GB1591226A - Ballistic projectile - Google Patents

Abstract

The projectile is intended in particular for implanting a medicament in the body or the flesh of an animal, for example a cow, and consists of an elongated body (12) having a conical nose (14) at the front, with a slightly rounded tip (18). In its interior, it contains a central coaxial cavity (20) for accommodating the medicament. In order to achieve a small perforation, which protects the skin and the flesh of the animal, the conical nose (14) has an apex angle of 45-75 DEG , and the tip of the cone is rounded with a radius of 0.04-0.05 cm. In order to achieve good stability in flight, the projectile is provided at the rear with a recess (29). The projectile, having a diameter of 0.45 and 0.76 cm, can also be formed as an integral body from biologically active material. <IMAGE>

Description

(54) BALLASTIC PROJECTILE (71) We, MINNESOTA MINING AND MANUFACTURING COMPANY, a corporation organized and existing under the laws of the State of Delaware, United States of America, of 3M Center, Saint Paul, Minnesota 55101, United States of America, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: The present invention relates to sub-sonic ballistic projectiles having a unique combination of body shape and apparent density.

Due to their physical and ballistic characteristics and projectiles are particularly suited for the ballistic impact on and/or implantation in living animal bodies.

The art is replete with projectiles or bullets designed to be fired into animals with a view to disabling or killing the animal. Typically such projectiles have a high average density of about 10 grams per cubic centimeter, and are designed for deep penetration of animal flesh and for engendering great shock which causes maximum trauma to the animal.

Ballistically implantable projectiles containing biologically active materials for implantation into living animal bodies have been disclosed in U.S. Patent 3,948,263 issued April 6, 1976, and U.S. Patent 3,982,536 issued September 28, 1976.

These projectiles inherently have a low apparent density and provide the capability of obtaining precisely controlled ballistic implantation within a target, such as an animal body. However, the low density materials used in these ballistic projectiles can cause fouling problems when shot through conventional land and groove barrels.

According to the present invention there is provided a projectile having an elongate body portion for close fitting engagement with the inner surface of a barrel from which the projectile is to be propelled (e.g. the barrel of a compressed gas powered device) and a nose portion coaxial with and tapering generally conically from one end of the body portion at an included angle of greater than 45 degrees and up to 75 degrees to a rounded apex having a radius of from 0.038 to 0.051 cm, the projectile having an apparent density as hereinafter defined of no greater than 5 grams per cubic centimeter.Such projectiles when propelled at sub-sonic speeds can enter an animal cleanly without causing significant damage to the animal's hide or flesh; the projectile normally comes to rest within the animal's flesh within a relatively short distance from the point of entry irrespective of the distance (within a range of from 1/3 to 18 meters) from which the projectile is propelled towards the animal; if the projectile strikes a bone or semirigid member within the animal, it will normally be stopped or deflected without significant damage to the bone or member.

The projectile is adapted for safely carrying a medicament (e.g. a vaccine, antibiotic or worming compound) or a device (e.g. an electronic locating or marking device as described in U.S. patent No's. 4087791 and 4065753) into the flesh of an animal. The body and nose portions of the projectile could be entirely formed of a uniform mixture of medicament and binder. The projectile may instead be formed of soluble or insoluble rigid low density material and define a central cavity open to the end of the body portion opposite the nose portion in which cavity a medicament or a device may be carried. Preferably, such a cavity has a cylindrical portion which is coaxially located within the body portion of the projectile and has a hemispherical front portion of the same diameter at its end adjacent the nose portion.The hemispherical portion of the cavity smoothly joints the cylindrical portion, thereby avoiding any corners in the cavity, which, if they were present; could cause stress concentration points and resultnat shearing between portions of the projectile upon impact.

For most purposes body portions of from 0.45 to 0.76 cm in diameter are most suitable with body portions of 0.64 cm in diameter being preferred, but some limited applications of shallow implantation, body portions of up to 1.15 cm in diameter may also be suitable.

It has been found that to afford clean effective limited penetration into an animal of such a low density projectile propelled at sub-sonic speed, the nose portion of the projectile should taper generally conically with an included angle of over 45 degrees and up to 75 degrees (with an angle of 60 being preferred) to a rounded apex or terminal end surface having a radius of from 0.038 to 0.051cm. Low density projectiles with hemispherical or parabolically rounded nose portions tend to punch holes in the hide of an animal into which they are propelled at sub-sonic velocities and can thus carry a portion of hide into the wound to provide a source of infection. Also such projectiles upon entering the flesh of an animal will cause substantial trauma and resulting hematoma such that a large welt can immediately be seen to rise on the animal after the projectile enters.Low density projectiles with a conical nose portion having an included angle in the indicated range, but with a pointed instead of a radiused apex, tend to stick into but not penetrate the hide of an animal when propelled against the animal at sub-sonic speeds. Surprisingly, however, projectiles with both the conical nose portion and the radiused apex of the shapes indicated can penetrate the hide of an animal and with little damage to the animal flesh.Penetration by such a projectile may cause only a slit in the hide where it enters, this entry slit having a shorter length than the diameter of the projectile; generally little if any bleeding occurs through the slit; such a projectile normally does not carry a portion of the animal's hide into the wound, and may move through the flesh without causing significant trauma and resulting hematoma so that only a relatively small welt is raised in the area where the projectile enters. Additionally such a projectile seems to penetrate only a limited distance into the flesh of the animal (i.e. 5 to 12.7 cm depending on the age of the animal) irrespective of the distance in the range of 1/3 to 18 meters to the animal from which the projectile is propelled.

Preferably the projectile has a concave surface at its end opposite the nose portion, which concave surface may be provided by the body portion or by a medicament or a device in the cavity. The concave surface produces much greater accuracy of flight for the projectile than does a flat end, presumably because it restricts tipping forces at the edge of the projectile due to escaping gas as the projectile exits from a barrel, and is particularly useful in obtaining accuracy for uniform mass projectiles.

The body of the projectile can have a variety of shapes. Thus, the body can be a smooth cylinder-like shape, as shown in Figure 1, for firing from conventional land and groove barrels. However, with such projectiles made of certain low-density polymeric materials, however objectionable fouling of the gun barrel may occur. This fouling problem may be avoided by using projectiles having a helical body configuration. These helical projectiles can be projected from a barrel having a smooth, helical bore in a spinning mode, preferably with sufficient spin about the longitudinal axis to stabilize the flight of the projectile, by a mechanical or expanding gas propulsion means without objectionable fouling of the barrel.

Prior to the present invention, lead projectiles having helically shaped polygonal bodies were used to achieve extreme accuracy in target rifles and other firearms. British Patent No. 2410 issued in 1855 and Patent No. 1645 issued in 1857 show the use of lead bullets having a helical polygonal body and complementary helically bored barrel. Articles treating the history of guns and bullets discuss these firearm systems. Of interest is the book "Guns through the Ages" by Geoffrey Boothroyd, Crown Publishers, Inc., (1968), (Lib. Congress, Cat.

Card No. 62-15152), at pages 80-85, which describes the Whitworth hexagonal twisted bore and the Lancaster twisted oval bore.

The Whitworth rifles, while being extremely accurate, were not favored since the rifle "fouled very badly after about 20 shots" ("Guns", supra, 84) and required a special scraper to clean the bore after each shot. Accordingly, it is quite surprising that the preferred helical bodied projectiles of this invention do not cause objectionable fouling when propelled through a complementary barrel.

The helical bodied ballistic projectiles which are preferred according to this invention have an elongate body portion which has a configuration which can be geometrically inscribed longitudinally within the volume enclosed by an imaginary solid helix generated by revolving a non-circular plane figure at a constant rate around an axis contained within and perpendicular to the lane of the figure while moving the plane figure along the perpendicular axis at a constant rate. The imaginary helical volume thus has a constant pitch. The axis is preferably at the geometric center of the plane figure.

The plane figure used to generate the helical volume must have a non-circular perimeter wherein all extended, imaginary, straight lines circumscribing, i.e. trangent to, the perimeter of the plane figure intersect at a point on or outside of the perimeter. At least the bearing surface portions of the inscribed projectile, i.e. those surfaces which adjoin the surface of the helical vol ume, have the contour of the helical volume.

Preferably, the body of the projectile is constructed so that no open path exists, within the helical volume, which extends along the complete length of the projectile body. That is, the projectile body plugs or seals the helical volume so as to prevent the passage of another body or material therethrough. This is important when the projectile is to be propelled by an expanding gas propulsion means so that the projectile body can "seal" the complementary barrel to prevent gas leakage therethrough. With mechanical propulsion means the sealing feature is not a necessity.

Advantageous results are obtained when such helical bodied projectiles are propelled, at sub-sonic muzzle velocities, through a complementary barrel, that is, a barrel having a helically twisted bore of the same configuration and dimension as the imaginary helical volume circumscribing the projectile to be propelled through the barrel, the bore of the barrel being free of internal projections contained in conventional land and groove barrels.

In one embodiment of the helical projectile, the helical volume in which the projectile is inscribed is formed by the rotation of a polygon, preferably a regular polygon, around and along the axis as described.

These projectiles would have a body surface comprising a plurality of planar sides twisted around the longitudinal axis of the body to form a helical polyplanar body surface.

In another embodiment of the invention the helical volume in which the projectile is inscribed is formed by rotation of a curved, non-circular figure, such as an ellipse, around the axis as described hereinabove.

This provides a projectile having a helically curved body surface analogous to a threaded bolt, screw, twist drill or similar helically shaper article.

In yet another embodiment, the helical volume in which the projectile is inscribed is formed by the rotation of a plane figure having both curved and straight perimetric portions. Such an embodiment provides a projectile having at least one "flat" or planar portion helically twisted around and along the projectile.

As used herein the term non-circular means that the perimeter is not a complete, perfect circle. It is contemplated, however, that portions of the perimeter may comprise arcs having a constant radius including embodiments wherein the plane generating figure described hereinabove has one or more straight sides but is otherwise circular.

Thus, the term non-circular includes a variety of curved perimeters, polygonal, triangular and rectangular perimeters, as well as perimeters having combinations of curved and straight portions.

As noted above, the projectiles of this invention have a relatively low apparent density to limit their striking power and achieve a controlled penetration as desired.

The apparent density should be 5 grams/cm3 or less. Preferably the apparent density will range from about 1 to about 3 grams/cm3 and most preferably from about 2 to about 3 g/cm3. The apparent density as herein defined is obtained by dividing the total mass of the projectile, in grams, by the apparent volume, in cubic centimeters. The apparent volume is the volume contained within the exterior surface of the projectile, including the volume of cavities and voids formed within the projectile, even though such cavities may communicate with the exterior of the projectiles. Thus, the apparent volume of a projectile having a cavity opening to the rear of the projectile is the same as the volume occupied by a completely solid projectile having the same exterior configuration and dimensions.

Merely adding a cavity to, or creating voids in, the projectile does not change the apparent volume as defined herein. The total mass of the projectile includes the mass of the medicament or electronic device included in the projectile as it is found ready for delivery to the target.

The present invention will be further described with reference to the attached drawings wherein like numbers refer to like parts in several views, and wherein: Figure 1 is a side view partially in section of a first embodiment of a projectile according to the present-invention illustrated with a medicament in a chamber formed therein; Figure 2 is an end view of the projectile of Figure 1; Figure 3 is a side view of a second embodiment of a projectile according to the present invention illustrated with an electronic device secured in a chamber formed therein; Figure 4 is an end view of the projectile of Figure 3; Figure 5 is a side view of a projectile of the present invention showing optional cavities and ballast or labeling means in phantom; Figure 6 is a rear view of the projectile shown in Figure 5;; Figure 7 is a top sectional view of a mounted barrel having a smooth helical polygonal bore complementary to the body of the projectile of Figure 5; Figure 8 is a cross section view along line 8-8 of the barrel of Figure 7; Figure 9 is a perspective view of an alternative embodiment of a projectile showing optional cavities and ballast or labeling means partially in phantom; Figure 10 is a rear view of the projectile shown in Figure 9; and Figure 11 is a cross section at a point along a barrel similar to that shown in Fig urc 7 but having a smooth helically twisted bore complementary to the body of the projectile of Figure 9.

Referring now to the drawings, there is shown in Figures 1 and 2 a projectile according to the present invention generally designated by the numeral 10. The projectile 10 comprises an elongate body portion 12 having a central axis and a cylindrical outer surface 0.64 cm in diameter. The body portion 12 is adapted to fit closely into the inner surface of a barrel from which the projectile is propelled as by being deformed into rifling in the barrel. Also the projectile includes a conical tip portion 14 coaxial with the body portion 12. The base of the tip portion 14 corresponds generally in cross sectional area with the cross sectional area of the body portion 12. The conical tip portion 14 has an apex (included) angle 16 of 60 degrees and has a 0.04 cm radius on its apex or terminal end surface 18, the center of which radius is on the axis of the tip portion 14.

The projectile 10 has a cavity 20 opening through the end surface 22 of the projectile 10 opposite the tip portion 14 which cavity 20 is defined by a cylindrical inner surface 24 smoothly joined at its end opposite the end surace 22 with a hemispherical surface 26 so that no stress concentration points are provided within the projectile 10. As illustrated, the cavity 20 is filled with a medicament 28 such as in the form of a compacted or freeze dried powder, with medicament 28 is shaped to provide a concave surface portion 29 at the end surface 22 of the projectile 10. The edge of the concave surface portion 29 is shown at the end surface 22 of the projectile but could be recessed within the cavity 20.

Figures 3 and 4 illustrate another embodiment of a projectile according to the present invention generally designated by the numeral 30. Like the projectile 10 of Figures 1 and 2, the projectile 30 has a conical tip portion 31 with a base generally corresponding in cross sectional area with the cross sectional area of an elongate body portion 34, a radiused apex or tip surface 32, and a cavity 33, which are respectively shaped like the tip portion 14, tip surface 18 and cavity 20 of the projectile 10. The body portion 34 of the projectile 30, however, is not cylindrical on its outer surface. Instead it has ten flat surface portions 36 of equal width around its periphery, which flat surface portion 36 are evenly twisted about the axis of the projectile 30.These flat surface portions 36 are adapted to fit closely within mating twisted flat surfaces in the inner surface of a barrel from which the projectile 30 is to be propelled to provide a desired rotation during flight of the projectile. Also instead of a medicament, the cavity 33 contains a device 37 secured in place by an epoxy resin 38, which device may be adapted to be electronically activated to locate an animal carrying the projectile. The resin 18 securing the device in place porvides a concave end surface 39 for the projectile 30.

In Figure 5, there is shown a projectile 110 comprising elongated body 112 and tapered nose 114. Body 112 has a surface defined by ten intersecting planes to form sides 116 helically disposed about the axis "a" of projectile 110.

As described hereinbefore, the body of the projectile is of a shape which can be inscribed within the helical volume formed by the constant movement of a regular decagonal plane figure around and along axis "a" and wherein at least portions of the surface of the projectile body have the contour of the helical volume so formed. The projectile thus has an exterior surface having bearing portions which will bear upon the interior surfaces of the bore of a complementary barrel and will follow the helical path of the bore along the barrel. This allows the projectile to rotate about the longitudinal axis as it progresses along the barrel and will exit the barrel in a spinning mode. Preferably, the projectile will exit the barrel with sufficient rotational velocity to stabilize the projectile during flight.The rate of rotation can be controlled by the pitch of the helical surface of the projectile body and complementary bore as described hereinafter.

While projectile 110 is shown as having 10 sides which provide a body cross section having a regular decagonal perimeter, the body surface may comprise any number of sides from 3 up to about 20 or more. As a practical limit the maximum number of sides for a projectile having a diameter of about 0.6 cm should not be in excess of about 20 since beyond this point the perimeter of the cross section of the body approaches a circle and the projectile may have a tendency to ride over the sides of the bore of the barrel without achieving the desired rotational pattern for spin stabilization. The minimum number of sides on the projectile is dicated by stability considerations. A projectile havin large sides tends to be more readily affected by air currents during flight. It is preferred to maintain the width of the sides within the range of about 0.1 cm to about 0.4 cm and that the sides be of equal width.

This corresponds to a range of about 5 to about 20 sides for a projectile having a nominal maximum diameter to about 0.6 cm.

For a body having sides of equal width the relationship is conveniently given by Standard mensuration formulae. When the body has sides of unequal width, it is preferred that the width of all of the sides fall within the range specified above, i.e. a width of between 0.1 cm and 0.4 cm.

As can be appreciated, the body surface of a larger diameter projectile can accommodate a greater number of sides, while a smaller diameter projectile must have fewer sides to maintain the preferred 0.1 cm minimum side width.

The pitch of the helically disposed sides of the projectile can be selected over a wide range, but the pitch should be selected to impart adequate flight stabilizing spin to the projectile. The pitch must be constant for each projectile. The pitch of the helix is the distance between two coils of the helix measured along the longitudinal axis of the body. In other words, the pitch is the distance in which one of the helically disposed sides of the body completes or would one full revolution around the body. Preferably the pitch is between 18 and 40 cm and is most preferably about 20-25 cm to provide a projectile having a "1 in 20" to "1 in 25" twist.

If the helical pitch of the projectile is greatly lengthened, the projectile will not achieve sufficient spin to be properly stabilized during flight. If the pitch is excessively short, the projectile will offer greater resistance to movement along a complementary bored barrel. Greater propulsion forces will be needed to achieve the desired nuzzle velocity. This condition may in turn produce increased friction forces in the barrel, resulting in objectionable wearing and fouling.

Projectile 110 is shown in Figure 5 as including a cavity defined by annular wall 118 opening to the rear of the projectile.

The cavity is optional and can be used to carry a variety of beneficial payloads as will be described in greater detail hereinafter.

Mass 120 is also shown embedded within projectile 110. The mass may be a ballast means, to stabilize the projectile during flight, or may be an active or passive identifying or labeling element such as the passive transponders, i.e. tuned, resonant circuits, described in U.S. Patents Nos.

4065753 and 4,087,791 to which attention is directed for detail.

Nose portion 114 is tapered to provide the desired flight and penetrating characteristics, depending on the preferred target.

Various ogival designs, such as rounded and sharp pointed designs, can be adapted for use with the projectiles of the present invention depending on the specific terminal ballistic characteristics desired. A particularly preferred nose design is the conical configuration having a radiused tip as described herein and shown in Figures 1 to 4 of the drawings.

Figure 6 is a rear view of the projectile 110 shown in Figure 5, showing the cavity defined by annular wall 118 within body 112. len helically disposed planes 115 form the sides of the surface of body 112.

Figure 7 is a cross section view along the length of barrel 130 which is shown retained in mounting block 132. Barrel 130 com prises breech 134 and bore 136. The bore 136 is smooth, that is, the bore has no inter nal projections such as are characteristics of conventional land and groove barrels.

Rather, bore 136 comprises ten sides 138 helically disposed about the longitudinal axis "b" of bore 136. The diameter and pitch of helical bore 136 are complementary to the body surface of projectile 120 shown in Figure 5. That is, the bore has a contour and dimensions identical to the imaginary helical volume circumscribing the projectiles which are to be propelled through the barrel. Thus, the bore 136 coincides with the volume formed by the rotation of the regular decagonal plane figure, as described with respect to projectile 110 hereinabove, around and along axis "b".

Projectile 110 can be propelled through barrel 130 whereby sides 116 of projectile 110 will contact and follow the complementary sides 138 of bore 136 so that as projectile 110 moves through barrel 130, the projectile is forced to rotate about longitudinal axis "a" and exits the muzzle of the barrel in a spinning mode.

Figure 8 is a cross section taken along line 8-8 of barrel 130. Bore 136 is shown having a decagonal perimeter formed by sides 138.

As noted hereinabove, the decagonal perimeter can be circumscribed by imaginary, extended, straight lines which coincide with the straight sides of the perimeter. All such extended lines will intersect at a point either on or outside of the perimeter. Bodies having cross section perimeters wherein such lines intersect within the perimeter would have indentations therein. The complementary barrels would thus be required to have projections in the bore to mate with the projectile properly and would not be smooth bored as defined herein. This combination can produce objectionable fouling.

Figure 9 is a perspective view showing another embodiment wherein projectile 140 comprises a body portion 142 and a tapered nose portion 144. The cross section of body 142 is elliptical as shown by the rear view of projectile 140 (Figure 10). The body 142 has a curved surface which is helically twisted about longitudinal axis "C". An optional cavity defined by annular wall 146 is shown opening to the rear of the projec tile 140. This cavity may be used to carry and release, if desired, a variety of payloads.

In addition, other mass represented by cube 148, shown in phantom, can be incorpo rated in the projectile 140 to advantage as discussed with respect to the projectile shown in Figure 5.

As described hereinbefore, the body of this projectile can be inscribed within the helical volume formed by the constant movement of an elliptical plane figure around and along axis "c" and wherein the surface of the projectile body has the contour of the helical volume so formed, The elliptical plane figure should have significantly different major and minor diameters so as to be non-circular and so that a spin about longitudinal axis "c" can be imported when the projectile is propelled through a complementary barrel. The difference between the major and minor diameter should not be so great as to provide a projectile which will be cxcessively affected by air currents during flight. It is preferred that the length of the minor diameter be about 50 to 90% of the length of the major diameter.

The requirements for the projectiles having curved surfaces are analagous to those for the projectiles having cross sections with polygonal perimeters as discussed with reference to Figure 5 hereinabove.

Figure 11 shows a cross section of a barrel similar to barrel 130 shown in Figure 7, but having a smooth helical bore with curved walls 152 forming an elliptical perimeter.

Barrel 150 is complementary in contour to the body of projectile 140 shown in Figure 9 so that as projectile 140 is propelled through barrel 150, the projectile is caused to rotate about axis "c" and exit the muzzle of the barrel in a spinning mode.

As with the polygonal cross section perimeter shown in Figures 5-8, the ellipical perimeter of the projectile and bore in Figures 9-11 can be circumscribed by a series of imaginary extended straight lines tangent to the perimeter. For the reasons set forth with respect to the polygonal structures described herein, these lines must not intersect within the perimeter in order to be included within the structures contemplated by this invention.

These projectiles can be prepared from any material which has sufficient integrity to be formed into a projectile and propelled from a gun barrel at sub-sonic muzzle velocities without fracture and which provides a finished projectile, including payload if any, having the necessary apparent density.

A variety of materials can be used to form the various projectiles of this invention.

Materials having a density below that of the heavy metals, such as lead, are preferred in order to provide the required mass characteristics. Generally organic materials are preferred, although certain lightweight metals, such as magnesium, can be used with advantage. The preferred organic materials rae polymeric materials such as the various thermoplastic and thrmosetting polymers.

When the projectiles of this invention are used to be impacted on, or implanted in, animals, it is preferred that a biomedically acceptable organic material be used. These materials can also be selected so as to be soluble or insoluble in the target animal body after ballistic implantation of the projectile. Exemplary ot relatively insoluble materials are the synthetic organic polymers such as the polyolefins, e.g. polyethylene and polypropylene, polysiloxanes; polyamides, such as nylon; fluorinated hydrocarbon resins; and ABS polymers. Exemplary of polymers which are soluble in animal bodies, e.g. cattle, are the cellulose derivatives, such as hydroxy propyl cellulose avaibable commercially under the tradename "Klucel" from the Hercules Powder Company.

Metallic projectiles can be used for certain applications. Magnesium is light in weight and can be dissolved by body fluids and thus projectiles of magnesium or combinations of magnesium and organic polymer, e.g. either the exterior or interior comprising magnesium, can be used. While lead is not a preferred material, lead may be incorporated into the projectile as a weight or ballast means or as a coating on the projectile. However, because of possible toxicity, lead is not generally desirable for implantation into an animal body where it can be exposed to the body, e.g. as a surface coating or in an otherwise soluble propectile. Moreover. projectiles having a surface coating of metallic lead have a greater tendency to smear and foul the barrel from which they are propelled due to the peculiar physical nature of lead.Accordingly, projectiles which have a surface substantilly free of metallic lead are preferred.

A variety of inorganic fillers such as calcium carbonate, magnesium carbonate, ferric oxides, and iron powder can be used to alter the solubility properties and/or the density and other physical properties of the projectiles.

For certain applications it may be desired that the projectile rupture on impact with or without signifact penetration, for example, to release a dye or a medicament, such as an antiseptic material or a tranquilizer. Certain waxes or fragile polymeric materials can be used to achieve these results with the whole projectile or only a portion thereof, such as the nose portion, made from the rupturable material.

Lubricants which may aid in the molding and shooting of the projectiles can be incorporated into the projectiles. Calcium stearate, glycerol monostearate, and powdered teflon can be so used with advantage.

The projectiles of the present invention can be formed with internal cavities in which various types of beneficial payloads can be incorporated. The cavity may be left open or sealed with a removable, soluble or porous plug so that the payload can be disseminated following inplantation into the animal. Various types of beneficial payloads and various means of providing sustained release of the payload can be employed such as are described in U.S. Patent 3,948,263, issued April 6, 1976, and U.S. Patent 3,982,536, issued September 28, 1976, to which attention is directed for detail.

Of particular interest is the fabrication of completely soluble projectiles made from hydroxypropyl cellulose or other bodysoluble polymer. The payload can be carried in a cavity in the body of the projectile or admixed and dispersed throughout the solid body of the projectile. After implantation, the projectile completely dissolves in the body, releasing its contents in the animal.

Also of interest are the "solid dose" projectiles where the projectile comprises up to about 95% by weight active ingredient with the remainder being a biologically acceptable binder. Thus, projectiles comprising 90-85% penecillin and 5-10% hydroxypropyl cellulose binder can be molded into the shape of a projectile and used in accordance with this invention.

As noted previously herein, the preferred helical bodied projectiles of this invention can be propelled from complementary barrels without objectionable fouling even after extended use, e.g. several hundred shots. In contrast, projectiles prepared from similar materials which have round bodies, and which are propelled through conventional land and groove barrels to provide spin stabilization, show evidence of fouling after one hundred shots or less, and the barrel must be periodically cleaned to provide maximum performance over an extended period of use.

The invention can be further illustrated by reference to the following Examples.

Example 1 Projectiles similar to that shown in Figure 5 were prepared by an injection molding technique. An intimate mixture of 50 parts hydroxypropylcellulose and 50 parts calcium carbonate was formed by dissolving the hydroxypropylcellulose in 250 parts methanol and stirring in the calcium carbonate to form a thick slurry. The solvent was removed by air drying and the resulting cake was crushed and used to injection mold projectiles using a decagon mold having a 25 cm helical pitch. The projectiles had an apparent density of about 2 g/cm3.

These projectiles were propelled through a complementary barrel at subsonic muzzle velocities. After several hundred shots no objectional barrel fouling in the form of deposits in the barrel or significant loss of velocity occurred. When conventional round bodied projectiles were prepared from the same materials and propelled through a conventional, round land and groove barrel, the barrel showed evidence of fouling and required cleaning for extended use.

Example 2 A .25 caliber (6.35 mm) projectile suitable for long term implantation in cattle and having a helical decagon body configuration similar to that shown in Figure 5 was pre pared 'from polyethylene by injection molding. A small passive transponder was inserted into the center cavity of the projectile. The remainder of the cavity was filled with epoxy resin which was cured in place and the projectile was then sterilized by exposure to ethylene oxide. The projectile had an apparent density of about 2.5 g/cm3.

These projectiles could be propelled through a complementary decagon. barrel without objectionable fouling. When implanted into cattle, the implant sites showed no adverse tissue reaction to the implant. The implanted transponder could be detected by remote electronic detection devices.

Example 3 A projectile which can be dissolved or degraded in the tissue of animals was prepared by injection molding a projectile similar to that shown in Figure 5, and having a cavity therein, from hydroxypropylcellulose.

The decagon projectile was then sterilized with ethylene oxide. A pellet of dry vaccine (Clostridium haemolyticum bacterin) was pressed into the cavity. The loaded projectile had an apparent density of about 2 g/cm These projectiles could be propelled from a complementary decagon barrel without objectionable fouling of the barrel after hundreds of shots. When ballistically implanted into cattle, the projectile was found to have dissolved in the body in about 24 hours.

Example 4 A projectile similar to that shown in Figure 5 was prepared from a composition containing a high loading of penicillin. Ten parts of hydroxypropylcellulose was dissolved in 500 parts of methanol. 90 parts of potassium penicillin G was stirred into the liquid to form a homogenous slurry. After air drying the slurry to remove the solvent, the caked mixture was finely ground. The resulting powders were then compacted into a helical decagon mold having a 25 cm pitch to provide projectiles with an apparent density of about 2 g/cm3.

These projectiles could be propelled through a complementary decagon barrel without objectionable fouling. When implanted into cattle the projectile dissolved in the animal body within about 24 hours.

Claims (16)

WHAT WE CLAIM IS:

1. A projectile having an elongate body portion for close fitting engagement with the inner surface of a barrel from which the projectile is to be propelled and a nose portion coaxial with and tapering generally conically from one end of the body portion at an included angle of greater than 45 degrees and up to 75 degrees to a rounded apex having a radius of from 0.038 to 0.051 cm, the projectile having an apparent density as hereinbefore defined of no greater than 5 grams per cubic centimeter.

2. A projectile according to claim 1 wherein the end of the body portion opposite the nose portion is concave.

3. A projectile according to claim 1 or 2 wherein the included angle is about 60 degrees and the radius of the apex on said nose portion is about 0.04 cm.

4. A projectile according to claim 1, 2 or 3 wherein the body portion has a diameter of between 0.45 and 0.76 cm.

5. A projectile according to any preceding claim 1 having a central cavity with a cylindrical portion coaxial with the projectile and communicating with the end of body portion opposite to the nose portion, and a hemispherical portion on its end adjacent to the nose portion, the hemispherical portion having the same diameter as the cylindrical portion and having its center on the axis of the projectile.

6. A projectile according to claim 5 including a biologically active material in the cavity.

7. A projectile according to any preceding claim 1 whose body portion has a configuration which is inscribed longitudinally within the volume enclosed by an imaginary solid helix generated by revolving a noncircular plane figure at a constant rate around an axis contained within and perpendicular to the plane of the figure while moving the plane figure along the perpendicular axis at a constant rate, the plane figure having a perimeter wherein all imaginary, extended, straight lines circumscribing its perimeter intersect at a point on or outside of this perimeter, at least the surface portion of the inscribed projectile body adjoining the surface of the helical volume having the contour of the helical volume.

8. A projectile according to claim 7 wherein the plane figure has a polygonal perimeter.

9. A projectile according to claim 8 wherein the polygonal perimeter is decagonal.

10. A projectile according to claim 7 wherein the plane figure has a substantially elliptical perimeter.

11. A projectile according to any preceding claim made of a composition containing a biolobically active material.

12. A projectile according to any preceding claim which is soluble in the fluids and cells of a living animal body.

13. A projectile substantially as hereinbefore described with reference to Figs. 1 and 2 of the accompanying drawings.

14. A projectile substantially hereinbefore described with reference to Figs. 3 and 4 of the accompanying drawings.

15. A projectile substantially as hereinbefore described with reference to Figs. 5 and 6 of the accompanying drawings.

16. A projectile substantially as hereinbefore described with reference to Figs. 9 and 10 of the accompanying drawings.