Magazine status indicating devices

Sonic devices to indicate that no cartridges are present in a magazine, or that at least one cartridge is present.

Many firearms use detachable magazines which can be removed from the 
firearm when empty and replaced by full magazines. Some of these magazines 
have a large capacity so that during firing it is difficult for the user 
to remember how many cartridges remain in the magazine. Some firearms 
include devices which indicate to the user when the last shot has been 
expended, otherwise he might be holding an empty firearm and not be aware 
of the situation. Obviously, it would be an advantage if the user could be 
informed when he still has one shot available; thus he could exchange 
magazines while the firearm still has the capability to fire a shot. 
Of course, it should be understood that in most firearms having magazines, 
when only one shot remains it is in the barrel, and the magazine is empty. 
But some firearms ram the cartridge from the magazine only when it is to 
be fired. 
With either arrangement, if the user can be made aware that he has only one 
cartridge remaining in the firearm, he can either fire it, or retain it 
ready to fire while he exchange magazines. 
The principal object of this invention is to provide devices by which the 
user can determine whether or not a cartridge is present in a magazine.

The drawings are not to scale and are simplified for clarity of disclosure. 
No particular magazine is shown, as the invention can be applied to 
various magazines, including some which may differ in detail from those 
illustrated. 
FIG. 1 shows a portion of a magazine having side walls 1 and 3 and a 
moveable cartridge follower 5. Pivotably mounted on follower 5 by means of 
pin 7 is platform 9. The pin is affixed to the sides of the folower in any 
suitable manner. 
FIG. 2 shows the follower out of the magazine and also shows how a typical 
wire coil spring 11 can engage the follower to urge cartridges in the 
magazine toward the feed position in the usual manner. 
In FIG. 1 a cartridge 100 is resting on platform 9. Assuming that a spring 
such as 11 is thrusting the follower and the platform upward, cartridge 
100 will be pushed against feed lips 13 and 15 in the usual manner. When 
this condition occurs, platform 9 will be held firmly between the 
cartridge and the follower as may be seen also in FIG. 2. If the magazine 
should than be shaken, the follower will not rattle. 
The dimensions of the platform are so chosen that it can pass between lip 
13 and lip 15 as may be seen in FIG. 3. When no cartridge is in the 
magazine the platfrom can oscillate on the follower and impact it. This 
serves as a sonic indication that the magazine is empty. It may be 
desirable in some instances to so choose the axis of oscillation of the 
platform that the platform will be definitely unbalanced on the pin. This 
is indicated by arrows A and B in FIG. 2 which show that portions of the 
platform on each side of the axis differ in length. 
The unbalanced arrangement will assure that the platform will oscillate 
even if the magazine is shaken up and down, that is, along the vertical 
axis of FIGS. 1, 2, and 3. 
FIG. 4 shows a portion of a magazine having side walls 17 and 19 and a 
moveable cartridge follower 21. The top of the follower is slotted to 
provide a recess for mounting a roller 23, which can transmit the thrust 
of the follower to a cartridge 100 which is positioned between lip 25 and 
lip 27 at the top of the magazine. The use of such feed lips is well-known 
in the art and need not be further described here. 
Roller 23 is loosely mounted on a shaft 29 which is fixed in follower 21 as 
may be seen in FIG. 5. Also fixed in the follower is a thrust plate 31 
which is adapted to receivd the upward thrust of a typical wire coil 
spring 33. 
The effect of this arrangement is that when a cartridge is present, as in 
FIG. 4, spring thrust on the follower is transmitted via the roller to the 
cartridge. There is then no tendency for the roller to rattle when the 
magazine is shaken. When no cartridge is present, as in FIG. 6, the 
follower will contact the lips but the roller is free to rattle and thus 
signal that the magazine is empty. To increase the sonic effect, the 
roller can be made hollow. 
FIG. 7 shows a portion of a magazine having side walls 35 and 37 and a 
moveable cartridge follower 39. A recess 41 is formed in the top of the 
follower, it being best seen in FIG. 10. Below the recess a box 43 is 
affixed to the follower, it serving as a retainer for a ball 45 which 
protrudes slightly above the upper surface of the follower as may be noted 
in FIGS. 7, 8, and 9. The dimensions of the ball, the box, and the recess 
are so chosen that the ball can move somewhat in the box, but that such 
movement can be prevented by contact with a cartridge 100 which rests on 
the follower in FIG. 7 and FIG. 8. 
A typical wire coil spring 47 can be positioned to exert upward thrust on 
follower 39 in FIG. 8. When the follower is thrust upward, ball 45 is held 
between the follower and any cartridge which happens to be in the 
magazine. Such a cartridge would be pushed against lip 49 and lip 51 as 
may be seen in FIG. 7. When the ball is thus held, it will not rattle. 
When no cartridge is present, as in FIG. 9, the follower contacts lips 49 
and 51 but the ball is free to rattle as its diameter is less than the 
distance between the lips. The sound made by the ball as it rattles 
indicates that the magazine is empty. To accentuate the sound the ball can 
be hollow, or a resonance box can be positioned below retainer box 43. 
Such a resonance box is indicated by broken lines in FIG. 7 and FIG. 8 and 
is numbered 53. 
Retainer box 43 can be made elongated in one dimension as is best seen in 
FIG. 8. To increase the sonic effect as the ball strikes either end of the 
box, lugs such as 55 and 57 can be fixed within the box at each end, as 
can be seen in FIG. 10. Furthermore, a plurality of balls can be provided, 
if desired, to make a distinctive sound. 
There is thus disclosed several magazine status indicating devices which 
can be used to inform a user whether or not any cartridges are in a 
magazine. With any of these devices the user simply shakes the magazine 
and listens for a sonic signal. This may be done while the magazine is 
installed in a weapon, or while it is removed from the weapon. The 
disclosed devices may be employed with magazines for various classes of 
weapons. To increase the sound effect, the ball shown in FIGS. 7, 8, 9, 
and 10 could be made of a hard and dense material such as an alloy of 
tungsten.