MXPA00005912A - Lead-free tin projectile - Google Patents

Abstract

There is provided a lead-free projectile (10, 30, 40, 42, 44) suitable for use as a bullet to be fired from a pistol or rifle. The projectile has a metallic jacket (12, 46) enveloping a metallic core (16). The core is formed from a high purity tin and has deformation properties similar to that of lead based projectiles without the environmental hazards associated with lead.

Description

PROJECTILE OF THIS OR LEAD FREE Field of the Invention This invention relates to lead-free projectiles fired from rifles and pistols. More particularly, to a copper-jacketed bullet having a substantially pure tin core exhibiting similar performance characteristics. to those of lead without presenting the environmental risks of lead.

Background of the Invention Most bullets fired from pistols and rifles have a copper-based alloy core, which means that the core is composed either in total form or in more than 50%, by weight, per lead. The environmental risks of lead are well known. Bullets containing lead shot into the ground are suspected to cause soil water contamination through leaching. Another problem facing fencers is that when a bullet that has been exposed to lead is fired, a powder containing the lead is emitted from the projectile. These lead fumes are toxic and, if they are Ref.120940 inhaled, 'pose a risk to the shooter. There is an additional risk, the lead is leached into the soil water from the non-reclaimed blasts. Many alternatives to a bullet with a lead nucleus have been described. U.S. Patent No. 5,399,187 to Mravic et al discloses a core of the sintered bullet, formed of a combination of a material having a lower density than that of lead and a second material having a greater density than The Lead. A combination described is a mixture of lead and tungsten. U.S. Patent No. 5,500,183 to Noordegraaf et al, discloses a non-jacketed bullet formed from a tin based alloy containing as an addition of the alloy one or more of the copper, antimony, bismuth and zinc . U.S. Patent No. 5,679,920 to Hallis et al, discloses jacketed bullets having a core formed of twisted and stamped strands of zinc wire. Although the bullets described in the prior patents of the United States of America are lead-free, the cores of these bullets are harder than lead, causing bullets to have an unacceptable degree of rebound. In addition, zinc-containing cores may also pose a risk to the environment. Zinc fumes are pointed out in the ASM Handbook, Volume 2, which are suspected of having a detrimental effect on health. < Therefore, there remains a need for a projectile that is both lead-free and zinc-free and has performance characteristics similar to those of a bullet with a lead-based core. Among the performance characteristics of lead that improve the performance of the bullet are malleability, density and low cost. Accordingly, it is an object of the invention to provide a lead-free projectile with proposed characteristics similar to those of lead without the risks to the lead environment. It is a feature of the invention that the projectile has an essentially pure tin core surrounded by a copper alloy jacket. Among the characteristics of the invention are that the projectile has similar characteristics to those of lead and, being free of lead, that it has a reduced impact on the environment. The projectiles are suitable for all types of jacketed bullets, including pistols and rifles. The projectiles of the invention are useful for soft tip, fragtable, and hollow point bullets, as well as other configurations of the bullet. According to the invention, a lead-free projectile is provided. The lead-free projectile has a metal jacket with an external surface defining an aerodynamic projectile and an internal surface defining at least one cavity. The at least one cavity is filled with essentially pure tin having an elastic limit of less than 20 MPa. The above objects, features and advantages will become apparent from the specification and drawings that follow. Figures 1 and 2 illustrate in cross-sectional representation the rifle bullets according to the invention. Figures 3-5 illustrate a cross-sectional representation of the gun bullets according to the invention.

Detailed description of the invention With reference to Figure 1, a projectile '10 according to the invention has a metallic jacket 12. The metallic jacket 12 has an internal surface 14 defining at least one cavity which is filled with a core material 16 which is free of lead. Lead-free, it is proposed to mean that lead is intentionally added as an addition to form the alloy. Although, from an environmental point of view, a zero addition amount of lead is desirable, incidental lead impurities, in an amount of up to 0.05% by weight, are within the scope of the invention. A preferred core material 16 is essentially pure tin. An outer surface 18 of the metal jacket 12 has an aerodynamic profile. Typically, the outer surface is generally cylindrical in shape with an inwardly tapered front portion 20, a central portion 22 of a substantially constant diameter and a bead portion 24 that is generally perpendicular to the body portion 22. A transition portion 26 between the body portion 22 and the heel portion 24 can be of a relatively narrow radius, or, as illustrated in Figure 1, a tapered portion, referred to as a tail or can back. The metallic jacket 12 is formed of any suitable material such as copper, aluminum, copper alloys, aluminum or steel alloys. Zinc-containing copper-based alloys are preferred with a gold copper alloy (nominal composition by weight of 95% copper and 5% zinc) which is more preferred. The core material 16 is formed of a metal having deformability characteristics similar to those of lead. The lead alloy L50042 (nominal composition by weight, at least 99.94% lead) has an elastic limit of between 12 and 14 MPa. Pure tin of Grade A (nominal composition in weight of 99.85% tin as a minimum) has an elastic limit of 11.0 MPa. Preferably, the metal cores of the invention have an elastic limit of less than 20 MPa and, preferably, the elastic limit is from about 8 MPa to about 15 MPa. The hardness is less than 20 HB, and preferably, from about 3 to about 5 HB. The values of both the elastic limit and the hardness are at room temperature, between approximately 20 ° C and 23 ° C. As illustrated in Table 1, small additions of most alloy elements increase the yield strength and hardness of a tin-based core. The less deformable the core, the greater the risk of rebound.

Table 1 A preferred metallic core 16 is essentially pure tin. The tin-based core has a maximum, by weight, of 0.5% in total of the additions for the formation of the alloy and not more than 0.25%, by weight, of any addition for the formation of the alloy. More preferably, the total amount of all additions for the formation of the alloy is less than 0.2% by weight, with no more than 0.1% by weight, of any addition to form the alloy. Certain elements suspected of generating toxic fumes or causing risks to the environment must be present in smaller quantities. As outlined in ASM Handbook, in Volume 2, these damaging additions include arsenic, lead, cadmium and zinc. Each deleterious addition is preferably present in an amount, by weight, of less than 0.005% and, more preferably, in an amount of less than 0.002%. A preferred material for the metallic core is specified by ASTM (American Society for Testing and Materials) as a Grade A tin. This metal has a minimum tin purity, by weight, of 99.85% tin and maximum residual impurities of 0.04. Antimony%, 0.05% arsenic, 0.030% bismuth, 0.001% cadmium, 0.04% copper, 0.015% iron, 0.05% lead, 0.01% sulfur, 0.005% zinc and 0.01% (nickel + cobalt). Additions for the formation of the alloy that do not significantly change the yield strength or hardness of the tin based alloy may be present in larger amounts. For example, it is believed that magnesium additions, by weight, of up to 5% and, preferably, from about 1.5% to about 2.5% are suitable. The essentially pure tin is heated above its melting temperature and the molten metal is poured into a precursor of the cup-shaped jacket. The precursor of the sleeve is then stamped mechanically to a desired sleeve shape. Figure 1 illustrates a projectile 10 suitable as a bullet for soft-tipped, jacketed rifle. The density of tin, of 7.17 grams per cubic centimeter, is approximately 63% of that of lead, of 11.35 g / cm3. Therefore, the projectiles of the invention have a weight that is less than that of the weight of a projectile with a lead core of equivalent dimensions. The reduced weight does not. Significantly degrades the operation of the proposed pistol bullets for short range use. For rifle bullets, a smaller increase in the length of the bullet will achieve a bullet weight similar to a lead core projectile. For example, a soft-tipped, copper-clad projectile of 5.56 millimeters, of the type illustrated in Figure 1, has a nominal length of 1.7 cm (0.675 inches) and a total weight of 3.56 g (55 grains) when formed from lead. Increasing the length to 2.10 cm (0.825 inches), a projectile with an essentially pure tin core achieves the same weight.

Figure 2 illustrates a second projectile 30 useful as a rifle bullet. The projectile 30 has a fragmentation design with a hollow nose nose 32 formed from a metal jacket 12. The metal jacket 12 defines a back pocket filled with essentially pure tin 16. A closure disk 34, typically formed from bronze, is snapped into the bead portion 24 of the projectile 30 to prevent extrusion of the tin when the projectile is accelerated rapidly during firing. Optionally, one or more cup-shaped inserts 36 are placed between the essentially pure tin 16 and the hollow nose nose 32. As described in United States Patent No. 5,385,101 to Corzine et al., The insert cup-shaped 36, or multiple inserts, minimize the extrusion of the metal material from the cavity towards a game animal hit by the projectile 30. The integrity of the metal jacket 12 can be ramified by impact with a bone, or another hard structure, or perforated by tips of petals of the nose of hollow point. Cup-shaped inserts 36 provide extra strength to prevent loss of core material. Figures 3-5 illustrate the projectiles of the invention for firing from a gun. Figure 3 illustrates a projectile 40 referred to as a soft-tipped, jacketed pistol bullet. The portion 41 of the nose is formed essentially of pure tin. The exemplary calibres for projectile 40 are a soft-tipped, jacketed projectile for Luger of 9 millimeters, a soft-tipped projectile, jacketed, for 0.38 Special, a soft-tipped, jacketed projectile, for 0.40 S &W, a projectile Soft tipped, copper-clad for 0.45 Auto, a soft-tipped projectile, 5.56mm jacketed, and a soft-tipped projectile, jacketed for 10mm Auto. The structures illustrated in Figures 3-5 which are similar to those illustrated and described in Figures 1 and 2 are identified by like reference numerals. The projectile 42 illustrated in Figure 4 is a hollow point, jacketed projectile. The portion 41 of the nose includes an annular cavity 43 open towards the front, which extends rearwardly. Optionally, the portion 32 of the nose of the metal jacket 12 extends into the open annular cavity 43. An exemplary gauge for this projectile is a hollow point bullet, copper-jacketed for 9 mm Place. Figure 5 illustrates a projectile 44 for manual, fragmentation gun. A metal, fragmentation, generally H-shaped, shirt 46 has a centrally located portion 47 separating a rear cavity 48 and a front cavity 50. Both the rear cavity 48 and the front cavity 50 are filled with the metal core material 16. A sealing disc 34 may be snapped to the bead portion 24 of the metal jacket 46 to retain the metal core material 16 in the rear cavity 48. The projectiles of the invention are suitable for use with any cartridge conventional, including without limitation, a centered firing gun, a centered firing rifle, a centered firing revolver and firing on flanges. The projectiles are not limited to the specific gauges and the essentially pure tin cores of the invention are suitable for any jacketed projectile that currently has a metallic lead core. Projectiles of an effective size to be fired from a gun that uses centered shot cartridges range in size from caliber 0.25 to approximately caliber 0.458 and projectiles of an effective size to be fired from a rifle that uses central firing cartridges vary in Size from caliber 0.22 to approximately caliber 0.50. The projectiles for the firing cartridges on rims are typically 0.22 caliber for both gun and rifle.

Although the projectiles of the invention are particularly designed to be at least partially jacketed within a metal jacket, it is within the scope of the invention to form non-jacketed projectiles from the substantially pure tin material described hereinbefore, particularly for the shot from a gun. The advantages of the invention will become apparent from the following examples.

EXAMPLES Example 1 The soft-tipped, copper-clad, 9mm Luger projectiles, of the type illustrated in Figure 3, were fabricated with an essentially pure tin core and the firing tests were conducted using a standard SAAMI test barrel (Sporting Arms and Ammunition Manufacturers Institute) for 9mm Luger. All the bullets tested were found to possess optimal interior and exterior ballistic properties in addition to a predictable bullet flight, accuracy and low rebound power. Due to the intensity of the tin which is lower than that of the lead, the 9 mm Luger projectiles of the invention weighed an average of 6.80 g (105 grains), compared to a Luger bullet of 9 mm conventional lead core similar design that weighed an average of 9.53 g (147 grains).

Example 2 The soft tip projectiles, copper-clad for Smith & Wesson's (S &W) of 0.40 were manufactured with an essentially pure tin core. The firing tests were carried out with these bullets using a SAAMI standard test barrel for S &W of 0.40. All bullets were found to possess optimal interior and exterior ballistic properties in addition to a predictable bullet flight, accuracy and low rebound potential. Because the density of tin is lower than that of lead, the S & W projectiles of 0.40 of the present invention have an average bullet weight of 9.07 g (140 grains) when compared to a projectile for S & W of 0.40 conventional with dimensions that have an average bullet weight of 11.66 g (180 grains).

Example 3 The hollow-point projectiles, clad with copper for Luger of 9 millimeters, of the type illustrated in Figure 4, were manufactured with an essentially pure tin core. The firing of projectiles from a standard 9mm Luger test barrel showed that all bullets have optimal inner and outer ballistic properties in addition to a predictable bullet flight, accuracy and low rebound potential. The 9 mm jacketed hollow point projectiles of the invention had an average weight of 6.74 g (104 grains) compared to 9.53 g (147 grains) for hollow point bullets, jacketed, for Luger 9 mm, of material of comparable standard production. Ten bullets of the invention were loaded into a standard 9mm Luger projectile sheath with Ball Powder® propeller ("BALL POWDER" is a registered trademark of Primex Technologies, Inc., St. Petersburg, Florida). The propeller is available from Olin Corporation, East Alton, Illinois) to a loaded cartridge length of 2,832 cm (1,115 inches) + 0.025 cm (0.010 inches). The velocity of the projectile in the shot was 335 m / s (1,100 feet per second) + 6 m / s (20 feet per second).

According to the Federal Bureau of Investigation ammunition test protocol, five of the bullets of the invention were fired on a gelatin block from a distance of 3.05 m (10 feet). The bullets had an average speed of 348.7 m / s (1,144 feet per second) and penetrated the gelatin at an average depth of 28.3 cm (11.15 inches). Another five impacts were fired at a block of gelatin covered with a layer of mahón covered by a layer of fluff. The bullets were fired from a distance of 3.05 m (10 feet) and achieved an average speed of 353.6 m / s (1,160 feet per second) and a penetration depth of 28.9 cm (11,375 inches). Both the velocity and the depth of penetration of the bullets of the invention compare very favorably with the standard lead core projectiles. Other properties including the proposed diameter and weight retention were comparable with those of conventional lead projectiles.

Example 4 The soft-nose, copper-clad, 9mm Luger projectiles fabricated with an essentially pure tin core, as described in Example 1, were loaded into shells for the standard 9mm projectile, as described in FIG. Example 3 and were compared with a 9mm Luger zinc core bullet of the type described in U.S. Patent No. 5,679,920. The average weight of the bullet of the invention was 6.80 g (105 grains) and that of the zinc-based bullet, 6.48 g (100 grains). When fired at a temperature of 21 ° C (70 ° F), the bullets of the invention had an average speed of between 352 and 379 m / s (1,155 and 1,245 feet per second). an average weight of between 374 and 382 m / s (1,226 and 1,252 feet per second) The accuracy of the bullets was evaluated Five shots were fired from each of the test barrels for Luger of 9 millimeters different than a target that it was at a distance of 45.7 m (50 yards) Each test was repeated five times and the extreme dispersion, in inches, between each set of the five shots was recorded in Table 2. The extremely high accuracy of the projectiles of the invention It approximates the degree of correspondence.

TABLE 2 Smooth Tip Shells, Jacketed, 9mm with Tin Core Test # BBL # 1 BBL # 2 BBL # 3 1 2.39 cm (0.94") 3.10 cm (1.22") 2.59 cm (1.02") 2 5.82 c (2.29") 4.98 cm (1.96") 1.50 cm (0.59") 3 3.56 cm (1.40") 2.34 cm (0.92") 2.21 cm (0.87") 4 3.56 cm (1.40") 4.17 cm (1.64") 1.83 cm (0.72") 2.24 cm (0.88") 1.88 cm (0.74") 2.13 cm (0.84") Average 3.51 cm (1.38") 3.30 cm (1.30") 2.06 cm (0.81") Soft 3-jaw, 9mm, Zinc-core shells Test # BBL # 1 BBL # 2 BBL # 3 1 6.12 cm (2.41") 4.90 c (1.93") 2.49 cm (0.98") 2 5.94 cm (2.34") 3.30 cm (1.30") 3.94 cm (1.55") 3 3.30 cm (1.30") 3.12 cm (1.23") 4.37 cm (1.72") 4 2.08 cm (0.82") 3.51 cm (1.38") 2.69 cm (1.06") 3.86 cm (1.52") 3.40 cm (1.34") 3.58 cm (1.41") Average 4.27 cm (1.68") 3.66 cm (1.44") 3.40 cm (1.34") BBL = test barrel for Luger 9 mm.

The rebound potential was evaluated by firing five essentially pure tin core projectiles and five core-zinc projectiles into a blank of the 0.635.cm (one-quarter inch) mild steel plate that has a Brinnel hardness of between 55 and 60 HB. The target was placed at 15.24 m (50 feet) on the front of a 9-millimeter Luger test barrel at a zero-degree runoff angle. Table 3 records the results of the impacts between the projectile and the target.

TABLE 3 * BJ = Shirt of the Bullet. * '= distance in feet It is evident that a lead-free projectile which completely satisfies the objects, meanings and advantages described hereinabove has been provided according to the present invention. Although the invention has been described in combination with the embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art - in light of the foregoing description. Accordingly, it is proposed that it encompass all such alternatives, modifications and variations that are considered within the spirit and broad scope of the appended claims.

It is noted that in relation to this date, the best method known by the applicant to carry out the aforementioned invention, is the conventional one for the manufacture of the objects to which it relates.

Having described the invention as above, property is claimed as contained in the following

Claims (14)

1. A lead-free projectile, characterized in that it comprises: a. metal jacket having an outer surface defining an aerofoil and an internal surface defining at least one cavity; and the at least one cavity is filled with essentially pure tin having an elastic limit of less than 20 MPa.

2. A lead-free projectile, characterized by an essentially pure tin body that has an elastic limit of less than 20 MPa and shaped with an aerodynamic profile.

3. The lead-free projectile according to claims 1 or 2, characterized in that the essentially pure tin has a maximum of 0.5% by weight, of the total alloy formation additions and a maximum of 0.25%, by weight, of any addition for the formation of the alloy.

4. The lead-free projectile according to claim 2, characterized in that the essentially pure tin has a maximum of 0.2% by weight, of the additions for the total alloy formation and a maximum of 0.1%, by weight, of any addition for the formation of the alloy.

5. The lead-free projectile according to claim 4, characterized in that the maximum zinc content of essentially pure tin is less than 0.005%, by weight.

6. The lead-free projectile according to claim 5, characterized in that the essentially pure tin contains at least 99.85%, by weight, of tin and, by weight, a maximum of 0.04% of antimony, a maximum of 0.05% of arsenic, a maximum of 0.030% bismuth, a maximum of 0.001% of cadmium, a maximum of 0.04% of copper, a maximum of 0.015% of iron, a maximum of 0.05% of lead, a maximum of 0.01% of sulfur, and a maximum of 0.01% (nickel + cobalt).

7. A lead-free projectile, characterized in that it comprises: a metal jacket having an outer surface defining an aerofoil and an internal surface defining at least one cavity; and the at least one cavity that is filled with a tin-based alloy containing magnesium and having an elastic limit of less than 20 MPa.

8. The lead-free projectile according to claim 7, characterized in that the magnesium is present in an amount from about 0.5% to 5%, by weight, and other additions for the formation of the alloy are present in a total amount of less than 0.5%, by weight.

9. The lead-free projectile according to any of claims 1, 7 or 8, characterized in that the metal jacket is formed of a metal selected from the group consisting of copper, aluminum, copper alloys, aluminum alloys and steel.

10. The lead-free projectile according to claim 9, characterized in that the metal jacket is formed of a copper-zinc alloy.

11. The lead-free projectile according to claim 9, characterized in that the projectile is effective to be fired from a gun.

12. The lead-free projectile according to claim 9, characterized in that the projectile is effective to be fired from a rifle.

13. The lead-free projectile according to claim 9, characterized in that the metal jacket has a centrally located fragmentation portion separating a rear cavity and a front cavity with the essentially pure tin which is contained within both the rear cavity and the cavity lead.

14. The lead-free projectile according to claims 1, 7 or 8, characterized by at least one cup-shaped insert placed in at least one cavity between the essentially pure tin and the portion of the nose.