SMALL ARMS PROJECTILE

Abstract

The invention relates to a projectile (1) having an elongated body extending in a longitudinal direction (2), comprising a nose portion (3), a base portion (4) and a middle portion (5) connecting the nose portion (3) and the base portion (4), wherein at least one of the nose portion (3) and the base portion (4) and/or the middle portion (5) comprise structural surface arrangements forming an aerodynamical effective surface (7) and/or a sealing arrangement comprising a plurality of ductile annular sealing areas (8; 9).

Claims

1.-14. (canceled)

15. A projectile having an elongated body extending in a longitudinal direction, the projectile comprising: a nose portion; a base portion; and a middle portion connecting the nose portion and the base portion, wherein at least one of the nose portion and the base portion and/or the middle portion comprise structural surface arrangements forming an aerodynamical effective surface and/or a sealing arrangement comprising a plurality of ductile annular sealing areas.

16. The projectile according to claim 15, wherein the projectile has a solid of revolution shape and an overall length L, the nose portion has an ogive shape having a first length L1 the middle portion has a cylindrical shape defining a bearing surface with a diameter D1 and a second length L2, and the base portion has a frustoconical shape having a third length L3, wherein the overall length L equals 5 to 6 times of the diameter D1, the first length L1 equals 3 to 3.5 times of the diameter D1, the second length L2 equals 1 to 2 times of the diameter D1 and the third length L3 equals 0.1 to 1.5 times of the diameter D1.

17. The projectile according to claim 16, wherein the overall length L equals 5.25 to 5.5 times of the diameter D1, the first length L1 equals 3.1 to 3.25 times of the diameter D1, the second length L2 equals 1.25 to 1.5 times of the diameter D1 and the third length L3 equals 0.1 to 1.1 times of the diameter D1.

18. The projectile according to claim 16, wherein the ogive shape is one of the following shapes selected from the group of tangent ogive, secant ogive, blunted ogive, spherically blunted ogive, Haack series, and von Kar-man.

19. The projectile according to claim 15, wherein the structural surface arrangements comprise at least one of dimples, nubs, ribs, flutes and grooves.

20. The projectile according to claim 19, wherein the structural surface arrangements comprise dimples having a spherical segment shape with a base diameter DB and depth d, wherein the base diameter DB equals 0.05 to 0.3 times the diameter D1, and depth d equals 0.015 to 0.13 times the diameter D1.

21. The projectile according to claim 19, wherein the structural surface arrangements comprise dimples that are arranged only in the nose portion or only in the base portion or in both the nose portion and base portion.

22. The projectile according to claim 20, wherein the dimples are arranged in a way that a minimum center-to-center distance between adjacent dimples equals the base diameter DB, specifically in a way that the center-to-center distance ranges from one to two times the base diameter DB.

23. The projectile according to claim 19, wherein the structural surface arrangements comprise the dimples that are arranged in a pattern of parallel rows and circles, staggered rows and circles or randomly or a combination of these patterns.

24. The projectile according to claim 19, wherein the structural surface arrangements comprise flutes that are arranged longitudinally with respect to the projectile, wherein the flutes are arranged equally interspaced in a circumferential direction in the nose and/or middle portion.

25. The projectile according to claim 15, wherein a plurality of fins extends from the base portion in a radial direction being inclined by an angle(a) of 10 to 30 in relation to a longitudinal direction of the projectile and wherein the fins have a curved shape of radius R.

26. The projectile according to claim 16, comprising a plurality of fins, wherein an outer diameter D2 of the fins, is less than the bearing surface diameter D1 so that the fins do not make contact with the barrel lands and grooves.

27. The projectile according to claim 15, comprising a sealing arrangement wherein the sealing arrangement comprises a first ductile annular sealing area comprising a front sealing ring and a second annular sealing area comprising a rear sealing ring, wherein the sealing rings are arranged in the middle portion.

28. The projectile according to claim 27, wherein each sealing ring is arranged between adjacent annular grooves and diameters DS of the sealing rings are larger than the diameter D1.

29. The projectile according to claim 16, wherein the structural surface arrangement comprises at least one of: dimples, nubs, ribs, flutes and grooves.

30. The projectile according to claim 29, wherein the structural surface arrangements comprise dimples having a spherical segment shape with a base diameter DB and depth d, wherein the base diameter DB equals 0.05 to 0.3 times the diameter D1, and depth d equals 0.015 to 0.13 times the diameter D1.

31. The projectile according to claim 29, wherein the structural surface arrangements comprise dimples that are arranged only in the nose portion or only in the base portion or in both the nose portion and base portion.

32. The projectile according to claim 30, wherein the structural surface arrangements comprise dimples that are arranged in a way that a minimum center-to-center distance between adjacent dimples equals the base diameter DB, specifically in a way that the center-to-center distance ranges from one to two times the base diameter DB.

33. The projectile according to claim 29, wherein the structural surface arrangements comprise flutes that are arranged longitudinally with respect to the projectile, wherein the flutes are arranged equally interspaced in a circumferential direction in the nose and/or middle portion.

34. The projectile according to claim 33, wherein each flute is tapered at each end of the flute and has a triangular cross section and a maximum depth DG of 0.025 to 0.4 times the diameter D1 and has a curved bottom line wherein the radius RB of the bottom line equals 0.25 to 25 times the diameter D1.

Description

SHORT DESCRIPTION OF THE DRAWINGS

[0026] Embodiments will now be described by way of example in view of the drawing, in which:

[0027] FIG. 1 shows a side view of a first embodiment of a projectile according to the present invention;

[0028] FIG. 2 shows a side view of a second embodiment of a projectile according to the present invention;

[0029] FIG. 2a shows a detail from FIG. 2;

[0030] FIG. 3 shows a side view of a third embodiment of a projectile according to the present invention;

[0031] FIGS. 3a to 3c show design variations of the projectile shown in FIG. 3;

[0032] FIG. 4 shows a side view of a fourth embodiment of a projectile according to the present invention;

[0033] FIG. 4a, 4b show variations of the fourth embodiment shown in FIG. 4;

[0034] FIG. 5 shows a side view of a fifth embodiment of a projectile according to the present invention;

[0035] FIGS. 5a to 5e show design variations of the projectile shown in FIG. 5 and

[0036] FIG. 5f shows a detail of FIG. 5e

[0037] FIG. 6 shows a section view of an armor piercing projectile according to the present invention.

DESCRIPTION OF EMBODIMENTS

[0038] Prior to a detailed description of the embodiment according to FIG. 1 some general comments are provided in the following regarding the embodiments.

[0039] The present invention is focussed on a type of superior very long-range projectiles to determine a common thread of characteristics in order to create a perfect design no matter the caliber.

[0040] Such a projectile comprises a nose portion, a base portion and a middle portion connecting the nose portion and the base portion. Flight and/or propulsion characteristics are improved by structural surface arrangements, which form an aerodynamical effective surface and/or a sealing arrangement comprising a plurality of ductile annular sealing areas.

[0041] Such an aerodynamical effective surface improves the exterior ballistic properties wherein a sealing arrangement comprising a plurality of ductile annular sealing areas improves the interior ballistic characteristics by forming an effective sealing area between the projectile and the grooves and the lands during propulsion.

[0042] After leaving the barrel, the deformed ductile annular sealing areas which carry the interior profile of the barrel may also form an aerodynamical effective surface which affects the flight dynamic properties of the projectile surfaces.

[0043] There are embodiments, in which measurements of these characteristics are translated into a formula that could be applied to the diameters of any projectile caliber. There are specific relations between the projectile's calibre or diameter D1, overall length L compared to the length component parts: a) ogive length: L1; b) engraving surface length: L2 and c) boat tail length: L3

[0044] One embodiment shows a projectile, wherein the projectile has a solid body of revolutionary shape, the nose portion has an ogive shape having a first length L1 the middle portion has a cylindrical shape defining the bearing surface with a diameter D1 and a second length L2, and the base portion has a frustro conical shape having a third length L3. The first length L1 equals 3 to 3.5 times, preferably 3.1 to 3.25 times of the diameter D1, the second length L2 equals 1 to 2 times, preferably 1.25 to 1.5 times of the diameter D1 and the third length L3 equals 0.1 to 1.5 times, preferably 0.1 to 1.1 times of the diameter D1.

[0045] Embodiments, which are within the above range are given according to the following table, wherein D1 characterizes the bullet diameter or calibre, L characterizes the overall length, L2 characterizes the length of the middle portion (or bearing surface range), L1 identifies the length of the nose portion (ogive length) and L3 identifies the length of the base portion (boat tail length). In the table the values in brackets are in the metric system and show the values in millimetres (mm), wherein the values without brackets are given in inches.

TABLE-US-00001 D1 L L (min) L2 L2 (min) L1 L1 (min) L3 L3 (min) 0.308 1.694 1.617 0.462 0.385 1.001 0.9548 0.3388 0.0308 (7.8) (43.0) (41.0) (11.7) (9.8) (25.4) (24.3) (8.6) (0.8) 0.3378 1.8579 1.77345 0.5067 0.42225 1.09785 1.04718 0.37158 0.03378 (8.6) (47.0) (45.0) (12.9) (10.7) (27.7) (26.6) (9.4) (0.8) 0.375 2.0625 1.96875 0.5625 0.46875 1.21875 1.1625 0.4125 0.0375 (9.5) (52.3) (49.8) (14.2) (11.7) (30.9) (29.5) (10.5) (0.9) 0.408 2.244 2.142 0.612 0.51 1.326 1.2648 0.4488 0.0408 (10.4) (57.0) (54.4) (15.5) (13.0) (33.7) (32.0) (11.4) (1.0)

[0046] There are embodiments with a specific ogive shape, specifically one of the following shapes: tangent ogive, secant ogive, blunted ogive, spherical blunted ogive, Haack series, von Krmn. Different shape characteristics can be selected for different applications. Specifically for VLD designs, which are suitable for projectiles which maintain for a very long distance in a supersonic state the ogive shape may have a very strong influence on the exterior ballistics (arrange, stability).

[0047] There are embodiments, wherein the structural surface arrangement comprises at least one of: dimples, nubs, ribs, flutes and grooves. Such structural surface arrangement, either formed into the projectile surface (or parts/sections thereof) or obtained during propulsion within the barrel by engraving the interior barrel surface into the exterior projectile surface, may affect the aerodynamic properties, specifically in the boundary layer flow in close proximity to the projectile surface.

[0048] There are embodiments, in which the structural surface arrangement comprises dimples which have a spherical segment shape with a base diameter DB and a depth d wherein the base diameter DB equals 0.05 to 0.3 times the diameter D1 (caliber) of the projectile and the depth d equals 0.015 to 0.13 times the diameter D1. Such a dimple design has shown an advantageous effect on the exterior ballistics of a specific projectile.

[0049] There are embodiments, in which the dimples are arranged in different sections, namely only in the nose portion or only in the base portion or in both, the nose portion and the base portion. In these areas, the dimple structure is not affected by the interior barrel structure during propulsion.

[0050] There are embodiments, wherein the dimples are arranged in a way that the minimum center-to-center distance DC between adjacent dimples equals the base diameter DB. Such a design allows for a dense arrangement of the dimples at the surface. Typically, the dimples can have a center-to-center distance ranging from one to two times the base diameter DB, depending on the dimple size and pattern.

[0051] There are embodiments, wherein the dimples are arranged in a pattern of parallel rows and circles, staggered rows and circles or randomly or a combination of these patterns. The dimples can be arranged so that the outer edges can be either touching or not touching. Such patterns may allow for specific ballistical effects, especially for rotating projectiles.

[0052] There are embodiments, in which longitudinal flutes are arranged equally interspaced in a circumferential direction in the nose and/or the middle portion. These flutes or grooves serve as vortex generators (of varying numbers, widths and depths) at a distance behind a projectile tip to bleed off a percentage of the bow shock wave. The so called bow shock wave is formed at the tip of a rotating projectile in a specific distance in the flight direction. A vortex effect achieved by the flutes in the ogive section reduces the distance between the bow shock front and the tip of the projectile and thereby reduces the drag coefficient and increases the velocity of the projectile. The aerodynamical effects of such flute arrangements are therefore suitable to bleed off the bow shock waves.

[0053] There are embodiments, in which each flute is tapered at each end and has a triangular cross section and a maximum depths DG of 0.025 to 0.4 times the diameter D1 and has a curved bottom line wherein the radius RB of the bottom line equals 0.25 to 25 the diameter D1. This design range allows for an adaption of the vortex/flute design to specific requirements.

[0054] There are embodiments, wherein a plurality of fins extend from the base portion (boat tail portion) in a radial direction being inclined by an angle a of 10 to 30 in relation to a longitudinal axis and have a curved shape of a radius R.

[0055] Boat-tail (aka boattail) projectiles displays a smaller base diameter than a flat base projectile and thus reduces the volume of vacuum behind the projectile leading to greater stability. Boat-tail or end sections tapered at 7.5 degrees are considered standard.

[0056] Base drag has been estimated to be as high as 30 to 50% of total drag. The drag is related the volume of the vacuum behind the base. Boat tails reduce this volume. It has been demonstrated that embodiments with four or eight blades (fins), perpendicular to the surface of the boat tail and not in a position to be engraved by the lands and grooves reduce the vacuum behind the projectile base.

[0057] In such an embodiment, the outer diameter of the fins, diameter D2, is less than the bearing surface diameter D1 so that the fins do not make contact with the barrel lands and grooves.

[0058] There are options with the fins. They can either be right or left handed depending on the barrel's twist rate. A right handed barrel and a right handed fin should result in extended distance of flight as well as extended velocity. On the other hand, a right handed barrel and a left handed fin would result in reduced distance and velocity. This might be advantageous in certain tactics. In addition, the ideal angle of fin curvature has to be determined as clearly the angle would influence the amount of vacuum behind the projectile.

[0059] Embodiments according to the above fin concept comprise four or eight blades perpendicular from the surface of the boat tail as a novel design to increase or reduce velocity and/or distance of projectile flight.

[0060] There are embodiments, wherein the sealing arrangement comprises a first ductile annular sealing area comprising a front sealing ring and a second annular sealing area comprising a rear sealing ring, wherein the sealing rings are arranged in the middle portion. Such an arrangement allows for a double ballistic effect. [0061] 1. Such sealing rings or bands fuse with the lands and grooves of the rifling and thereby prevents any gases from the ignition of the powder to go around in front of the projectile emerging from the barrel. In order to insure higher percentage of gases to be sealed, a first and a second ductile annular sealing area is provided. This is called the interior ballistic effect. [0062] 2. Also, an exterior ballistic effect can be achieved because the rifling destroys the original closed ring shape of the sealing rings or bands by engraving the lands into the circumference of the rings during the travel in the barrel. Therefore, after leaving the barrel an imprint of the rifling is left in the annular sealing areas arranged in the middle portion of the projectile and therefore, forms an aero dynamical effective surface by the ring shapes, which now be a land and groove profile corresponding to the rifling of the barrel. This is called exterior ballistic effect.

[0063] There are embodiments, wherein each sealing ring is arranged between adjacent annular grooves, which have a diameter less that the diameter D1. This allows for a low friction deformation of the sealing ring because the ring volume, which is pushed aside by the barrel rifling during traveling in the barrel, can be received by these annular grooves without affecting or displacing the outside surface of the middle area.

[0064] There are embodiments, wherein the ring profile in a longitudinal direction of the projectile have different shapes to obtain different sealing/ballistic properties. A profile shape may be rectangular, semi-circular, cone shaped, trapezoid, parabolic, hyperbolic or similar.

[0065] There are further embodiments, in which the surface area facing in the travelling direction of the projectile is differently shaped than the surface area facing in the rearward direction. Such an arrangement is further suitable to influence the ballistic properties of the projectile.

[0066] There are embodiments, in which the first sealing ring has a first diameter DS.sub.1 and the second sealing ring has a second diameter DS.sub.2, wherein the first diameter DS.sub.1 is larger/lower than the second diameter DS.sub.2. An additional (first or second) sealing ring with a lower diameter may increase the sealing effectiveness of the first sealing ring which will be partially destroyed by the lands and the grooves of the barrel without increasing the internal friction during propulsion through the barrel.

[0067] There are embodiments, in which a copper jacketed projectile surrounds a penetrator. It leads to an armor-piercing projectile with a penetrator inside the projectile. Such a solid design gives the projectile some armor-piercing capabilities over what would be found in a lead-core copper jacketed non-armor piercing projectile. In combination with the above mentioned aero dynamical effective surface and the sealing arrangement an armor-piercing projectile can be designed so that the linear drag on the projectile is matched to its rotational drag, so that the forward rate of deceleration and an axial rate of deceleration are balanced.

[0068] There are embodiments wherein the penetrator contains one of the following: tungsten carbide, borron carbide, hardened tool steel, oil hardened drill rod and so called nano steel material.

[0069] Now returning to FIG. 1, which shows a projectile 1 according to the present invention. The projectile has an elongated body extending in a longitudinal direction along a longitudinal axis 2 and comprises three sections, namely a nose portion 3 (ogive sections), a base portion 4 (boat tail section) and a middle portion 5 connecting the nose portion 3 and the base portion 4.

[0070] The nose portion 3 has an ogive shape, which starts at the front end of the cylindrical middle portion 5 and ends in a blunted tip 6. The base portion 4 extends from the rear end of the middle portion 5 and has a frustro conical shape with an inclination angle of about 7.5. The cylindrical middle portion 5 has a cylindrical shape of a diameter of D.sub.1, which is typically in a range of 0.17 to 0.80 inches (4.3 to 20 mm) for a small arms projectile.

[0071] The nose portion 3, the base portion 4 and/or the middle portion 5 comprise a structural surface arrangement, which forms an aerodynamical effective surface, which is not explicitly shown in FIG. 1 but only indicated by little circles 7, which indicate a surface structure comprising dimples, nubs, ribs, flutes and grooves or other.

[0072] FIG. 2 shows a second embodiment of the present invention in which the middle portion 5 shows a structural surface arrangement, which forms a sealing arrangement comprising a plurality of ductile annular sealing areas 8 and 9. Both the first sealing area 8 and the second sealing area 9 comprise a sealing ring, namely a front sealing ring 10 and a rear sealing ring 11. The front sealing ring 10 and the rear sealing ring 11 have an outer diameter DS, which is larger than the diameter D1 of the middle portion 5. The diameter DS is at least equal or slightly higher than the greater diameter of the rifling of a suitable gun or handgun barrel (diameter of the grooves). This is because to obtain a close sealing of the propellant from the nuzzle during traveling of the projectile 1 through the barrel. During propulsion the fields of the rifling are cutting or forming nudges in the front end sealing ring 10 and the rear end sealing ring 11. To provide space for the displaced volume of the front sealing ring 10 and the rear sealing ring 11 circular grooves 12 are provided at least in a rearward direction adjacent to the sealing rings 10 and 11. As an option and as shown in FIG. 2 circular grooves 13 may also be formed in the frontward direction of the sealing rings 10 and 11. The outer diameter DGr of these grooves 12, 13 are lower than the outer diameter DS of the sealing rings 10, 11 and the outer diameter D1 of the middle portion 5.

[0073] FIG. 2 shows a cross sectional shape of the sealing rings 10 and 11, which has a sort of an ogive shape with a blunted or cylindrical circumferential middle section (see details in FIG. 2A). Other suitable profile shapes are the following: rectangular, semi-circular, trapezoid, ellipsoid.

[0074] The forward facing 10b and rearward facing surface 10a sections are formed symmetrically according to the embodiment shown in FIG. 2. However, it is possible to form these surface sections differently. Either to obtain better inner ballistic properties (improved sealing, improved forming properties, improved propulsion properties) and/or improved outer ballistic properties (improved aerodynamical behaviour).

[0075] FIG. 3 shows a third embodiment of a projectile 1 according to the present invention. Its shape corresponds to the shape of those projectiles shown in FIG. 1 or FIG. 3. In addition, the base portion 4, or boat-tail section, carries a number of fins 16, which extend radially from the longitudinal axis 2. They are inclined by an angle of 10 to 30 in relation to the longitudinal axis 2 (angle ). The outer diameter of the fins D2 is less than the outer diameter D1 of the middle portion 5. This avoids any contact with the barrel lands and grooves during propulsion. Further, these fins 16 are bended and have a curved shape with a radius RF. The inclination in the rearward direction may be either counter clockwise (FIG. 3a) or clockwise (FIG. 3b). Apart from the embodiment shown in FIG. 3 and FIG. 3a and FIG. 3b with four fins 16, FIG. 3c shows an embodiment with eight fins 16, which are inclined counter clockwise. Further embodiments may have less (at least two) or more fins 16.

[0076] FIG. 4 shows a fourths embodiment of a projectile 1 according to the present invention in which longitudinal flutes 17 are arranged in the nose portion 3. The flutes 17 are arranged equally interspaced in a circumferential direction. In a further embodiment (not shown) these flutes may also be arranged in the middle portion 5 of the projectile 1. Each flute is tapered and has a triangular cross section (see section AA in FIG. 4) with a tip of the triangular section pointing to the center of the projectile 1. The maximum depth DG equals 0.025 to 0.4 times of the diameter D1 and the curved bottom line has a radius RB, which equals 0.25 to 25 times of the diameter D1. A tip section 19 with the length L4 is provided, which is free of a flute arrangement.

[0077] FIG. 4a and FIG. 4b show different shapes and sizes of possible flute arrangements. FIG. 4a shows an arrangement with only four flutes 17a and FIG. 4b shows a high number of flutes 17b, which are arranged with a very low depth DG.

[0078] FIG. 5 to FIG. 5d show different dimple arrangements, which are either arranged in the nose portion 3 and/or in the base portion 4.

[0079] The dimples 20 have a spherical segment shape with a base diameter DB and a depth d (see detail 5f), wherein the base diameter DB equals 0.05 to 0.3 times of the diameter D1 and the depth d equals 0.015 to 0.13 times the diameter D1. The dimples 20 can be arranged so that the outer edges can be either touching or not touching. The dimples 20 can have a center-to-center distance DC ranging from 1 to 2 times the base diameter DB, depending on the dimple size and pattern.

[0080] FIGS. 5 and 5b show different arrangement and sizes of dimples 20 in the base portion 4, wherein the dimples are arranged in circles, which are displaced to each other in a circumferential direction to allow for a denser arrangement of the dimples.

[0081] FIGS. 5a and 5c show a similar arrangement in which the circles are aligned so that rows of dimples 20 occur.

[0082] FIGS. 5a and 5d show different sizes and arrangement of dimples 20, wherein the dimples 20 are arranged in the nose portion 3 and the base portion 4 and FIG. 5e shows an arrangement, where dimples 20 are only arranged in the nose portion.

[0083] FIG. 6 shows an exploded section view of an armor-piercing projectile 101 according to a sixth embodiment having an outer component 102, an inner component 103 and a cap 104. Inside the outer component 102 a cavity 105 is formed into the outer component 102 matching the outer dimension of the inner component 103. The cap 104 seals the inner component 103 inside the outer component 102.

[0084] To combine all three components, first, the inner component 103 or penetrator is pressed into the cavity 105 and the cap 104 is pressed into the recess 106, which is formed at the rear end of the cavity 105 to keep the inner component 103 (penetrator) inside the outer component 102. This arrangement forms the armor-piercing projectile 101.

[0085] In another embodiment the cavity 105 is formed into the nose portion 3 of the outer component 102.

[0086] The cavity 105 and the inner component 103 correspond exactly to each other in shape and dimensions. The outer component 102 is made from a homogenous material specifically metallic material. Suitable materials for the outer component include copper, copper alloys and other similar materials which is softer than the material of the fire arm barrel from which the projectile is fired.

[0087] The inner component 103 is made from a material with a higher density than the material of the outer component 102. Suitable materials for the inner component 103 include solid tungsten, tungsten carbide, nanotechnical materials such as nano steel and others.

[0088] In a seventh embodiment of a projectile 1 according to the present invention, where all the above mentioned features are combined into one projectile 1. A dimple arrangement in the base portion 4, a first and a second ductile annular sealing area in the middle portion 5 and a flute arrangement in the nose portion 3.

[0089] Further variations and embodiments are obvious for someone skilled in the art on the basis of the claims.

REFERENCE SIGNS

[0090] 1 projectile

[0091] 2 longitudinal axis

[0092] 3 nose portion

[0093] 4 base portion

[0094] 5 middle portion

[0095] 6 blunted tip

[0096] inclination angle

[0097] 7 circles indicating aerodynamical effective surface

[0098] 8 sealing area

[0099] 9 sealing area

[0100] 10 front sealing ring

[0101] 11 rear sealing ring

[0102] 12 circular grooves (rear end)

[0103] 13 circular grooves (front end)

[0104] 14 surface sections (forward)

[0105] 15 surface section (rearward)

[0106] 16 fins

[0107] angle

[0108] 17, 17A, 17B flutes

[0109] 18 bottom line

[0110] 19 tip section

[0111] 20 dimples

[0112] 101 projectile

[0113] 102 outer component

[0114] 103 inner component

[0115] 104 cap

[0116] 105 cavity

[0117] DGr diameter of grooves

[0118] DS diameter of sealing rings (DS.sub.1 and DS.sub.2)

[0119] DB base diameter

[0120] DC center-to-center distance

[0121] d depth of dimple

[0122] RB bottom line radius

[0123] DG maximum depth of flute

[0124] RF bending radius fins

[0125] D2 outer diameter fins