Field of the invention

The present invention relates to a projectile suited for rifled barrel weapons.

Background of the invention

A projectile may obtain significantly more accurate trajectory and increased firing range by setting the projectile in rapid rotation around its longitudinal centre axis, and thus create a gyro-stabilising effect on the projectile. Weapons firing projectiles are therefore usually equipped with a rifled barrel, i.e. one or several helical grooves running along the inner surface of the barrel. The raised sections of the helical grooves are often denoted as "lands". The lands are the part of the barrel that engraves into the surface of the projectile, and thus responsible for setting the projectile in rotation when it advances through the barrel. Such rifled barrel weapons are typically rifles, guns, revolvers etc. However, also artillery weapons have such rifled barrels. Ammunition for rifled barrel weapons usually comprises a cartridge, an igniter (primer), a propellant and a projectile. Some projectiles are made of a single material; such projectiles can be referred to as massive material projectiles or non- jacket projectiles. Other projectiles, for example the full metal jacket projectiles, have a soft core typically made of lead and a hard shell or jacket extending around the core. The jacket is the only part in contact with the barrel and is subject to the engraving of the lands, and is made of metals or alloys such as copper or copper alloys.

Projectiles will better utilise the energy of the propellant if it forms a substantially gas tight closure between the projectile and the barrel, i.e. preventing propellant gases to bypass the projectile when advancing through the barrel. Projectiles for rifled barrel weapons should thus be correspondingly dimensioned and be made of materials that are able to deform to enable a close and tight fitting to the inner dimensions of the barrel, both at and in-between the lands. That is, the projectile should have mechanical properties ensuring that its surface region deforms to give space for the lands without inducing excessive wear on the barrel/lands. Another consideration is that projectiles should be made of materials with sufficient mechanical integrity to avoid disintegrating upon exposure to the heavy strains during firing of the weapon.

Another consideration is the friction forces between the projectile surface and the inner surface of the barrel. If the friction is too high the barrel will suffer more wear and there is a risk that the projectile will require a too high force to overcome the frictional resistance between the barrel and the projectile resulting in low and inconsistent muzzle velocities and correspondingly high gas pressures in the propel- lant gases. In the worst case scenarios the gas pressure may exceed the strength of the barrel material resulting in severe damage of the barrel. There is thus a ceiling on the maximum friction force between the projectile and the barrel during firing of the weapon which is accepted.

Further, the projectiles need to avoid leaving residues of jacket material in the barrel after firing. This is caused by the partial melting of the jacket material generated by the friction between the barrel and the projectile. The melting temperature of the jacket should thus not be too low. Moreover, they should have sufficiently high density to ensure acceptable impact energies and provide a sufficiently strong gyro-stabilising of the projectile's trajectory towards its target.

There are thus a set of constraints on the mechanical properties of materials to be used for projectiles in rifle barrelled weapons. Up to date, these demands have usually been met by employing lead or alloyed lead as the bulk material of projectiles, both for jacketed and non-jacketed projectiles. The jacket is usually made of a copper alloy. Both copper and lead are however toxic, both to the user and the environment. From a hunter's perspective copper and lead may also, to some extent, contaminate the meat of the prey. Thus, there is a need and desire for finding non-toxic materials suited for use in projectiles. Prior art

As known to a person skilled in the art of gunnery, the typical construction of small arms ammunition for rifled barrel weapons, such as a rifle, a gun, a revolver, artillery weapons etc., is as shown schematically in Figure 1 a) and Figure 1 b). The ammunition 1 typically comprises a casing 2, an igniter 3, propellant 4 and a projectile 5. The propellant 4 is normally provided as a powder inside the casing 2. From Figure 2, it is shown that prior art projectiles 5 intended for military use typically comprises a core 6, usually made of lead, and a jacket 7, usually made of copper.

There is an increased desire and political pressure in the society for reducing the pollution from toxic metals in the nature. The present standard ammunition for small arms, both for military and civil purposes, contains lead in the projectile either alone, or in combination with a copper jacket. Both lead and copper are toxic, such that shooting ranges and military training facilities may save significant costs by changing to non-toxic materials in the projectiles and thus avoid the need for having ground water protection measures such as collection of drainage water runoff, etc.

The challenge with lead-free projectiles is to find materials with similar properties as lead, i.e. high weight, low hardness and friction. Tungsten (Wolfram) or tungsten-based materials (for example tungsten carbide, ferrotungsten etc.) are materials being used in order to replace lead in projectiles.

From document US 2 805 624 it is known a method comprising pressing and sintering a fraction of spherical iron particles having a relatively large diameter of 300 - 400 microns and a fraction having smaller diameter of about 80 microns together with a suitable binder to form a substantially non-porous briquette adapted for use as projectiles for ammunition cartridges. The density of the projectiles is disclosed to be approaching the density of pure iron, i.e. a density of 7.75 g/cm ³ as compared to 7.86 g/cm ³ of pure iron. The projectiles are reported to be less eroding on the gun barrel than prior art projectiles made from iron powders, which are believed to be due to the heterogeneous surface of the projectile resulting from the relatively soft iron particles bound together with smaller iron particles.

Document DE 20 2005 017039 teaches a projectile for air guns made by thermo- forming/hot working a wire of pure iron. The projectiles may be coated with another metal, for example copper, tin or a polymer as corrosion protection.

Document WO 94/00730 discloses a small arms projectile (1), intended primarily for use with rifle bores, produced from steel with a low carbon (C) content and preferably including tellurium (Te) to an amount of 0.02-0.04 % and lead (Pb) to an amount of 0.15-0.35 %, acting in combination to provide to the steel a high cutting capacity and a lubricant effect that is utilized to reduce the friction wear occurring as the projectile passes the bore. The projectile (1) comprises circumferentially applied grooves and lands (4) and in a specific embodiment a slanted shoulder (5) in the intermediate section between the torpedo section (2) and guide section (3), whereby a circular through hole with unrippled edges is punched through the target upon target shooting. The bullet comprises an anticorrosive coating, preferably electro-chemically applied.

Document US 4 109 581 teaches a projectile for an infantry rifle or a light automatic weapon which comprises a solid projectile body made of soft iron made of an alloy of low carbon steels with less than 0.04% of carbon, 0.20% manganese, 0.05% to 0.18% of aluminium, 0.035% of phosphorus and 0.035% of sulphur, while the caliber is below 5.56 mm., preferably 4.00 mm.

Objective of the invention

The main objective of the present invention is to provide a non-toxic non-jacketed projectile suited for rifle barrelled firing weapons. Moreover, it is an objective of the invention to provide a lead and copper-free non- jacketed projectile acceptable for military use within the Geneva Convention of 1949, and which has more or less similar properties as the ordinary copper jacketed projectiles used today. A further objective of the invention is to provide a projectile with improved trajectory precision and target penetration ability as compared to ordinary copper jacketed projectiles used today.

Description of the invention

The invention is based on the discovery made by the inventor that certain iron qualities containing high fractions of the a-ferrite phase mimic the mechanical properties of copper reasonably well, such that non-jacketed projectiles made from a single homogeneous and coherent lump of a matrix material having a high fraction of a-ferrite constitutes an excellent substitute for the common ammunition comprising lead based projectiles with a copper jacket presently employed by the armed forces and in most civil applications. Tests performed by the inventor have shown that such matric material has excellent mechanical properties for forming projectiles which may attain superior performance in terms of trajectory precision and target penetration ability as compared to present standard military ammunition for rifle barrelled weapons consisting of a lead core and a copper mantle.

Thus in a first aspect, the present invention relates to a projectile for weapons with rifled barrels, comprising:

- an elongated body (1 1) having cylindrical symmetry and which comprises:

- one section (13) shaped into a right circular cylinder of substantially radius, r, and length, L, along a longitudinal axis of the elongated body, and

- one section (14) shaped into a projectile nose,

characterised in that

- the body (1 1) consists of a homogenous, coherent and non-porous matrix material having a composition comprising Fe > 99.400 weight% and C < 0.035 weight%, based on the total weight of the matrix material,

- and wherein the elongated body (1 1) is coated by a corrosion protective coating (12) made of polytetrafluoroethylene (PTFE).

Ammunition will be handled, stored and operated at typical outdoor temperatures up to a maximum of around 70 °C. At these temperatures, the iron -carbon system only exists in the solid phase. As can bee seen from the phase diagram at these temperatures, the thermodynamically stable phases of a matrix material having a composition comprising Fe > 99.400 weight% and C < 0.035 weight%, are either consisting of a pure α-ferrite phase when the carbon content is below the solid solubility of carbon, or a mixture of the α-ferrite phase and minor amounts of the pearlite phase when the carbon content is above the solid solubility of carbon.

A-ferrite is a single phase, solid solution of carbon atoms at interstitial sites in a body-centred cubic crystal lattice of iron-atoms. Due to the relatively huge size of C-atoms as compared to interstitial sites in the Fe-lattice, the body-centred cubic crystal lattice of iron-atoms has limited capacity for taking up carbon-atoms, such that the solubility of C is only 0.005 weight% C at 0 °C and increases with temperature up to a maximum at 727 °C of 0.022 weight% C [2]. The a-ferrite phase, or alpha-iron as it also is denoted in the literature, is a ferromagnetic, soft and ductile form of iron. The α-ferrite phase exists up to a temperature of 910 °C. In the phase diagram shown in Figure 2 [1], the α-ferrite phase is located far to the left and is due to the low carbon content difficult to distinguish from the ordinate axis of the phase diagram.

Pearlite is a two-phased interpenetrating micro structure of about 88 weight% a- ferrite and 12 weight% cementite. Cementite is another name for iron carbide, Fe ₃ C, which is very a hard and brittle material. The mechanical properties of pearlite phase are thus an intermediate between the hard and brittle cementite, and the soft and ductile a-ferrite.

Experiments performed by the inventor have indicated that some amount of the pearlite phase may be accepted in the projectile without significantly compromising the mechanical properties of the projectile. More precisely, the tests have indicated that matrix materials having a Vickers hardness of 150 HVio or less (tested according to the standard; ISO 6507-1 :2005 using a load of 10 kg), are well suited for forming homogenous, coherent and non-porous projectiles. Such projectiles are sufficiently soft to be used in rifled barrel weapons without inducing inacceptable wear or inacceptable high friction against on the lands of the barrel. The limit of

Vickers hardness of 150 HVio or less is a preferred (i.e. not a mandatory) feature of the present invention. Projectiles having somewhat higher hardness may be applied, but they will not function equally well due to higher friction forces against the barrel. In practice, the preferred hardness of the matrix material is obtained by a matrix material having a composition comprising one of the following ranges:

Fe > 99 400 weight ⁰ / ^x o and C < 0.035 weight%;

Fe > 99 400 weight ⁰ / ^x o and C < 0.030 weight%;

Fe > 99 400 weight ⁰ / ^x o and C < 0.025 weight%;

Fe > 99 400 weight ⁰ / ^x o and C < 0.020 weight%;

Fe > 99 400 weight ⁰ / ^x o and C < 0.015 weight%;

Fe > 99 400 weight ⁰ / ^x o and C < 0.008 weight%;

Fe > 99 400 weight ⁰ / ^x o and C < 0.005 weight%;

Fe > 99 400 weight ⁰ / ^x o and C < 0.0005 weight%;

Fe > 99 400 weight ⁰ / ^x o and C from 0.0005 to 0.020 weight%;

Fe > 99 400 weight ⁰ / ^x o and C from 0.008 to 0.035 weight%,

Fe > 99 400 weight ⁰ / ^x o and C from 0.008 to 0.030 weight%,

Fe > 99 400 weight ⁰ / ^x o and C from 0.008 to 0.025 weight% or

Fe > 99 400 weight ⁰ / ^x o and C from 0.008 to 0.020 weight%.

The matrix material of either of the above given ranges of iron and carbon contents, may advantageously be alloyed by one or more of the following elements within the given alloying ranges; Si < 0.15 weight%, Mn < 0.20 weight%, S < 0.04 weight%, P < 0.05 weight%, Cu < 0.03 weight%, Sr < 0.01 weight%, Al < 0.02 weight%, Ti < 0.02 weight%, and Nb < 0.05 weight%. Impurities and other elements may advantageously be kept below a total amount of 0.489 weight%. All weight%-units refer to the total mass of the iron phase.

The alloying elements may have an effect of the hardness of the matrix material, such that, depending on which and the amount of alloying element being applied, the alloying elements may induce a restriction of the maximum carbon content of the matrix material to avoid a hardness of the matrix material above the preferred range. The determination of which alloying elements to be applied at which amounts in an iron alloy to obtain a preferred hardness, is within the ordinary skills of a person skilled in the art. Likewise, the handling and heat treatment of iron alloys may have a profound effect on their hardness. The person skilled in the art is well aware of this effect and how to avoid hardening an iron material, i.e. how to obtain an iron material comprising substantially the a-ferrite phase.

The term "homogenous, coherent and non-porous matrix material" as used herein, means that the matrix material is a single lump or piece of a continuous and massive material having no measurable porosity. Furthermore, the term "the matrix material is substantially composed of the α-ferrite phase" as used herein, means that the matrix material has a composition ranging from only single phased α-ferrite to a composite phase of mostly α-ferrite phase and some pearlite phase within the above given ranges for the carbon content, optionally also including one or more of the above given alloying elements within the above given alloying ranges; Si, Mn, S, P, Cu, Sr, Al, Ti, and Nb. Preferably, the matrix material may advantageously have a hardness in one of the following ranges; from 60 to 150 HVio, from 60 to 140 HVio, from 70 to 130 HVio, from 80 to 120 HVio, from 90 to 1 15 HVio.

The term "right circular cylinder section (13) of substantially radius r and length L" as used herein, means that a part of the projectile is shaped into a regular right circular cylinder within practical limits for industrial production. That is, the term "right circular cylinder" is not to be interpreted in the strict mathematical sense of the term. Slight deviations in the radius (and thus diameter) within one or two orders of magnitude of microns may occur along the length L of section (13).

Section (13) is the part of the projectile which will be in contact with the inner wall of the barrel and be mildly deformed by the lands of the rifled barrel. Thus the radius r and the length L of section (13) must be adapted to the dimensions of the barrel and chamber of the actual weapon. However, the present invention is not bounded by any limit of r and L. The projectile according to the invention may be made into any known and conceivable calibre for present and future rifle barrelled weapons, ranging from small firearms to heavy artillery. Examples of suited calibres includes, but is not limited to, calibre 22, 5.56x45mm NATO, 7.62x5 lmm NATO, 9mm NATO, .223 Remington, and 12.7x99mm NATO.

Also, even though the projectile of the invention is suited as substitute for present projectiles for rifle barrelled weapons, it may of course be applied for non-rifle barrelled weapons. The dimensioning of the projectile, including the adaption of the radius r and the length L, is within the ordinary skills of a person skilled in the art.

The projectile according to the present invention obtains its favourable mechanical properties by the choice of material, i.e. the single homogenous, coherent and non- porous iron phase of the projectile. Thus the projectile of the invention may be employed as is, i.e. without any surface coating, due to the favourable softness and ductility combined with the excellent mechanical integrity of the a-ferrite phase enabling firing the projectile in a weapons with a rifled barrel without inducing unacceptable damage/wear on the lands and/or the inner surface of the barrel, or without leaving any residues of the projectile inside the barrel.

However, a-ferrite phase iron has a poor corrosion resistance. Surface corrosion, and in particular rust, is highly detrimental to the friction performance of the projectile and induces unacceptable wear on the barrel, and needs to be avoided. The projectile of the invention may thus advantageously be coated with a corrosion protective coating to ease the storing and handling of the projectile, i.e. to ease the precautions required to avoid the surface of the projectile from corroding during storing and handling. The corrosion protective coating may be any known or conceivable coating able to protect iron from being corroded upon contact with e.g. moisture/water and oxygen. The corrosion protective coating may have any thickness as long as the diameter of the coated projectile is within the dimension specifications of ammunition. In practice, the coating may advantageously have a thickness of less than 100 μιη, preferably less than 50 μιη, more preferably less than 25 μιη, most preferably less than 15 μιη. The corrosion protective layer may be deposited or formed in any known or conceivable manner known to a person skilled in the art. Examples of suited methods includes, but is not limited to; chemical vapour deposition, plasma enhanced vapour deposition, sputtering, etc.

The corrosion protective coating may provide a further beneficial effect by being a an intermediate "barrier layer" between the iron phase of the projectile and the steel phase of the barrel which reduces the friction forces between the inner surface of the barrel and the surface of the projectile. A lowered friction is advantageous by reducing the wear on the barrel and by giving the projectile an increased and more consistent muzzle velocity and thus improved target penetration ability and trajectory accuracy. Thus it is preferred to include a corrosion protective layer having a friction reducing effect on the projectile according to the invention, but this should not be considered as a mandatory and essential feature of the present invention since the corrosion protection of the projectiles may be obtained by other means (by e.g. ensuring the projectile is stored and handled without contact with moisture/water) and the projectile may be fired without any layer on its surface.

An example of a suited corrosion protective coating which has the beneficial of reduced friction is polytetrafluoroethylene (PTFE). PTFE is often sold under the trademark name TEFLON®.

An especially preferred corrosion protective coating is a coating sold under the trademark name XYLAN® 1424/F9426 BLACK, supplied by Whitford Plastics Ltd of 10, Christleton Court, Manor Park, WA7 1 ST Manor Park, Cheshire, England. XYLAN® 1424/F9426 BLACK is an aqueous based, resin-bonded dry-film lubricant coating containing polytetrafluoroethylene and may be applied by spraying or bulk deposition (including electrodeposition) techniques. Substrate preparation is limited to a solvent wash or vapour degreasing. The especially preferred coating of

XYLAN® 1424/F9426 BLACK may be deposited onto the projectile of the invention by spraying in a chamber at 180 °C until a layer of dried XYLAN® 1424/- F9426 BLACK of thickness in the range from 1 to 25 μιη, preferably from 5 to 20 μιη, more preferably from 10 to 15 μιη, and most preferred from 12 to 13 μιη covers the surface of the projectile. The thicknesses are given for the coating in the dry and cured state after drying at 180 °C - 200 °C for a period of 200 minutes or more. If the curing/drying temperature is increased to 220 °C, the curing times may be considerably shorter. The XYLAN® 1424/F9426 BLACK is not recommended cured and dried at higher temperatures.

The projectile according to the invention is to be regarded as a non-jacketed projectile since the coating on the projectile body is too thin to give any significant contribution to the mechanical properties of the projectile with the exception of the friction towards the barrel. Thus, it is the projectile body which provides the required softness and mechanical integrity allowing the projectile to function as ammunition for barrelled weapons. This means that the projectile body should have a softness and ductility allowing it to deform by the lands of the barrel to form a gas tight closure with the barrel and at the same time a mechanical resilience allowing the projectile to withstand the acceleration forces during firing of the weapon and then to withstand the drag forces during the flight towards the target without decomposing or deforming (more than caused by the lands).

Any known or conceivable process for shaping the single homogenous, coherent and non-porous matrix material of the invention into projectiles may be utilised by the present invention, both hot processes involving melting and solidification and cold processes. This includes, but is not limited to; moulding or box casting molten iron or iron alloys into work pieces for projectile bodies, casting molten iron or iron alloys into ingots that are subsequently processed into several work pieces for projectile bodies. The work pieces may be machined in any known or conceivable way to obtain the intended dimension and geometry of the projectile, for example by being machined directly from ingot bars to correct projectile geometry in a lathe, etc. An example embodiment of the projectile according to the invention, having a corrosion protective coating, is illustrated schematically in Figure 3. The projectile 10 is made of one continuous iron phase 1 1 and is given a design which comprises a section 13 being a right circular cylinder of radius r and length L along the longitudinal centre axis indicated by the stapled line from A to A' . The front section (14) of the projectile is tapered to form a nose of the projectile. The corrosion protective coating is indicated by the thick line marked with reference number 12.

It should be noted that the dimension of the projectile will be dependent on the characteristics of the weapon. The specific type of ammunitions or the specific types of weapons will not be described herein as this is considered known to a person skilled in the art.

List of figures

Fig. 1 a) and b) illustrate a cross section of a prior art type of ammunition;

Fig. 2 is a phase diagram of the Fe-C system;

Fig. 3 illustrates an example embodiment of the projectile. Fig. 4 is a photo of an example embodiment of the projectile after firing;

Fig. 5 corresponds to fig. 4, where the lands markings on the projectile are indicated;

Fig. 6 is a diagram showing curves indicating the press force needed to press standard NM255 steel-cored projectiles through a section of a gun barrel; Fig. 7 is a diagram showing curves indicating the press force needed to press projectiles according to an example embodiment of the invention through the same section of a gun barrel as the tests shown in Figure 6;

Fig. 8a) is a photograph of a paper target applied in a test firing of samples of projectiles of the invention.

Fig. 8b) is a photograph of a paper target applied in a comparison test firing of samples of standard NM255 projectiles. Example embodiments of the invention

The invention will be described in further detail by way of example embodiments of the invention.

Example embodiment 1

The first example embodiment of the invention is schematically illustrated in Figures 4 and 5, which are photographs of the projectile after firing. Reference number 10 is the general reference to the projectile, 1 1 is the body and 12 is the coating. Reference number 20a, 20b and 20c are the land marks, i.e. areas where a portion of the body 12 is worn off and/or deformed due to contact with the lands of the barrel. The photograph of Figure 5 shows the same example as in Figure 4, but contains white lines to better indicate the land marks 20a, 20b and 20c.

The body 1 1 was of direct reduced iron with less than 0.015 % carbon made by reducing fine grained hematite or magnetite iron ore with hydrogen as reducing gas, rolled to cylindrical bars of diameter 6 mm. The bars were cut into 30 mm long ingots or work pieces, where each was machined into a projectile body of 5.56 mm diameter and total length of 24.75 mm. Then a 1 to 5 μιη thick layer of diamond like carbon of type a-C:Cr + a-C:H (this corrosion layer is not part of the invention) was deposited by plasma enhanced vapour deposition. As shown by the black colour on the photographs, the coating was mainly applied at the right circular cylinder section of the projectile.

Example embodiment 2

A set of projectiles having dimensions and shape corresponding to projectiles of standard NM255 ammunition (5.56x45 mm) were machined in a lathe, from round bars of diameter 0 10 mm. The bars were made from a single homogenous, coherent and non-porous iron phase of substantially ferrite, with a Vickers hardness of 1 15 HVio, having a composition of: C = 0.0132 weight%, Si = 0.0887 weight%, Mn = 0.155 weight%, P = 0.00052 weight%, S = 0.0039 weight%, Cr = 0.013 weight%, Ni = 0.021 weight%, Cu 0.01 18 weight%, Nb = 0.0025 weight%, Ti = 0.0607n weight%. Fe = 99.63 weight%. Other minor impurities together were ca. 0.006 weight%. The projectiles were sprayed with XYLAN® 1424/F9426 BLACK and dried and cured at 180 °C for 150 minutes. The resulting coating had a thickness of 12 μιη.

Then friction between the projectiles and a gun barrel was measured by pressing samples of the projectiles at a constant velocity of 0.5 mm/s through a 50 mm long section of a machine gun barrel by a piston, and registering the force needed to press the projectile through the barrel. A total of five tests were made on the second example embodiment of the invention and five equal tests were made on projectiles of standard NM255 ammunition, which have a steal core and copper jacket. The obtained test results are given in chronological order in Table 1. "BM-1" stands for the first sample of the second example embodiment of the invention while "NM255-1 " stands for the first sample of the standard projectile.

Table 1

The obtained pressure curves as a function of displacement through the gun barrel are shown in Figure 6 for the standard NM255 projectiles and in Figure 7 for the projectiles of the second example embodiment. As seen from the Table 1 and Figures 6 and 7, the projectile of the second example embodiment has a friction against the barrel of nearly one fifth of the standard NM255 projectiles.

Four samples of the same set of projectiles were test fired by mounting a HK 416 assault rifle in a rig and shooting at a paper target at a distance of 100 m. Figure 8 a) is a photograph of the paper target showing the trajectory accuracy of the four test specimens of the invention. The result corresponds to an accuracy of 0.9 minutes of angle (MOA). A minute of angle corresponds to a trajectory deviation of 26.59 mm at 100 m firing range.

As a comparison, four samples of standard NM 255 ammunition were fired in the same rig. Figure 8 b) is a photograph of the paper target applied in the comparison test. This result corresponds to an accuracy of 2.1 MOA.

The test also involved four test firings with the same test rig and weapon of the same caliber ammunition with present standard military ammunition having a lead core and copper mantle. For these test firings, we do not have a photograph of the paper target, but the test firings gave an accuracy of 1.9 MOA. Additional tests on the same example embodiment of the projectile of calibre

5.56x45 mm have been performed with the same test procedures as described above. The new series of tests applied 1 1 projectiles with a XYLAN® 1424/F9426 BLACK coating for the friction tests and 25 projectiles for the shooting tests.

All 1 1 of the test projectiles were found to exhibit a friction of only 30-40 % of the friction exhibited by similar calibre NM255 projectiles. Thus the projectiles according to the invention may reduce the wear on the rifle barrel by as much as 60 - 70 %. The shooting tests were performed with 100 m firing range using a standard HK416 assault rifle. The accuracy was found to be as low as 1.4 MOA, i.e. the spreading was within a circle having a diameter of 40 mm.

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