US2172054A - Projectile having its center of gravity in front of the center of resistance - Google Patents

Description

Sept. 5, 1939. A. 0| BRAZZA-SAVORGNAN PROJECTILE HAV ING ITS CENTER OF GRAVITY IN FRONT OF THE CENTER OF RESISTANCE Filed July 15, 1956 Patented Sept. 5, 1939 UNITED STATES PROJECTILE HAVING ITS CENTER OF GRAVITY IN FRONT OF THE CENTER OF RESISTANCE Ascanio di Brazza-Savorgnan, Rome. Italy Application July 15, 1936, Serial No. 90,632.

In Italy July 18, 1935' 2 Claims.

The object of the present invention is to provide a projectile which does not tend to turn over during its trajectory (and therefore shoots accurately) evenif shot from smooth bore firearms.

Until now, it has been attempted to attain this object by applying to projectiles shot from firearms, the prehistorical principle of the arrow, javelin, etc.

In these, the stabilizing action of the air, acts on the tall or rear portion of the projectile, but it is evident that it ceases to fulfil its functions when the velocity of the projectile during its trajectory, is high enough as to produce a vacuum (or something practically equivalent) around the said rear part of the projectile.

This rear part is then deprived of the support of the surrounding air, and nothing prevents the projectile from behaving as any missile starting its'travel through the air, with its center of gravity in a rearward position with respect to its center of resistance, without being provided with stabilizing means, as for. instance with rotation imparted by rifled gun barrels.

As the head or fore portion of the projectile is hampered in its forward motion by the cushion of compressed air which it drives in front of itself during its flight, a projectile having its center of gravity inthe position above mentioned, and not having any rotary movement round its axis, will rest on said cushion of compressed air, will be in a condition of unstable equilibrium and will consequently have a tendency to overturn.

In both cases anyhow, the accuracy of the shot is lost. I This happens already with much lower velocities of flight of the projectile, than the velocities obtained with a common shotgun, using a single bullet and a normal propelling charge.

The named principle of the arrow, etc., applied to projectiles destined to be shot from firearms, is therefore only eflicient,if these projectiles possess very low velocities of flight, as for instance the bombs shot from smooth bore mortars, with very small propelling charges.

tioned projectiles, however, owing to their low velocity of flight, possess only. a relatively short range, and if their. velocity is augmented by increasing the propelling charge, their range might increase, but the accuracy of the shot is lost.

One of the objects of the present invention, besides its application to sporting guns, is also to provide for military purposes, a projectile for smooth bore mortars, capable of flying without turning over, even if shot with a very high muz- These last men-- zle velocity; and possessing therefore a very long range of accurate shooting.

The present invention is based on the following principles.

(1) To obtain the stability of projectiles of cer- 5 tain shapes, during their flight, by the pressure of the air on their anterior portion, orhead or nose as it may be called. I

(2) To determine-the position of their center of resistance, i. e., the resultant of the resistances 1 opposed by the air to-the motion of the projectiles along their whole trajectory.

(3) To give to these projectiles such shapes, proportions and composition, that their center of gravity is placed, during their whole trajectory, in front of their center of resistance.

The accompanying; drawing shows schematically and by way of example some forms of real- 'ization of the object of the invention, in which:

Figure 1 shows a projectile of spherical shape, 20

in which a segment of its rear portion has been out off.

Figure 2 shows a projectile having a semispherical head and a cylindrical rear portion.

Figures 3 and 4 show projectiles having a more elongated cylindrical rear portion, with heads formed as spherical segments of different height and curvature.

Figures 5, 6, 7 and 8 show projectiles in flight along their trajectories and the rear limit of their 30 compression wave.

Figures 9, 10 and 11 show three forms of removable rings, provided with one or moreslots, for setting of "the projectile in its cartridge.

Figure 12 shows in section thefore part of a shot gun cartridge, with a projectile on which a trimming ring' is superposed as that shown, in

" Figures 9, 10 and 11.

The stability of a pro ectile obtained through the pressure of the air on its head instead of the stability obtained by-the action of the ar on its tail, has the obvious advantage that the former is a factor which, instead of failing, is more than ever efiicient, even at the highest velocities of flight of the projectile. 45

As to the center of resistance, applicant started from the supposition that, in a projectile with its head shaped as'a semisphere or as a spherical segment of suflicient curvature and height, this center of resistance corresponds almost exactly, and in any case with very great approximation, to the center of curvature of the semisphere or of the spherical segment.

As to the center of gravity of a projectile having its anterior part shaped as described, if one is not bound by any particular weight or length to be given to the same projectile, it is an easy matter to make it coincide with a point of the longitudinal axis of the said projectile, fixing surface, for instance on a mirror, resting on its rounded head. 7 r

If in this position the projectile can oscillate without falling down, it answers the purpose, but if it falls to one side, it does not answer the purpose. I

The correctness of the supposition concerning the correspondence of the before named center of curvature with the center of air resistance, was confirmed by experience as, after many causes of disturbance had been eliminated, it resulted that none of the projectiles which could oscillate in the named manner on a mirror, would turn over during its flight, at a distance of 100 metres (nearly 110 yards) at which distance experiments were chiefly made, whereas if they overturned on a mirror or similar flat surface, they struck the target more or less sideways.

In said experiments, the muzzlevelocities measured at an oflicial experimentingstation,were of around 385 meters (1262 feet) per second with a 12 gauge projectile weighing 33 grammes (nearly 510 grains) and shot from a full choke Browning shotgun. I

The highest velocity triedrwas up to 741.9 metres (2432 feet) per second, with a little bullet of the diameter of 7.2 millimetres, weighing 2.05

rammes (a little over 30 grains) and shot from a military carbine, the rifling of which had been taken away.

Also bullets as heavy as 730 grains, were shot from a 12 gauge shotgun.

Of the latter, the velocity was not measured but they all struck the'target in head-on position.

The great diflerence in weight and size, and

. also (within certain limits) 'of shape of the proiectiles tried at very different velocities, some of which as high as those stated, undoubtedly confirm the correctness of the supposition of the inventor, concerning the correspondence of the center of curvature of the head, with the center of air resistance, in projectiles having the head of theshap'e abovev described. i

The exper'ments have also shown, within the limits of volocities tried, that this correspondence does not practically change, with the change of velocity, and also evidently does not change with respect to the oscillations of the projectile, along its trajectory, 'to which every projectile is more or less subjected during its flight.

To come to the shapes to be given to projectiles, in order that they should realize the object of the present invention, these shapes do notdifl'er from those already known, but the novelty consists in finding the exact measures and proportions which must be given to the same.

A shape answering theoretically the aforesaid conditiomwould also be the one shown on Figure and grooves.

According to applicant, there still remained two all dimensions 1, which simply represents a sphere in which a segment of what would have been its rear portion, has been cut away.

In practice however, this shape has not been found advisable as compared with other shapes hereinafter described.

Another shape would be like the one shown on Fig. 2, which represents a projectile having a fore part of head I shaped as a half sphere, and a rear part 3 shaped as a cylinder having the same radius as the sphere, and such height so that its volume (and weight) is equal to that of the fore half sphere.

Such height may be easily calculated, and results to be two thirds of the radius of the sphere.

The whole projectile has thus the same volume and weight, as a spherical one having the same diameter. I

Also the position of the center of gravity of a projectile of such a shape, is easily calculated, and is situated above the center of curvature of the semispherical part, at a distance equal to A of the radius of the same. This might seem little, but experience has shown it to be sufilcient in practice. Said distance is certainly not excessive and cannot therefore be substantially diminished. It shows besides, that a slight imperfection or deformation of the form, or a little alteration of its proportions is suflicient to produce an inaccurately shooting projectile, instead of a very accurately shooting one.

In Figures 1 to 4 the distance between the center of gravity b; and'the center of curvature c has been exaggerated for the purpose of showing these two points separately.

If projectiles of the design above mentioned weredestined to be used with smooth cylinder bore barrels, they could be made exactly as shown in Figure 2, and having such diameter as to fit exactly the bore of the gun,- in respect to which bore they would then possess a sufficient weight. If, however, they were to be used with choke bore barrels (as almost all actual shotgun barrels are) their diameter would have to be reduced so as to enable thm to pass easily through the narrowest choke type of barrels.

In this condition (as it has been confirmed by experience) their accuracy could only be satisfactory, if their cylindrical part be provided, with some of the known devices (used since the early years of "this century) to guide a slug truly through the bore of a choked barrel.

As it is known, these consist of a longitudinal, oblique or annular ribs and grooves.

Experience has also shown that there is no difference in the accuracy of shooting of projectiles provided with these diiferent kinds of ribs defects to a projectile of this shape and size, with reduced in proportion to its reduced diameter.

One consisted in the insuillcient weight (about one ounce for 12 gauge) which is considered too little not only by applicant but generally in Europe, for projectiles"of that kind.

The other defect (although in practical experience, it gave no trouble with, carefully loaded shells and suitable powder) was that. the cylindrical part (or to be more exact, substantially cylindrical as the named devices had somewhat modifled it) was very low, so that in passing from the shell to the bore of the barrel, the bullet might not have been guided enough, to be pre- 75' vented from entering the oblique position. v

Lengthening the cylindrical part, without displacing rearwards the center of gravity, meant lightening that part (through cavities or through the use of lighter materials) and therefore the whole bullet, already considered too light by applicant. vTo get a heavier bullet of the same diameter and with a longer cylindrical part, and maintaining the required relationship between center of curvature and center oi gravity, the radius of what-had been the semispherical part, was augmented.

This part got thus the shape oi a spherical segment 2 as shown on Fig. 3 which shows that all the desired requisites were fully maintained. In Fig.4 these characteristics are augmented.

As already said, applicant experimented with success bullets as heavy as 730 grains, in a 12 gauge shotgun.- He himself does not consider this weight advisable as a rule, but he made this experiment to show that the so-called, Paradox or ball and shot guns, which shoot bullets of this weight, are by no means superior to an ordinary shotgun, loaded with a bullet, made according to his invention.

There is evidently a limit in increasing the radius of the spherical segment forming the head of the bullet,- and the consequent flattening of the same. In fact, for the projectiles of the shapes described, it is evidently advisable that, even with the maximum oscillations that the projectile may be subjected to, during its flight, the rear limit of the compression wave 1n=1t (Figures 5, 6, 7 and 8) must not arrive to touch (Figures 5, 6) or at the maximum may reach the base of the spherical segment (Figure 7). It the condition shown in Flgure8 should be realizeed, the oscillations of the projectile would probably cause the line m=1r to be modified, i. e., the support of the projectile itself, and this would probably cause its upturning. The limit to which the radius of the spherical segment can be augmented, and consequently its curvature and its height can be reduced, without endangersame, in a somewhat ing the stability oi the projectile, is evidently a function of its velocity and this limit may be determined by experiment.

In loading game shooting cartridges, applicant has found it advantageous to provide the projectile with an annular wad I (Figures 9, 10, 11 and 12) of suitable thickness, cut in a point (Figure 9) or preferably in two or more points at even distances (Figures 10 and, 11).

This allows the bullet to be well protected within the shell, and not giving trouble by projecting out of the same, if used with repeating or self loading guns.

This allows also to give to the cartridge a good turnover and a correct-opening at the moment of the shot, which might otherwise cause some trouble, owing to the convex shape of the head of the projectile. This is shown in Figure 12, in which 4 is the annular wad cut in t, p is the projectile, s is the usual wad, interposed between the charge 0! powder and the projectile, and o is the cartridge edge turned over.

As the said annular wad is cut in a point or, divided in several parts as above mentioned, the

of gravity ofthe whole projectile is disposed in front of the center of curvature of said forward part.

2. Projectile according to claim 1, in combination with a cut annular wad, adapted to be superposed upon the projectile in the cartridge, so, that the turn over of the latter is caused to rest on the face of said out wad, in order to hold 2 it in place.

ASCANIO n1 BRAZZA-SAVQRGNAN.

Images