
row of cartridges is rotatably carried by the base plate 2' for the first partial
revolution until the cartridges in the outer row are ejected through the throat 8'
and this frictional resistance is less than that associated with the Thompson magazine.
The friction is less than with the Thompson magazine because the guides 5', 6' that
form the inside and outside diameter of the innermost row of ammunition moves with
the ammunition for the first revolution. During that revolution, the outer row is
driven out of the feed throat, but its inside diameter guide moves with it so that
the outer row has only one half the sliding friction contact of the Thompson type
and the inner row has none at all. When, however, the lug 11' engages the stop 10',
the bridge 7' from the inner path 3' to the outer path 4' is in alignment with the
feed throat 8' and the base plate 2' no longer rotates so that the inner row of cartridges
abrade against the stationary guide surfaces, thereby producing a high friction force
which is similar to that of the Thompson magazine. Additionally, because the pusher
13' exerts pressure on the last cartridge 15' in the magazine to drive all the other
cartridges and because the cartridges are circularly arranged, the cartridges are
forced outwardly against the guide surfaces, thereby increasing friction. It has,
again, been found impractical to increase the number of paths to improve the capacity
of such a magazine and if increased capacity is sought it is, once again, necessary
to increase the drum diameter undesirably.
[0006] A further disadvantage of the forementioned drum magazines is that they can only
readily be filled with cartridges by removing the circular planar cover, since they
can only be filled through the feed throat by sliding cartridges between the feed
lips in the axial direction of the housing.
[0007] The present invention seeks to provide a drum magazine of compact dimensions and
of relatively large capacity which exhibits less friction to cartridge movement than
the drum magazines described above.
[0008] According to one aspect of this invention there is provided a drum magazine for a
gun including a housing having a peripheral wall defining a circularly cross-section
interior, a feed throat extending through the said wall for releasing cartridges from
the housing characterised in that said feed throat provides an opening in said peripheral
wall, said opening having a first side and a second side with an outer extremity of
said first side of said opening being provided with a fixed lip extending over the
feed throat and said second side of said opening being provided with a spring biassed
movable lip biassed in a direction outwardly of the magazine, the spacing between
the lips being dimensioned so that a cartridge leaving the feed throat can only be
slid therefrom in the direction of the housing axis and in no other direction when
the magazine is mounted on a gun.
[0009] Preferably the movable lip is a pivotal lip which has an axis about which said pivotal
lip moves which is substantially parallel with an axis of said magazine for enabling
a cartridge pressed on the outer surface of said pivotal lip to rotate the pivotal
lip toward the feed throat to permit access of the cartridge to the feed throat in
a direction substantially perpendicular to the housing axis.
[0010] Advantageously the pivotal lip has a tail portion which, when the magazine is in
a gun receiver, prevents the pivotal lip from rotating.
[0011] Preferably the fixed lip is tapered in a direction to permit the nose of a cartridge
to be directed upwardly away from the feed throat.
[0012] Preferably including a neck partially bounding the feed throat in which holes are
spaced on one side thereof in the direction of the housing axis, and a cover of the
housing having a radial key thereon, whereby the combination of holes and key are
arranged to hold the magazine on a gun receiver.
[0013] In a currently preferred embodiment there is provided at least two rotatable concentric
sprocket means, an outer periphery of the sprocket means each having a plurality of
serrations arranged to nest a plurality of cartridges, the serrations of the inner
sprocket means being spaced from the inner surface of the next adjacent outer sprocket
means by substantially the same distance as the serrations of the outermost sproeket
means are from the housing interior peripheral wall a cartridge feed aperture in each
sprocket means except the innermost for permitting cartridges to pass from the inner
sprocket means to the outer sprocket means and feed ramp means arranged to guide cartridges
from each of the sprocket means to the feed throat, the feed ramp means comprising
a ranp extending from the feed throat for scooping cartridges from the outermost sprocket
means and a further ramp on one major side of the cartridge feed aperture in the sprocket
means extending inwardly for scooping cartridges from the adjacent inner sprocket
means, and another ramp on the other major side of the cartridge feed aperture in
the sprocket means for guiding the cartridges along said further ramp, a guide being
provided on the said ramp and said further ranp to tilt a cartridge passing therealong
whereby cartridges pass along the ramps in an inclined, nose-up condition.
[0014] According to a further aspect of this invention there is provided a detachable cartridge
drum magazine for a
gun including a housing having a peripheral wall defining a circularly cross-section
interior, a feed throat extending through the said wall for releasing cartridges from
the housing to provide an opening in said peripheral wall, characterised by said opening
having a first side and a second side with an outer extremity of said first side of
said opening being provided with a movable lip which is pivotally biassed toward a
closed position to act as a one way valve, and said second side of said opening being
provided with a fixed lip partially extending over the feed throat, means for preventing
a cartridge being ejected from between the fixed lip and the movable lip except by
sliding in the axial direction of the housing when the magazine is mounted on a gun,
and said preventing means permitting said movable lip to be pivoted against said bias
to an open valve position to permit cartridges to be fed into the feed throat in a
direction perpendicular to the housing axis.
[0015] The invention will now be described, by way of example, with reference to the accompanying
drawings, in which
Figure 3A shows in partial section a schematic view of a drum magazine in accordance
with this invention,
Figure 3B is a cross-section along double arrow-headed line 3B-3B of Figure 3A, with
the pusher removed,
Figure 3C is a view in the direction of double arrow-headed line 3C-3C of Figure 3B
showing the arrangement of the stops for the intermediate and outer sprockets but
with the cartridges removed,
Figure 4 is a view similar to Figure 3A but with the parts in different positions,
Figure 5A is a view similar to Figure 3A but with the parts in a different position,
Figure 5B is a detail of the encircled portion arrowed 5B in Figure 5A drawn to a
larger scale and incorporating, in phantom lines, a part of the magazine well of the
gun,
Figure 6 is a view similar to Figure 3A but with the parts in a different position,
Figure 7A is a view similar to Figure 3A but with the parts in a different position,
Figure 7B is a view along double arrow-headed line 7B-7B of Figure 7A,
Figure 8A is a top view of the housing,
Figure 8B is a view in the direction of arrow-headed line 8B of Figure 8A,
Figure 8C is a cross-sectional view along double arrow-headed line 8C - 8C of Figure
8B,
Figure 9A is a side view of an outer sprocket,
Figure 9B is a cross-sectional view along double arrow-headed line 9B - 9B of Figure
9A,
Figure 9C is a view in the direction of arrow-headed line 9C in Figure 9A,
Figure 10A is a side view of an intermediate sprocket,
Figure 10B is a view in the direction of arrow-headed line 10B of Figure 10A,
Figure 10C is a view in the direction of arrow-headed line 10C of Figure 10A,
Figure 11A is a plan view of an inner sprocket,
Figure 11B is a view along double arrow-headed line 11B - 11B of Figure 11A,
Figure 12A is a top plan view of a cover,
Figure 12B is a cross-sectional view along double arrow-headed lines 12B - 12B of
Figure 12A,
Figure 12C is a view in the direction of arrow headed-line 12C of Figure 12A, and
Figure 13 is a partial view of an alternative last round stop actuator.
[0016] In the Figures 3A - 13 like references denote like parts.
[0017] In the Figures 3A, 4, 5A, 6 and 7A the cartridges are denoted by the prefix C so
it will be seen from Figure 3A that in the fully loaded position the magazine holds
100 cartridges.
[0018] The drum magazine shown in Figures 3A to 7B has a circularly cross-sectioned, pan-shaped
housing 40 having a cover 41 within which is concentrically mounted an outer sprocket
42, an intermediate sprocket 43, and an inner sprocket 44. The drum, cover and each
of the sprockets are made from moulded plastics and each of the sprockets is spool-shaped
having a central tubular body and at each end of the body is a radially extending
flange each having a like number of serrations around the outer periphery for holding
cartridges. The serrations in the flanges adjacent a base 404 of the housing have
a greater radial extent than the serrations in the arms adjacent the cover 41 to allow
for the taper of a cartridge and so that the cartridge axes are approximately parallel
to the axis of the housing. The inner sprocket 44 has serrations to hold each of cartridges
C1 - C24, the intermediate sprocket 43 has a serration to hold each of cartridges
C27 - C57 and the outer sprocket 42 has a serration to hold each of cartridges C60
- C98. In the assembled position, shown in Figures 3A - 7B, the sprockets are located
in the housing 40 so that feed ramps 434, 441 on the housing, 455, 455' on the outer
sprocket, and 471, 471' on the intermediate sprocket adopt the positions shown in
Figure 3A and the feed ramp 434 extends to the base of cartridge C98, the feed ramp
455' extends to the base of cartridge C58 and the feed ramp 471' extends to the base
of cartridge C25. In this way the feed ramps are effective to scoop up the cartridges
in the sprockets with which the ramps are associated and the ramps 441, 455', 471'
act as guides for the cartridges. Mounted to be fixed on the axis of the housing 1
is a nylon spindle 45 secured to the housing and cover respectively by screws 400,401.
The spindle has an ear 402 to which is secured one end of a sheet metal clock-type
torsion spring 46, the other end of the spring 46 being secured to an aperture 403
in the inner sprocket 44.
[0019] As best shown in Figures 7B and in phantom lines in Figure 11A, a pusher 47 is mounted
on the inner sprocket 44. The pusher 47 has a spindle 405 positioned between the arms
of the inner sprocket and pivotally mounted on the spindle 405 is a U-shaped arm 406
with the limbs of the U-shape within the confines of the inner sprocket flanges and
adjacent a respective flange. The free ends of the U-shape are secured to the spindle
405 and a rod 407 having the approximate shape of a cartridge is welded to the base
of the U-shape. The rod 407 has a tail 408 which is locatable in a serration of the
inner sprocket and a bevelled top portion 409 (as viewed in Figure 7B) remote from
the tail 408 to facilitate a bolt of the gun to which the magazine is secured to ride
over the rod 407. Connected to the spindle 405 between the U-shaped arm 406 and the
wing of the inner sprocket adjacent the cover 41 is a last round stop actuator 48
comprising a spring arm 413 which is biassed toward the cover 41 and a button 414
which may contact a mechanism within a gun receiver to which the magazine is mounted
so that when the last cartridge from the magazine is fired the bolt mechanism can
be held in the cocked position. It is in the event that the last round stop actuator
fails to operate the mechanism within the gun receiver that the bevelled portion 409
is provided so that the bolt will strike the pusher obliquely to the bevel. The tail
408 of the pusher is extended so that it may co-operate with a sprocket latch, as
will be described later herein.
[0020] The housing 40 has a feed throat 415 defined by a neck 416 having longitudinal sides
in the axial direction of the housing and which is arranged to be located in the magazine
well of a gun. The neck 416 has, on its right hand side (as viewed in Figures 3A and
4 - 7A),a pivotal lip 417 and on its left hand side an arcuate, fixed lip 418 extending
over the feed throat. Referring particularly to Figure 5B, the neck of the magazine
is shown located in a well of a gun (the well being shown in phantom lines). The pivoting
lip 417 is mounted on an axle 419 and has an arm 420 with an arcuate upper surface
421, generally the same radius as a cartridge, and a tail 422 of such a length that,
when the magazine is inserted into the well of a gun, the tail prevents rotation of
the lip 417 so that it is not possible for the lip 417 to adopt the position shown
in solid line in Figure 5B when . mounted in the gun well. The lip 417 is biassed
by a spring (not shown) so that the bottom of the lip (as viewed in Figure 5B) is
normally horizontal, as shown in phantom lines. The distance between the lips 417
and 418 is arranged so that with the lip 417 spring biassed in a clockwise direction
(as shown in Figure 4 for example and in Figure 5B in phantom lines) it is not possible
for a cartridge to be removed from above the lips so the cartridges may not fall out
of the magazine. When the magazine is removed from the gun the cartridge may, however,
be unloaded from the magazine in a direction perpendicular to the cartridge longitudinal
axis by depressing lip 417. In use, the cartridges are axially slid from the magazine
by a bolt of the gun. A latching mechanism is provided to secure the magazine to the
well of the gun and,conveniently, such a mechanism comprises a pair of pins which
may be slidably mounted through one of the walls of the magazine well into co-operating
holes in the neck 416 of the housing, these holes being referenced 423 in Figure 8A
and one of the pins being shown in phantom lines in Figure 5B.
[0021] The pan-shaped housing 40, shown in Figure 8A, 8B and 8C has an open top 424 to which
the cover 41 is connected by internally screw threaded bosses 425 and located by pins
426 on each side of the neck 416. The housing 40 has a large internal diameter portion
427 for accommodating the body of the cartridge in the outer sprocket and a reduced
internal diameter portion 428 in the region of the nose (bullet) portion of the cartridge
and the portion 428 is connected to a base 429. The base has a circular protrusion
430, the interior of which acts as a bearing surface- upon which the outer sprocket
42 and intermediate sprocket 43 rotate. In this respect, the concentric protrusion
430 has a radially outer side 444 to concentrically locate the outer sprocket 42 and
an inner side 445 to locate the intermediate sprocket 43 in a concentric fashion.
The base 429 is dished to provide an inner boss 431 providing a bearing surface 432
and a concentric guide surface 433 for the inner sprocket 44. On the axis of the drum
in the boss 431 is a hole for the screw 400. The fixed lip 418, as best seen in Figure
8A, is tapered inwardly of the housing so as to permit cartridges which are trapped
by the lips 417, 418 to be tilted such that the bullet is angled upwardly, the relieved
portion of the fixed lip 418 permitting the cartridge body to rise slightly higher
than the region of the cartridge toward the cannelore. This allows the cartridge to
assume an ever increasing upward angle as it is driven in operation forwardly by the
bolt so that it can enter the chamber smoothly without the base or cannelore end being
forced downwardly. Such action is in distinction to the usual feed path of conventional
magazines where, as the cartridge is driven forwardly, the bullet end is forced upwardly
as it enters a feed ramp and the base end goes downwardly. This is because the forward
corner of the conventional feed lip contacts the center, body, portion of the cartridge
and acts as a fulcrum so that as the bullet end rises the base end is forced downward,
thus causing the other cartridges in the magazine to be pushed downward in the magazine.
In magazines of large capacity such reversing action (driving the bulk of the cartridges
backwardly) requires substantial short term energy and has the undesirable effect
of retarding bolt motion.
[0022] On the side of the feed throat 415 adjacent the fixed li
p 418 is a feed ramp 434 having at its outer side a notch 435 to accommodate the serrations
of the outer sprocket and at the inner side of the feed ramp 434 is a web guide 436
for the cartridges. Also provided on the same side of the throat as the fixed lip
is a stop 437 for the outer sprocket. The pivoting lip 417 is located in a cutout
defined by side walls 438 and 439 and a bottom part 440, the side wall 439 having
an internal ramp portion 441 which also acts as a guide for feed ramp 434. A hole
442 in both side walls 438, 439 is for the axle 419 of the pivoting lip 417. Both
sides of the feed throat 415 have notches 443 which, in operation, abut against respective
stop pins in the well of the gun to limit the extent of insertion of the magazine
into the receiver.
[0023] As shown in Figure 8B, the internal diameter portion 428 has a recess 446 for co-operating
with a latch 447 provided on the outer sprocket. Alternatively, instead of a recess,
an aperture could be provided.
[0024] Referring now to Figures 9A, 9B and 9C, the outer sprocket 42 has a tubular body
448 with flanges 449, 450 each having a like number of serrations 451 in which are
located, between the flanges 449, 450 cartridges. For reasons discussed earlier, the
serrations in flange 449 have a greater radial extent than those in flange 450. The
body 448 has a reduced diameter portion 452 which sits within the internal diameter
portion 428 of the housing and a concentric bearing surface 453 which engages the
internal side of the protrusion 430. The body 448 has a feed aperture 454 to permit
cartridges from the intermediate and inner sprockets to pass therethrough. The feed
aperture 454 has feed ramps 455, 455' and a guide ramp 456 arranged to tilt the cartridge
so that the bullet portion is inclined outwardly of the feed aperture 454. Located
in the reduced diameter portion 452 is a stop 457 presenting a stop surface 458 for
contacting the stop 437 of the housing and a further stop surface 459 for co-operating
with a stop on the intermediate sprocket. The wall of the portion 452 has an aperture
460 shaped to house the latch 447 and to form a lip 461 against which a claw on a
latch 462, connected to the intermediate spool, co-operates. Transversely to the aperture
460 is a hole 463 in a boss for a pin pivotally locating the latch 447. The reduced
diameter portion 452 is arranged to locate the neck of a cartridge so as to maintain
the cartridge with the required amount of tilt in the magazine. The latch 447 is bent
into the shape of a dog leg so that it is able to overlap the latch 462.
[0025] The intermediate sprocket 43, shown in Figures 10A, 10B and 10C, is similar to the
outer sprocket 42 and has a body 464 with a reduced diameter portion 465 and serrated
flanges 466 and 467 between which cartridges are held. The radial extent of the serrations
in flange 466 is greater than that of those in flange 467 for the reason discussed
earlier. The end face of the reduced diameter portion 465 has a bearing surface 468
for rotating on the surface 430 of the housing and a recessed annular part 469, the
inner periphery of which acts as a concentric guide surface to abut the inner side
445 of the housing. The intermediate sprocket has a feed aperture 470 having feed
ramps 471, 471' and in which is disposed a cartridge 499 that is tilted by a guide
ramp 472, as described in relation to the outer sprocket 42. The guide ramp 471' extends
interiorally of the body 464. A stop 473 having a stop surface 474 for contacting
the stop 459 on the outer sprocket 42 is provided on the reduced diameter portion
465 and in the side wall of the reduced diameter portion 465 is an aperture 475 for
the latch 462 and a hole 476 is provided in a boss for a pin locating the latch 462.
[0026] The inner sprocket 44, shown in Figures 11A and 11B, has a body 477' with serrated
side flanges 477, 478 and the body 477' has the rectangular aperture 403 within which
one end of the spring 46 is located. The radial extent of the serrations in flange
477 is greater than that in the flange 478 to tilt the cartridge (shown in phantom
lines). In the position between which cartridges C1 and C25 (shown in phantom lines)
are located is a notch 479 in the arm 477 within which the rod 407 of the pusher is
locatable. A hole 480 is provided in each of the arms 477 and 478 for the spindle
405 of the pusher. The latches 447 and 462 are both formed from strip material and,
as best shown in Figure 4, both mounted on a respective pivot 481 and both biassed
by a respective torsion spring 482, one end of which engages with an edge of slot
460, 475 respectively and the other end of which is bent into an L-shape and engages
a tang 483, 484 respectively of the latches 447 and 462. At the end of the latches
447, 462, remote from the tangs, is a finger 485; 486 respectively and a protruding
ear 487, 488 respectively; the ear 487 engaging with a lip 489 on the recess 446 of
the housing 40 and the ear 488 being arranged to engage with the lip 461 on the outer
sprocket 42 (as shown in Figure 6). The fingers 485 and 486 are both shaped to be
inserted between cartridges C28 and C29 and between cartridges C2 and C3 respectively
and to bear against cartridges C28 and C2 respectively. The tangs 483 and 484 have
a radius portion which is arranged to be engaged by cartridge C26 and the rod 407
of the pusher 47 respectively.
[0027] Referring now to Figures 12A, 12B and 12C, the cover 41 is a moulding made from clear
plastics having a circular shape with six holes 490 located in protrusions of the
cover for securing the cover to the housing 40. The cover has an axial hole 491 formed
with notches 492 which act as a keyway for the spindle 45 and prevent the spindle
45 from rotating. The region surrounding the hole 491 is dished to provide a recess
for the head of screw 401 and the underside of the cover has concentric ring slots
493, 494 for the flanges 450, 467 of the outer and intermediate sprockets respectively.
To facilitate the provision of the slots 493, 494 the cover is locally thickened.
Shown symmetrically about the horizontal axis in Figure 12A is a key 410 formed from
ribs 411 with a root radius 412 between the ribs and the planar part of the cover.
The cover has a neck 495 corresponding in part to the neck 416 of the housing and
positioned partially down the neck and extending toward the hole 491 is a guide cover
496 which is chamfered toward the cover outer surface (as best shown in Figure 7B)
to guide the actuator 48 in and out of the housing. The region 497 on each side of
the ribs 411 is relieved to provide an improved depth of the ribs 411 upon which a
keyway on the gun receiver may engage and because of slots 493 and 494,arcuate apertures
498 are formed. The guide cover 496 is recessed to provide a slot 496' of such depth
that the cover 496 clears a normally provided last round stop in the gun receiver.
The confluence of the relieved portion 497 and the thickened portion of the cover
has a bevelled edge 497' to ease the location of the magazine onto the receiver keyway.
The neck 495 is of such a length that it partially covers a top most cartridge to
prevent the cartridge from moving rearwardly. Holes 490' are provided on the neck
495 within which the pins 426 on the housing are located and a protruding pin 491'
extending on the underside of the cover forms part of the feed ramp for the cartridges.
A water drain hole 492' is provided on the inside surface of the cover.
[0028] In the position shown in Figure 3A, the latches 447 and 462 are held downwardly by
cartridges C64 and C30 respectively and the fingers 485 and 486 respectively are,
thus, forced between cartridges C28, C29 and C2, C3 respectively. The action and purpose
of the fingers 485 and 486 will be described later.
[0029] In operation, the spring 46 drives the sprockets in an anti-clockwise direction (as
viewed in the Figures 3A, 4, 5A and 6) so that starting with the magazine fully loaded,
as shown in Figure 3A, cartridge C2 pushes on finger 486 which, because latch 462
is connected by pivot 481 to the intermediate sprocket 43, causes sprocket 43 to rotate
in an anti-clockwise direction. The turning effort of intermediate sprocket 43 is,
thus, applied to cartridge C28 which, in turn, applies a pressure through finger 485
of latch 447 to the outer sprocket 42 which, thus, also is rotated in an anti-clockwise
direction.
[0030] The rotation of the outer sprocket 42 causes cartridge C98, located in a serration
of the flanges 449, 450, to push against cartridges C99 and C100 and the cartridge
C100 is prevented from being ejected from the throat 415 of the magazine by the lips
418, 417. It will, thus, be seen that the dimension between the lips 417, 418 is extremely
important.
[0031] When the magazine is inserted into a gun magazine well (as shown in Figure 5B) the
magazine is held in position by pins (shown in phantom lines) which locate in the
holes 423. Assuming that the bolt has been cocked, then on releasing the gun trigger
the bolt moves forwardly toward the barrel and a stripping lug associated with the
bolt slidingly removes the cartridge C100 from the lips 417, 418 in a direction perpendicular
to the plane of the Figure 3A, i.e., in a direction from right to left in Figure 3B
which is also in the direction of the housing axis. The cartridge C100 is, thus, pushed
from the magazine into the chambers. Due to continued force being exercised by the
spring 46 on the sprockets, so the sprockets rotate in an anti-clockwise direction
and cartridge C99 is moved upwardly to be held by the lips 417, 418 and cartridge
C98 is, thus, scooped out of the serrations in flanges 449, 450 by the ramps 434.
This action continues until the outer sprocket 42 has given up all of its cartridges
C98 - C60 and the stop surface 458 on outer sprocket 42 contacts stop 437 on the housing
40 (as shown in Figure 3C). The positions of the stops 437 and 457 are such that the
feed ramps 434 and 441 on the housing align with feed ramps 455' and 455 respectively
of the outer sprocket 42. Whilst the outer sprocket was rotating and when cartridges
C64, C63, C62 are de-nested and move up the ramp 434, so the latch 447, which has
heretofore been held depressed by cartridges C64, C63, C62 is released and is biassed
by spring 482 so that the ear 487 abraids the internal diameter portion 427 of the
housing and continued rotation is such that when the stop surface 458 abuts stop 437
so the ear 487 engages lip 489 and the outer sprocket 42 is prevented from rotating
clockwise. The parts of the magazine are, thus, in the position shown in Figure 4.
[0032] Continued feeding of the cartridges from the feed lips causes those cartridges on
the intermediate sprocket 43 to be expended and the arrangement to adopt the position
shown in Figure 5A with the cartridge C30 being scooped by ramp 455' to move up the
feed ramps 455', 455. Continued rotation of the inner sprocket 44 causes the stop
surface 474 of stop 473 on the intermediate sprocket 43 to abut the stop surface 459
on the outer sprocket (as shown in Figure 3C) and the feed ramps 471', 471 of the
intermediate sprocket 43 to align with the feed ramps 455', 455 respectively of the
outer sprocket 42 (as shown in Figure 6) and the latch 462 is spring biassed so that
the ear 488 engages with the lip 461 on the outer sprocket 42.
[0033] Continued release of the cartridges causes further rotation of the inner sprocket
44 so the cartridges C24 - C1 pass up the feed ramps 471', 471, 455', 455, 434 and
441 and because there are no further cartridges to push cartridges C6 - C1 up the
feed ramps so the rod 407 of the pusher 47 is scooped up by the feed ramp 471' to
push these cartridges up to the feed lips, the length of the arm 406 being such that
the rod is able to extend to the feed lips 417, 418 (as shown in Figures 7A and 7B).
Connected at one side of the arm 406 is the last round stop actuator 48 and as the
pusher 47 extends up the feed ramp so the spring arm 413, which is biassed against
the guide cover 496 on the cover 41, moves with the arm upwardly and outwardly through
the slot 496' in the cover. Until the pusher starts to move, the last round stop actuator
48 is mounted alongside the U-shaped arm 406 of the pusher. The action of the last
round stop actuator button 414 is to move a bolt latch in the gun to latch the bolt
assembly in an open position so that when the next magazine is inserted in the gun
the bolt is already cocked.
[0034] To load th
2 magazine, cartridges are inserted through the feed throat 415 in a direction perpendicular
to the housing axis so that the cartridges are inserted into the upper surface 421
of the spring biassed pivoting lip 417 and downward pressure on the cartridges causes
the pusher 407 to be partially depressed and the lip 417 to be rotated to the position
shown in solid lines in Figure 5B. After loading six cartridges the pusher 47 is laid
in its rest position on the inner sprocket-and the insertion of further cartridges
cause the cartridge C1 to be nested in the first of the serrations on the inner sprocket
44. The action of depressing the pusher 47 is, of course, against the force exerted
by spring 46 and as the cartridges C1 - C24 are nested in their associated serrations
so the inner sprocket 44 is rotated in a clockwise direction. When cartridge C30 is
inserted in to the feed lips the pusher tail 408 contacts tang 484 on the latch 462
and thereby rotates the latch 462 so that the ear 488 is dis-engaged from the lip
461. The intermediate sprocket 43 is, thus, free to rotate in a clockwise direction
and,with the insertion of cartridges C31 and C32,adopts the position shown in Figure
5A. Referring to Figure 5A, the insertion of cartridges C31 and C32 causes cartridges
C28, C29 to depress the latch 462 so that the finger 486 is inserted between the cartridges
C2, C3 (see Figure 4). Continued clockwise rotation of the intermediate spool 43 and
inner spool 44 causes the latch 462 to be fully depressed by cartridges C30, C29,
C28 and the finger 486 to be firmly pushed between cartridges C2, C3, and to bear
against cartridge C2.
[0035] The function of the finger 486 is as follows:
With the parts shown in the positions of Figure 5A the spring 46 exerts a pressure
through cartridges C24, C25 and C26, causing cartridge C26 to be forced against the
inner wall of the outer sprocket 42, thus resulting in undesirable friction. However,
with the downward pressure of cartridge C30 on the latch 462, as shown in Figure 4,
so finger 486 pulls cartridge C2 and, thus, the inner sprocket 44 in a clockwise direction
relative to the intermediate sprocket 43. In this manner, the pressure from spring
46 upon cartridges C24, C25, and C26 is released and the cartridges C25, C26 have
a small amount of freedom within the feed ramps 471' and 471 and the forementioned
undesirable friction is removed.
[0036] Continued feeding of cartridges into the feed throat 415 causes both inner sprocket
44 and intermediate sprocket 43 to be rotated in a clockwise direction until cartridge
C26 is rotated so that it abuts the tang 483 on latch 447. The latch 447 is, thus,
rotated against the bias of its associated spring 482 so that the ear 487 is moved
out of abutting contact with the lip 489 and, thus, permitting the outer sprocket
42 to rotate in a clockwise direction. The position shown in Figure 4 is where the
cartridge C26 is about to abut the tang 483. Continued filling with cartridges is
such that the cartridges C64, C63, C62 force the finger 485 of latch 447 to pull the
cartridge C28 in a clockwise direction and, hence, the intermediate sprocket 43 is
moved in a clockwise direction relative to the outer sprocket 42 and the cartridges
C57, C58 and C59 are freed from a tight fit against one another, in similar manner
to the action of finger 486 upon cartridges C24, C25 and C26. Thus, the cartridges
C58 and C59 have a small degree of freedom within the feed ramps 455' and 455 and
undesirable friction between C59 and the inner wall of the housing 40 is eliminated.
Thus, all of the cartridges in the magazine are loosely held in the serrations or
feed ramps and frictional forces are reduced to a minimum. The magazine is completely
filled by inserting cartridges up to C100 and the magazine is then in the position
shown in Figure 3A.
[0037] It is to be understood that the provision of the latches 447 and 462 is not necessary
to the working of the invention, although they are considered to be extremely desirable
for the dual function they each perform. In this respect, the ears 487, 488, in conjunction
with lips 489, 461 respectively, prevent rotation of sprockets 42, 43 respectively
to permit the magazine to be loaded through the feed throat 415. Secondly, the fingers
485, 486 of the latches permit drive from the intermediate sprocket to the outer sprocket
to be through the latch 447 and from the inner sprocket to the intermediate sprocket
through the latch 462 respectively, thereby enabling all of the cartridges in the
magazine except cartridges C100, C99 to have a small amount of freedom of movement
within the magazine. Having described the function and operation of the latches, it
will be realised by those skilled in the art that latches having similar functions,
although possibly requiring differing components to perform each of the two functions
could be designed, with advantage, for use with the Soumi-type magazine.
[0038] Referring now to Figure 13, there is shown an alternative form of last round stop
actuator in which a compression spring 413
1 and plunger 4l4' are inserted in a bore of the rod 407. The action of the plunger
414' is such that as the rod 407 moves up the feed ramp so the plunger 414' is extended
by the force of spring 413' and when the arm 406 is fully extended so the plunger
414' abuts the last round stop mechanism in the gun receiver.
1. A drum magazine for a gun including a housing (40) having a peripheral wall (427)
defining a circularly cross-section interior, a feed throat (415) extending through
the said wall for releasing cartridges from the housing characterised in that said
feed throat (415) provides an opening in said peripheral wall (427), said opening
having a first side and a second side with an outer extremity of said first side of
said opening being provided with a fixed lip (418) extending over the feed throat
and said second side of said opening being provided with a spring biassed movable
lip (417) biassed in a direction outwardly of the magazine, the spacing between the
lips being dimensioned so that a cartridge leaving the feed throat can only be slid
therefrom in the direction of the housing axis and in no other direction when the
magazine is mounted on a gun.
2. A drum magazine as claimed in claim 1, characterised in that the movable lip is
a pivotal lip (417) Which has an axis about which said pivotal lip moves which is
substantially parallel with an axis of said magazine for enabling a cartridge pressed
on the outer surface of said pivotal lip to rotate the pivotal lip toward the feed
throat to permit access of the cartridge to the feed throat in a direction substantially
perpendicular to the housing axis.
3. A drum magazine as claimed in claim 2, characterised in that the pivotal lip (417)
has a tail portion (422) which, when the magazine is in a gun receiver, prevents the
pivotal lip from rotating.
4. A drum magazine as claimed in any preceding claim, characterised in that the fixed
lip (418) is tapered in a direction to permit the nose of a cartridge to be directed
upwardly away from the feed throat.
5. A drum magazine as claimed in any preceding claim, characterised by further including
a neck (416) partially bounding the feed throat in which holes (423) are spaced on
one side thereof in the direction of the housing axis, and a cover (41) of the housing
having a radial key (410) thereon, whereby the combination of holes and key are arranged
to hold the magazine on a gun receiver.
6. A drum magazine as claimed in any preceding claim, characterised in that there
is provided at least two rotatable concentric sprocket means (42, 43, 44), an outer
periphery of the sprocket means each having a plurality of serrations (451) arranged
to nest a plurality of cartridges, the serrations of the inner sprocket means (44)
being spaced from the inner surface of the next adjacent outer sprocket means (43)
by substantially the same distance as the serrations of the outermost sprocket means
(42) are from the housing interior peripheral wall (427), a cartridge feed aperture
(454, 470) in each sprocket means except the innermost for permitting cartridges to
pass from the inner sprocket means (44) to the outer sprocket means (42) and feed
ramp means (434, 441, 455, 455', 471, 471') arranged to guide cartridges from each
of the sprocket means to the feed throat (415), the feed ramp means comprising a ramp
(434) extending from the feed throat (415) for scooping cartridges from the outermost
sprocket means (42) and a further ramp (455', 471') on one major side of the cartridge
feed aperture in the sprocket means extending inwardly for scooping cartridges from
the adjacent inner sprocket means, and another ramp (455, 471) on the other major
side of the cartridge feed aperture in the sprocket means for guiding the cartridges
along said further ramp, a guide being provided on the said ramp and said further
ramp to tilt a cartridge passing therealong whereby cartridges pass along the ramps
in an inclined, nose-up condition.
7. A detachable cartridge drum magazine for a gun including a housing (40) having
a peripheral wall (427) defining a circularly cross-section interior, a feed throat
(415) extending through the said wall for releasing cartridges from the housing to
provide an opening in said peripheral wall, characterised by said opening having a
first side and a second side with an outer extremity of said first side of said opening
being provided with a movable lip (417) which is pivotally biassed toward a closed
position to act as a one way valve, and said second side of said opening being provided
with a fixed lip (418) partially extending over the feed throat (415), means (422)
for preventing a cartridge being ejected from between the fixed lip and the movable
lip except by sliding in the axial direction of the housing when the magazine is mounted
on a gun, and said preventing means (422) permitting said movable lip (417) to be
pivoted against said bias to an open valve position to permit cartridges to be fed
into the feed throat in a direction perpendicular to the housing axis.
8. A drum magazine as claimed in claim 7, characterised in that the pivotal lip (417)
has a tail portion (422) forming said preventing means which, when the magazine is
in a gun receiver, prevents the pivotal lip from rotating.
9. A drum magazine as claimed in claim 7 or 8, characterised in that the fixed lip
(418) is tapered in a direction to permit the nose of the cartridge to be directed
upwardly away from the feed throat (415).