Drum-magazine for firearms.

Application filed July 13, 1909. Serial No. 507,402.

To dll whom it may concern:

Be it known that I, Karl Krnka, engineer, a subject of the Emperor of AustriaHungary, residing at Hirtenberg, in the 5 Province of Lower Austria, Empire of Austria-Hungary, have invented certain new and useful Improvements in Drum-Magazines for Firearms; and I do hereby declare the following to be a full, clear, and exact 10 description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

In drum magazines, as is evident from the nature of the case, the feeding of the 15 cartridges into the receiver of the breech casing usually takes place somewhat from one side, so that the. uppermost cartridge, ready for conveying into the receiver, does not lie immediately below the produced cen20 ter line of the barrel, and must therefore be advanced in an oblique direction. . In the case of ordinary magazine rifles this is no disadvantage, in automatic firearms however, where the operation of loading is ef25 fected very rapidly, this circumstance can give rise to trouble.

The delivery opening of the drum magazine into the receiver was hitherto arranged somewhat on one side for the purpose of 30 allowing the magazine to be charged from packets by means of a cartridge frame inserted vertically into the weapon, as in the case of pressure directed against the longitudinal axis of the cartridge feeder the 35 latter would not be able to. rotate and a tangential motion from the side of the column of cartridges is therefore needed. The drum magazine under consideration however, effects an exactly central supply of 40 cartridges, although retaining the method of charging described above. At the same time it renders possible, which is most important, such a local disposal of the cartridges, that their bullet ends can rest di45 rectly behind the barrel without requiring an intermediate inclined surface between the barrel and the receiver. The. locking grooves in the casing for the locking lugs, are not placed as is customary between the 50 magazine and the barrel, but in the side walls of the breech, wherefore new conditions are given to this drum magazine to comply with modern requirements. For example the inclined position. of. the upper55 most cartridge necessary for its introduction into the receiver, is attained in a novel man ner for drum magazines. It is further proposed to arrange the whole magazine centrally in such a way as to remain unnoticeable from the exterior, without making this 60 part of the stock any wider than is usual. By avoiding the cutting through of the stock, the latter can besides be left stronger, whereby warping is effectually prevented.

This magazine does not require a special 65 method of taking to pieces, either by drawing or lifting out for example as it does not demand more frequent examination than for instance a trigger plate. The whole drum structure consists only of three parts made 70 sufficiently strong, the drum, the cartridge feeder and the feeder spring.

Figure 1 shows a partial section and side elevation of the rifle in the condition previous to the charging of the magazine. Fig. 75 2 is a transverse section of the preceding view, along the line I—II of Fig. 1, with the magazine empty. Fig. 3 the same section when the magazine is full. Fig. 4 shows a section along the line III—IV of 80 Fig. 1, looking to the right, and illustrates the assembling of the magazine. Fig. 5 a transverse section through the breech casing, With the magazine drum removed. Figs. 6 and 7 show the two faces of the 85 drum. Figs. 8, 9 and 10 show a side view and the two end faces of the cartridge, feeder. Fig. 11 shows the method of inclining the uppermost cartridge during its introduction into the barrel, and Fig. 12 is a. detail view 90 showing the ejector.

It may be clearly seen from Fig. 3 that the uppermost cartridge lies exactly in the center under the axis of the barrel and is located in its position by a peculiarly con- 95 structed rigid side rest 19, corresponding to the shape of the cartridge along its whole length. In Fig. 4 can also be seen the stepped part of this side rest 19, rendered necessary by the taper and the neck of the 100 cartridge case. A vertical upward movement of the uppermost cartridge is prevented by the cartridge holder p, shown in elevation in Fig. 1, and in section in Figs. 2 and 3. Fig. 3 shows that the cartridges are 105 pushed forward into the slot 20 by a rotary movement of the cartridge feeder t in the drum s, and rise until the uppermost cartridge engages the above mentioned side rest 19. This accurately formed rigid side 110 rest 19, is obtained by boring a hole 9 (Fig. 5) beginning at the rear face of the receiver

1,008,162 k, passing through the whole receiver underneath the middle bore and continuing in a tapered form corresponding to the shape of the cartridge. The necessary communig cation between this hole 9 and the drum s is established by means of the slot 20, stepped and tapered in a similar manner (Figs. 2,. 3 and 5). As the internal diameter of this slot 20 corresponds exactly to the 10 shape of the cartridge, the uppermost cartridge will also attain the necessary inclined position for its introduction into the barrel although the bullet end is not guided at all; the cartridge must however be lifted sharply 15 and rapidly as the bullet end lies close below the barrel. Fig. 11 shows, by means of a side view and two sections V—VI and VII—VIII, the produced inclined position of the axis of the cartridge. The dotted 2o double line 19—19 in the direction of the cartridge represents the rigid side rest described above, which is also shown in the sections V—VI and V1I—VIII. As the slot is wider at the first mentioned section 25 than at the second by means of the short advancing movement 21, the axis of the cartridge will be lifted through the height 23 at VII—VIII which, transferred to the side view at the same point, gives the bullet end 30 a lift of height 23, whereby the cartridge can easily reach the receiver. At the commencement of the above advancing movement the.rear end of the cartridge is kept low by means of the cartridge holder p 35 (Fig. 1).

It will be seen from Figs. 1, 2 and 3 that the drum s· as well as the cartridge feeder is entirely inclosed in the stock. The drum s is made to slide drawer-wise in the receiver 40 k by means of the two flanges 24 (Figs. 1, 6 and 7) on the drum and the two grooves 23 (Figs..4 and 5) in the receiver k which engage in each other. These flanges and grooves are stopped short in such a way 45 that the. drum can be pushed into its correct position on the receiver k from right to. left but cannot be pushed through. In this position it is held fast by the feeder spring w, which tends to push the drum s 50 through to the left. This spring w receives its required tension in sliding the drum into position as will be hereinafter seen.

The cartridge feeder t (Fig. 8) has a 55 long projecting rib 26 in addition to several short ribs for feeding the cartridges. The pivots 27 and 28 turned on the cartridge feeder, serving as its axis rest in the slotted bearings 29 and 30 on the drum s (Figs. 6 60 and 7) and are retained therein by the receiver as may be seen from Fig. 1, so that they can rotate only. In milling the bearing. surface for the feeder spring w the pivot 28 is formed at the same time, or else such 65 a pivot 28 can be permanently attached to the bearing for the spring, so that the cartridge feeder consists of a single rigid part. The feeder spring w has its two ends bent, one of which is inserted in the small drilled hole 31 in the feeder, and the other in the ₇₀slot 32 of the drum (Figs. 1, 7 and 10). These, two ends of the spring w, lie radially opposite each other in its free untwisted position, in Fig. 1 this in not shown to be the case, as the spring there possesses its initial ₇₅twist of 180°. The feeder spring w, is first placed on its bearing in the cartridge feeder in such a way that one end of the spring rests in the drilled hole 31. The cartridge feeder together with its spring is then in- ₈₀serted into the drum with the long rib 26 pointing downward, whereby the bent front end of the spring w, falls by itself into the small slot 32. By means of the long rib 26, the cartridge feeder which is already placed 85 in its bearings is then turned outward through 180° in the direction of coiling the spring, (i. e. from below to the right). The drum is then slipped into the receiver k (as shown in Fig. 4) the long rib being tilted 90 still farther in the direction of coiling, this being repeated in the case of the following short rib 33, in order that the latter can pass the first impeding Avail of the receiver. As soon as this has been carried out and in con- 95 sequence of the twisting of the spring, the drum will slide, by itself into its final position (Fig. 2) since the spring will tend to untwist further. In order to take them apart, the drum need simply be pushed ιοθ out to the right while overcoming the force of the spring.

The shoulders 34 and 35 (Figs. 1 and 2) serve to guide the cartridges from the U shaped drum s, to the slot 20 whose left- 105 hand lateral surface is tangential to the internal periphery of the drum. The latter is in the form of a semicircle with the exception of the above shoulders 34 and· 35.

It is of particular value in the case of no automatic firearms that the weapon after discharging the last cartridge, should automatically set itself ready for charging, for which purpose the feeder ordinarily moves into the path of the breech bolt. In the case 115 under consideration, the long rib 26 (Fig. 1) can not perform this duty, because neither the path of the head a, of the breech closing piece, nor that of the breech bolt δ or its locking lugs (Figs. 1 and 5) can touch the 120 magazine chamber since the special connecting passage 20 is located between the drum and the receiver. The long rib 26 can never reach up high enough, as its height is determined by the internal radius of the drum. 125 For this reason a rod h (Fig. 12) is used in the case of this drum magazine, and can be seen in Figs. 1 and 5. This rod also serves as a cartridge ejector for the breech bolt δ, but in the case under notice it is constructed 130

1,008,162 in such a way, as shown by Fig. 1, that it strikes the long rib 26 when the magazine is empty. It is dragged to and fro by the breech bolt which engages with the tooth 10 on the said rod (Fig. 12) and is shaped to correspond to the bored hole 9 (Fig. 5) in order that it cannot drop into the slot 20 (Figs. 2, 3 and 11). For drum magazines this rod h therefore represents a new means 10 for a known end, serving not only the ordinary function of an ejector but also as a stop for the breech bolt.