US 2793590 A
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y 8, 1957 E. w. BRANDT 2,793,590
PRACTICE PROJEC'IILE Filed March 13, 1953 Fig.1
3 m 5 M EBA/VD r v INVENTOR sYgg m W ATTORNEYS PRACTICE PROJECTILE Edgar William Brandt, Geneva, Switzerland, assignor to Anstalt for die Entwicklung von Erfindungen und gewerblichen Anwendungen Energa, Vaduz, Liechtenstein, a corporation of Liechtenstein Application March 13, 1953, Serial No. 342,181
Claims priority, application Switzerland April 5, 1952 1 Claim. (Cl. 102-41) This invention relates to a practice projectile.
Certain types of projectiles are known which, on being fired from a gun barrel and stabilized byvanes, are given a slow gyration due to a slight inclination of the rifiing of the weapon, which is intended to prevent the systematic deviation to which they would be subject if there were no gyration, under the influence of an asymmetry of shape or unbalance of mass.
Practice projectiles of this type have the disadvantage of being expensive, since they are not recoverable and must nevertheless possess an empennage produced with the same care and the same precision as that of a corresponding operational projectile. Moreover, the empennage is often over-sized i. e. adapted to open out after leaving the gun.
One of the objects of the present invention is to produce an economical practice projectile which can be fired from the same weapon and under the same conditions as a vaned projectile of the aforementioned type, but stabilized by the slow gyration which, in the case of the operational projectile only had the function of increasing the accuracy of fire and was not intended to effect stabilization during the trajectory of the projectile.
The practice projectile of the present invention, which is intended to be fired from a gun having slightly inclined rifiing, is encased inside a case and comprises a hollow cylindrical body, a driving band, a conical ballistic cap deformable on impact, and a flat base of light material. Said projectile is characterized in that said hollow cylindrical body, which is of high density, has a height substantially equal to its diameter, the total height of the shell being smaller than two calibres.
Experience has shown that a cylindro-conical projectile complying with the foregoing requirements, that is to say relatively short in relation to its calibre, remains stable over the whole of the useful part of the trajectory, thus ensuring accurate firing despite its low mass density (total mass of the projectile divided by its section at the level of the midway section) and the slow gyration imparted thereto.
The hollow cylindrical body preferably constitutes nine tenths of the total mass of the projectile. Since the greater part of the weight of the projectile is distributed over its periphery, it follows that the projectile retains on its trajectory a gyroscopic energy sufiicient to ensure its stability. Moreover, as the conical ogive and the base do not by themselves amount to more than one tenth of the total weight, the longitudinal couple is minimal and a suitable distribution of the masses avoids the rocking of the projectile.
In order to increase the mass of the cylindrical body and to dispose the centre of gravity of the projectile in a position such as to impart optimum stability to the projectile during the course of the trajectory, it is desirable to make the rear part of said body thicker. According to one embodiment of the invention, the cylindrical body has, starting from mid-height and as far as the base,
' a thickness double that measured over its top part.
Patented May 28, 1957 According to one embodiment of the invention, the body of high density may comprise two parts, one acting as a framework and of lighter material than the second, and the'other being outside the first and constituting the principal mass of the body which forms a stabilizing centrifugal mass.
Another feature of the invention consists in the position of the driving band adapted to take the rifiing of the barrel, which is disposed forwards of the body, level with the base of the ballistic cap, so that the construction permits the engagement of the whole body of the to say, the ejection of the case after the shot has been projectile in the case, thereby ensuring good behaviour and protection of the whole arrangement.
. Although the dimensions and proportions of the hereindescribed practice projectile are essentially different from those of the corresponding operational projectile, care is taken to encase both of them in identical cases containing identical propulsive charges so as to obtain the same recoil effect on the gun for both types of ammunition and the semi-automatic operation of the breech, that is Thus, according to the invention, the volume of the combustion chamber contained inside the case of the practice projectile can be reduced by lining the same internally with a sheet of an inert material such as cardboard wrapped around itself.
The base of the projectile, of light material and slightly smaller in diameter than that of the body, is able to fit into the latter and to adhere there as a tight fit. It can, moreover, carry on its inside face a tracer charge and a self-destruction charge.
By virtue of the aforedescribed structural arrangements, the projectile of the present invention facilitates practice firing, renders it economical and free from danger. The tracer ensures visibility of the trajectory and the self-destruction charge prevents ricochets.
In fact, during operation a double break-up takes place, the body of the projectile becoming separated from its base and from its ballistic cap.
On impact with the ground, the deformable ogive of light metal, or if desired of plastic material, is shattered and the cylindrical body bites into the ground by which it is immediately checked.
In order to enable the invention to be more readily understood, reference is made to the accompanying drawings, which illustrate diagrammatically and by way of example, two embodiments thereof and in which:
Figure 1 is a side elevation in partial longitudinal section of an operational hollow charge projectile in its case;
Figure 2 shows a side elevation of a practice projectile according to the invention, in longitudinal half-section;
Figure 3 shows a side elevation partly in longitudinal section of a modified form of the projectile illustrated in Figure 2;
Figure 4 shows diagrammatically the dismemberment by self-destruction of the projectile shown in Figure 2 and Figure 5 shows diagrammatically the projectile illustrated in Figure 2 on impact with the ground.
The operational and practice projectiles illustrated respectively in Figures 1 and 2 are of the same weight and the same calibre, are fired with the same charge of powder and are subjected to the same pressure on the firing of the shot, so that they receive the same initial velocity.
The practice projectile illustrated in Figure 2 and forming the subject of the invention comprises a hollow erably consists ofsteel, castiron'or brass, while an aluminium alloy can be used to make the ogive 2 and'the base 3. The centre of gravity G of the projectile is situated about one quarter of the total height of the projectile from the base, because ofthe substantially 'doubledthickness of the body 1 over the rear half ofits-height.
The driving band 7 is placed near-the frontend'o f thebody at the base of the ballistic cap 2.,and is -preferably,
after the style of theballistic cap of the operational-.pro--. jectile, constituted by a simple metal wire embedded a peripheral groove 7a in the body 1.
Theapracticeprojectile is'encased in a-case Sidentical With.that of the operational projectile, comprising at its base a i propulsive.- cartridge 9 housed in= a'perforated jacket 10 sandisurrounded externally bysmall b'ags of powder 11. Finally,-a sheet of cardboardlZ- placedin the case 8 enables the free-inside volume of the case to be varied dependingon its dimensions, in ordentocompensate-nfor the differences oflthe-dirnensions -of.sthe praetice projectile and the operational projectile.
Accordingtto. Figure 1, the latter-is bi-ogival and stabilized on. its trajectory by an empennage, the ;vanes "13 of which are unfolded on leaving the muzzle ofithe gun.-
Therpracticerprojectile. of the. present invention --is sta=- bilizedpas a result of its proportions, by'theslow gyration 4 imparted to it by the slightly inclined rifling of the gun.
Thus an-inclination of the rifiing by only one degree in relation to the axis of the barrel is sufficient to ensure the stability of a projectile of this type, with acalibre'of 90 millimetres, receiving an initial velocity of 600 metres per second and weighing about 2 kilogrammes.
As a modifieation, the metal cap 2 may be replaced by a light ballistic cap of plastic material as shown at 2a (Figure 3).
What I claim is:
A-practice projectile for firing'in a gun having a slightly' References Cited inthe file of this patent UNITED STATES PATENTS 1,292,388 Bowers Jan.'21, 1919 2,246,429 Brandt June 17, 1941 FOREIGN PATENTS;
19,481 Great Britain of 1890