US2446082A - Incendiary projectile - Google Patents

Description

July 27, 1948. c. A. DIXON INCENDIARY PROJECTILE Filed Nov. 24, 1942 due a lWVf/WUP BY [0 d flail Jam,

' HTTOP/VH Patented July 27, 1948 UNITED STATES ENT OFFICE INCENDIARY PROJECTILE Application November 24, 1942, Serial No. 466,803 In Great Britain September 15, 1941 Section 1, Public Law 690, August 8, 1946 Patent expires September 15, 1961 2 Claims.

This invention relates to incendiary projectiles, and is concerned with projectiles of relatively small calibre, such as are used in machine guns, in which the space available for the incendiary filling is restricted, and it is not practicable to use a normal direct action and or time fuze, such as can be employed in shells of the larger calibres.

The main object of the present invention is to provide an improved construction of incendiary bullet which, for its calibre, has a large capacity for incendiary material, is safe to handle and to fire even from a hot gun barrel which is badly worn, and is simple to manufacture and fill by mass production methods.

The improved incendiary bullet according to this invention, comprises an outer envelope containing a tubular sleeve of steel having its bore filled with an incendiary mixture. The incendiary mixture is preferably one capable of being ignited by distortion of the nose of the envelope on impact without the use of a detonating or other auxiliary material. A thin packing sleeve of a lead alloy, or other soft metal, may be interposed between the envelope and the steel sleeve.

In the preferred construction the rear end of the steel sleeve is closed in such a way as substantially to prevent base ejection of the incendiary filling. Thus the rear end of the sleeve may be internally screw-threaded .to receive a screw-threaded closing plug, preferably retained firmly in position by the use of a suitable cement. Alternatively the rear end of the bore of the sleeve is closed by a soft metal plug, held in position by means of a rigid disc, for example of steel, pressed against the end of the sleeve. The disc may in turn be secured by means of an outer soft metal plug over the rear end of which the skirt of the envelope may be pressed by a spinning or other suitable operation.

The ignition of the incendiary filling on impact may be efiected by a hard metal element or anvil disposed in the nose of the envelope so as to co-operate with a steel ball or other hard metal element embedded in the filling. In an alternative and preferred arrangement, the envelope has a tapered nose extending beyond the front end of the sleeve and the space within this nose is filled with the incendiary mixture, 2. part of the wall of the nose (where it is not supported by the sleeve) being weakened by reducing its thickness, in order to facilitate distortion of the envelope and consequent ignition on impact.

Two convenient constructions of incendiary bullet and a suitable incendiary filling for such bullets, will now be described by way of example,

with reference to Figs. 1 and 2 of the accompanying drawings.

Figure 1 shows one embodiment of the invention in longitudinal section; and Figure 2 shows another embodiment of the invention in longitudinal section.

In these bullets, the filling is of such a nature that it can be ignited by the impact of the bullet without the use of a separate charge of detonating material which, in known forms of bullet. is usually disposed in the nose of the bullet and has embedded in it a steel ball or other solid body acting, on impact of the bullet, to cause detonation of the charge which in turn acts, either directly or indirectly, to ignite the incendiary filling. The filling comprises a. mixture of a combustible metallic material, such as a readily oxidisable metal, metal alloy, or oxygen-free metal compound and a compound containing oxygen available for the combustion of the combustible material. Thus the mixture may consist of a powder of a magnesium-aluminium alloy, and a non-hygroscopic nitrate, preferably barium nitrate. A preferred mixture comprises approximately 50% of powdered magnesium-aluminium alloy (containing between 47% and 53% magnesium and between 53% and 47% aluminium), and approximately 50% of dry barium nitrate.

The two specific constructions of incendiary bullet now to be described are primarily intended for machine guns of so called small arms calibre, that is of a calibre of .303" in the case of British Service weapons, or of the corresponding calibre used by other countries, but it will be readily appreciated that incendiary bullets of other calibres can be similarly constructed.

In the first construction shown in Fig. 1, the bullet has an outer envelope I of thin (for example 0.025-0.1'7 inch) copper and zinc alloy, such as so-called gilding metal, containing about copper and 10% zinc. Inside the envelope is a sleeve 2 of steel having a central bore with (in the case of an .303" bullet), a diameter slightly less than half the calibre of the bullet. The steel sleeve is separated from the envelope by a thin packing sleeve 3 of a soft metal, such as a lead-antimony alloy and of a few hundredths of an inch in thickness. The envelope, which is preferably formed by a series of pressing operations from a cup shaped blank, tapers to the nose 4, the taper preferably being such that about half the total length of the finished bullet is tapered. The length of the steel and soft-metal sleeves may be such that when they are inserted in the envelope, their forward ends extend only about half way along the interior of the tapered portion of the envelope.

Wedged in the nose of the envelope is a more or less conical plug 5 of hard metal, such as steel, having a substantially fiat rear surface, which, on impact cooperates with a ball 6 of steel or other hard material embedded in the incendiary material I packed tightly in the remaining space in the nose and in the bore of the steel sleeve.

When the incendiary filling has been packed in the rear end of the sleeve, it is closed by a plug which cannot easily be displaced, the object of this closing plug being to ensure that during combustion, the filling burns from the forward end of the bullet and the continuity of burning is not decreased by the ejection of the whole or a part of the filling from the rear end of the sleeve. Accordingly the rear end of the steel sleeve may be internally screw-threaded to receive a screwthreaded plug 8 which is preferably fixed firmly in position by the application of a suitable cement to the under surface of the head of the plug before it is screwed in. In a preferred arrangement, shown in Fig. 2, the bore of the sleeve is closed, after filling nearly to the end, by a soft metal plug 9 formed by pressing a ball of leadantimony alloy, or other soft metal, into the sleeve by means of a steel disc I0 which has a diameter slightly less than the internal diameter of the envelope. The soft metal ball is of such a size as to project beyond the end of the sleeve and be deformed to fill such end when it is pressed in as the steel disc is forced into contact with the rear of the sleeve. The steel disc is held in place by an outer plug H of antimonylead alloy, or other soft metal, which fits into the end of theenvelope and is, in turn, held in place by turning inwardly the skirt l2 of the envelope (which is of such a length as initially to project rearwardly of the end of the sleeve), so as to form an inwardly projecting flange firmly pressed on to the rear surface of the lead disc. Preferably the final pressing operation, in which the lead disc [I is secured by the skirt of the envelope, is such that the rear of the finished bullet is slightly tapered, i. e. so that the complete bullet becomes boat-shaped in cross section, in order that the ballistics of the bullet may be substantially matched with those of a solid bullet notwithstanding the fact that the incendiary bullet is somewhat lighter due to its incendiary filling.

The second construction, shown in Fig. 2, also differs from the first in that ignition of the incendiary filling is effected solely by the collapse of the nose of the envelope on impact Without the use of an anvil and co-operating ball, or the equivalent, within the nose of the envelope. In order, however, to ensure that there will be sufficient percussive action to cause ignition of the filling when the bullet strikes its target, the wall of the envelope between the nose and the forward end of the sleeve is weakened slightly at I3 so that it will readily crush, this weakening not, however, being sufficient for the bullet to be distorted by the set back forces occurring during firing. Thus a drill may be inserted in the end of the envelope so as to produce on the inside of the wall near the nose, a narrow annular groove. This method has, however, the disadvantage that owing to difficulties in centreing, the groove may not be symmetrical with the result that part of the wall may be too thin to withstand the set back forces. Accordingly the desired weakening of the wall just behind the nose 4 of the bullet at [3 is preferably effected by the use of suitable punches and dies during the pressing out of the envelope. With this construction of bullet, the sudden crushing in' of the nose on impact will produce adequate percussive forces to cause ignition of the incendiary filling which is closely packed within the whole of the available space. In other respects this construction is similar to the first construction and accordingly need not be described in further detail.

The use in the improved bullets according to the invention, of a steel sleeve within the envelope has the advantage that it strengthens the bullet as a Whole and thus ensures that it will withstand the stresses to which it is subjected during firing. In addition this sleeve provides thermal insulation of the incendiary material so that the bullet can safely be fired from a hot un barrel or one in a badly worn condition Without the risk of premature ignition. A further advantage of the sleeve is that owing to its high degree of rigidity it does not readilydeform on impact and thus the continuity of the column of incendiary material in the bore of the. sleeve is maintained, and. this material is accordingly used in its most efiicient manner. The intermediate lead sleeve allows the envelope to yield under the pressure of the rifling during firing and thus lessens the wear on and the heating of the barrel which would otherwise occur.

These improved bullets also have the advantage that by the use of an incendiary filling which is capable of being directly ignited without an auxiliary detonating charge, not only is the space available for the incendiary material greater than that in the known bullets referred to above, and thus the effectiveness of the bullet increased, but also, by the omission of the detonating charge, the sensitivity of the bullet is reduced to an extent sufficient to avoid premature ignition in a hot gun or ignition before adequate penetration of the target (such as the petrol tank of an aircraft), withoutloss of performance of the bullet.

It is to be understood that the above description is by way of example only and that various'modifications may be made within the scope of the invention.

I claim as my invention:

1. An incendiary projectile comprising an outer envelope, a steel sleeve within said envelope, a packing sleeve of soft metal between said steel sleeve and envelope, a tapered nose and a rear portion for said envelope extending beyond the front and rear ends respectively of said steel sleeve, a portion of the wall of said nosebeing of reduced thickness to facilitate distortion on impact, an incendiary filling within said sleeve and nose, said filling being capable of being ignited by the distortion of said nose on impact, a soft metal plug extending into the rear end of said sleeve, an outer plug embraced by the rear portion of said envelope, and a hard metal disc between and in close contact with the two plugs.

2. An incendiary projectile comprising an outer envelope, a steel sleeve within said envelope, a packin sleeve of soft metal between said steel sleeve and envelope, a tapered nose and a rear portion for said envelope extending beyondthe front and rear ends respectively of said steel sleeve, a portion of the wall of said nose being of reduced thickness to facilitate distortion on impact, incendiary material filling said sleeve and nose, said material being one which will be ignited by the distortion of said nose on impact, and

5 closing means embraced by the rear portion of Number said envelope and extending into the rear end 1,300,195 of said sleeve. 1,380,773 CECIL AUBREY DIXON. 1,494,718 5 1,875,985 REFERENCES CITED 2,033,966 The following references are of record in the 2,217,645 file of this patent: 2,288,627 UNITED STATES PATENTS l0 2323303 Number Name Date 1,101,743 Hoagland June 30, 1914 Number 1,181,278 Wiley May 2, 1916 316,785

Name Date Rockwell Apr. 8, 1919 Clay June 7, 1921 Semple May 20, 1924 Brandt Sept. 6, 1932 Wiley Mar. 17, 1936 DeWilde, et a1 Oct. 8, 1940 Ko'walski July 7, 1942 Bluehdorn, et a1. July 6, 1943 FOREIGN PATENTS Country Date Italy Apr. 14, 1934

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