Patent Application
20190113318
The present disclosure relates to a small arms projectile.
Generally, rifle cartridges have muzzle velocities (MV) less than 3000 fps (915 m/s). Several cartridge exceptions exist but these are in the low 0.20 calibers (˜5,1 mm) with low projectile weights and/or cartridge cases with large capacities for powder. To increase the MV, one needs to increase the powder charge with a larger cartridge case and/or reduce the projectile weight. Higher velocities can lead to projectile point of impact at greater distances while lower projectile weight can be subject to adverse environmental factors such as lateral drift from crosswinds. Muzzle velocities (MV) are not measured at the muzzle but instead, are measured 10 to 15 feet (˜3 to 4, 5 m) away from the muzzle with an instrument called a Chronograph. So the velocity of the projectile is measured in flight a short distance from the muzzle just as the gyroscopic spin begins to stabilize the projectile.
Improving the aerodynamics to the projectile design leads also to better projectile performance while in flight to the target along with better accuracy. Some typical projectile designs are described in the following:
The so called “Spritzer” projectile designs in the late 19th and early 20th centuries were created to improve greater distances, delivery of greater kinetic energy to target and to improve accuracy.
The boat-tail design projectile made its appearance in the late 19th century. The designs, particularly at a 7.5 degrees configuration decrease base drag thus enhancing greater flight distances before impact.
Very Low Drag (VLD) projectiles made their appearances in the 1980's with improvement up to the 1990's. The VLD designs reduced air resistance, usually measured as Drag Coefficient (DC), of the projectile in flight, which achieved a flatter trajectory as well as reducing lateral drift caused by crosswinds.
Projectiles of many rifle calibers are stabilized by 100 yards (˜91 m), but some take longer. For example, we found the 0.408 CheyTac 419 gr projectile (10, 36mm/27 g) has a smaller Minute of Angle (MOA) at 200 yards (˜183 m) than at 100 yards. Measuring the MOA is an approach to determine accuracy—the smaller the better. A MOA smaller at 200 yards than at 100 yards was interpreted that the projectile was better stabilized at 200 yards rather than at 100 yards.
With several exceptions rifle cartridges during the 20th and early 21st century were restricted to muzzle velocities (MV) of approximately 2800 fps (˜850 m/s) or less. The common thread running through these exceptions were MV greater than 2800 fps with calibers in the low 20's with low weights. Experimental examples of low weight 0.30 caliber projectiles are found with MV up to 3500 fps—a 0.30-06 caliber. A Power Point Transmission (PPT) of a proposed 0.65 caliber tubular 556 gr projectile with estimated MV of 5000 fps is also reported.
The supersonic movement of a rotating projectile through a media such as air results in drag. In this case, drag is defined as a partial restriction of forward motion of a projectile through air.
Shock waves at the projectile's nose and tail—anterior to the boat tail if the projectile has a boat tail—as well as elongated turbulent eddies of air at the base of the projectile are the components of total drag. The latter will lead to the lowering of pressure, and in some cases, leads to a partial vacuum with the loss of kinetic energy of the projectile.
Two types of shock waves are distinguished. First, the Bow Shock (BS) wave at the tip of the projectile and then Oblique Shock (OS) waves along the body of the projectile. One OS wave is more prominent than other waves. Typically, one prominent OS wave where the posterior region of the projectile gives rise to the boat tail, which in turn gives rise to eddy currents of air.
The laminar boundary layer exhibits a very smooth flow of air molecules, while the turbulent boundary layer contains swirls or “eddies” of air molecules. The laminar flow creates less surface friction drag than the turbulent flow, but is less stable. At some distance back from the tip, the smooth laminar flow breaks down and transitions to a turbulent flow. The physics here is based on wing drag and not rotating projectile drag—however one study with rotating projectiles show that both plane and rotating body are similar except the latter are compressed. With regard to rotating bodies, the Magnus Force (MF) must be considered. A number of variables are involved in the MF, but the bottom line is a twist to the projectile in flight. This causes a distortion in the boundary layer leading to an asymmetric profile thickness.
Depending on the projectile's shape, base drag contributes approximately 30 to 50% total drag of a rotating projectile through air. Two main factors cause the drag: 1) Eddies currents of air leading to turbulence and/or 2) Partial to total vacuum at the base of the projectile. A boat tail configuration at the base of the projectile focuses eddies of air and reduces the drag. Presently a 7° boat-tail configuration is considered to give the best performance.
With artillery projectiles, “Base Bleed” has been shown to reduce projectile's base drag. Two approaches exist: a metal ring extends past the projectile's base enclosing 1) a small gas generator or 2) pyrotechnic charges—either one filling the vacuum posterior to the projectile's base. However, Base Bleed has not been shown to be successful in small arms projectiles.
Rotating projectiles, such as bullets are more difficult to control than non-rotating projectiles such as rockets. Even though both exhibit similar ballistic characteristics in flight, there are distinct differences—maneuverability being the most notable example.
The emergence of the extra-long distance projectile (i.e., greater than 2,000 meters) came into being with the 0.408 Cheyenne Tacticall. The 0.408 projectile was based on the concept of Balance Flight (see e.g. U.S. Pat. No. 6,629,669 B2). It is also known from U.S. Pat. No. 8,573,129 B1 to use a single sealing ring to improve the propulsion effect (interior ballistics).
However the problem to be solved still pertains, namely to improve the known basic designs to overcome the known shortcomings and to achieve: e.g. greater distance, better stability, remaining in a supersonic flight situation longer.
The problem also pertains for so-called non-sabot armor-piercing projectile designs. Modern small arms armor-piercing projectiles are made of two components: A jacket of a metal (e.g. copper) alloy soft enough to be engraved by the barrel's rifling and an inner core made up to a highly dense material (e.g. tungsten carbide, depleted uranium, hardened tool steel). A number of studies show that depleted uranium shows potential health risks to those handling the cartridges and as a result, more than likely will be phased out with time.
One approach to substitute depleted uranium led to the field of nano technologies. The focus is directed to changing the molecular structures and/or the crystallic structures of steels and steel alloys to assume new properties. So-called NanoSteel™ and Liquidmetal® are two such examples. One popular approach is to improve use of tungsten carbide designs without going to increased weights and at the same time to obtain the same ballistic properties as shown above.
This problem is solved by a projectile according to claim 1.
According to a first aspect of the present invention a projectile is provided having an elongated body extending in a longitudinal direction comprising
Further aspects and features are obvious for someone skilled in the art in view of the dependent claims, the drawing and the subsequent description of embodiments.
Embodiments will now be described by way of example in view of the drawing, in which:
Prior to a detailed description of the embodiment according to
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.
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.
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.
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.
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
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.
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.
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 Kármán. 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).
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
There are embodiments, in which the first sealing ring has a first diameter DS1 and the second sealing ring has a second diameter DS2, wherein the first diameter DS1 is larger/lower than the second diameter DS2. 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.
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.
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.
Now returning to
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 β of about 7.5°. The cylindrical middle portion 5 has a cylindrical shape of a diameter of D1, which is typically in a range of 0.17 to 0.80 inches (4.3 to 20 mm) for a small arms projectile.
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
The forward facing 10b and rearward facing surface 10a sections are formed symmetrically according to the embodiment shown in
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.
b 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.
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.
In another embodiment the cavity 105 is formed into the nose portion 3 of the outer component 102.
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.
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.
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.
Further variations and embodiments are obvious for someone skilled in the art on the basis of the claims.
1 projectile
2 longitudinal axis
3 nose portion
4 base portion
5 middle portion
6 blunted tip
β inclination angle
7 circles indicating aerodynamical effective surface
8 sealing area
9 sealing area
10 front sealing ring
11 rear sealing ring
12 circular grooves (rear end)
13 circular grooves (front end)
14 surface sections (forward)
15 surface section (rearward)
16 fins
α angle
17, 17A, 17B flutes
18 bottom line
19 tip section
20 dimples
101 projectile
102 outer component
103 inner component
104 cap
105 cavity
DGr diameter of grooves
DS diameter of sealing rings (DS1 and DS2)
DB base diameter
DC center-to-center distance
d depth of dimple
RB bottom line radius
DG maximum depth of flute
RF bending radius fins
D2 outer diameter fins
| Number | Date | Country | Kind |
|---|---|---|---|
| EP17196685 | Oct 2017 | EP | regional |
