WO2004090464A1

WO2004090464A1 - Medium density bronze shot

Info

Publication number: WO2004090464A1
Application number: PCT/CA2004/000503
Authority: WO
Inventors: Kenneth H. Elliott
Original assignee: International Non-Toxic Composites Corporation
Priority date: 2003-04-07
Filing date: 2004-04-01
Publication date: 2004-10-21

Abstract

The present invention is directed to medium density shot for shotgun cartridges and to shotgun cartridges comprising the medium density shot. The shot consists essentially of bronze, the bronze being a copper/tin alloy or a copper/silicon alloy having a density in a range of from about 8.2-9 g/cc. Such shot is particularly useful for sport hunting of small animals, for example birds, particularly waterfowl, such as, for example, ducks, geese and the like.

Description

MEDIUM DENSITY BRONZE SHOT

This application claims the benefit of United States Patent Application 60/460,396 filed April 7, 2003.

Field of the Invention

The present invention relates to medium density shot for shotgun cartridges.

Background of the Invention

Lead has been used in a variety of industrial applications for many thousands of years. In the last hundred years, the toxic effects of lead ingestion on humans, and wildlife in general, have become apparent. Throughout the world various environmental agencies classify the metal and many lead compounds, including oxides, as Hazardous Wastes. As an example, in the USA, about 51% of lead solid waste, has in the past, been due to spent ammunition and ordinance. Lead shot used for hunting waterfowl is now prohibited because of its toxicity to birds that are wounded but not killed and to wildlife that ingest loose shot. Firing of small arms ammunition for training, sporting, law enforcement and military purposes contributes a significant potential for environmental pollution and constitutes a human health risk. In the USA the Department of Energy, (DOE), expends about 10 million rounds of small arms ammunition each year, resulting in a deposit of over 100 tonnes of lead. The DOE's use of ammunition is small compared with that of civilians, law enforcement agencies and the Department of Defence. Overall, it is estimated that in the USA, hundreds of tonnes of lead are released into the environment every day. In the early 1980's the use of lead in shot was strictly regulated for sport hunting. Since then there has been intensive research into non-toxic replacements for lead. However, very few alternatives to lead have come to market due to poor performance, toxicity issues of their own and/or cost of production.

Due to the toxicity and environmental concerns surrounding lead, steel shot has largely replaced lead as the shot used in shotgun cartridges. However, steel shot has a number of problems making it less than ideal for use in shotgun cartridges. For example, steel shot is much harder than lead, thus its use in shotguns can cause damage to the barrels. Given its hardness, special precautions and specifically designed loading components must be used for cartridges loaded with steel shot to prevent damage to barrels. In addition, there are several older makes of quality shotguns which are not steel compatible. In addition, steel shot has a density of no greater than about 7.8 g/cc, thus steel shot is particularly prone to wind drift making it less effective, especially over longer distances.

Various metal composites containing copper have been developed with a view to replacing lead in shot. However, these copper-containing alternatives have been too low in density to be an effective replacement. Additionally, these copper-containing alternatives suffer from unacceptable levels of copper dissolution in water, which prevents the shot from being approved by government regulatory agencies due to the toxicity of copper. The same toxicity problem is true for pure copper shot.

Bronze has been used to make frangible bullets. For example, U.S. Patent 6,074,454 issued June 13, 2000 to Delta Frangible Ammunition LLC discloses a frangible bullet made of bronze (90:10 Cu:Sn) using Acrawax™ as a lubricant and sintered at a temperature of 1500-1600°F. United States Patents 6,090,178 and 6,263,798 issued July 18, 2000 and July 24, 2001 respectively, to SinterFire Inc. disclose frangible bullets made of bronze (90:10 Cu:Sn) with zinc stearate lubricant and debound at 260°C.

There remains a need for a medium density shot for shotguns, which has a good balance between density, hardness, toxicity and cost. Summary of the Invention

In a first aspect of the invention, there is provided shot for shotgun cartridges, the shot consisting essentially of bronze, the bronze being a copper/tin alloy or a copper/silicon alloy having a density in a range of from 8.2-9 g/cc.

In a second aspect of the invention, there is provided shot for shotgun cartridges, the shot consisting essentially of bronze, the bronze being a copper/tin alloy nominally having about 85-95% by weight copper and about 5-15% by weight tin based on the weight of the bronze, and the bronze having a density in a range of from about 8.2-9 g/cc.

In a third aspect of the invention, there is provided shot for shotgun cartridges, the shot consisting essentially of bronze, the bronze being a copper/siiicon alloy nominally having 97-99% by weight copper and 1-3% by weight silicon based on weight of the bronze, and the bronze having a density in a range of from 8.2-9 g/cc.

In a fourth aspect of the invention, there is provided a shotgun cartridge comprising a casing, a primer, a propellant, and shot, the shot consisting essentially of bronze, the bronze being a copper/tin alloy or a copper/silicon alloy.

In a fifth aspect of the invention, there is provided a shotgun cartridge comprising a casing, a primer, a propellant, and shot, the shot consisting essentially of bronze, the bronze being a copper/tin alloy nominally having about 85-95% by weight copper and about 5-15% by weight tin based on the weight of the bronze, and the bronze having a density in a range of from about 8.2-9 g/cc.

In a sixth aspect of the invention, there is provided a shotgun cartridge comprising a casing, a primer, a propellant, and shot, the shot consisting essentially of bronze, the bronze being a copper/silicon alloy nominally having 97- 99% by weight copper and 1-3% by weight silicon based on weight of the bronze, and the bronze having a density in a range of from 8.2-9 g/cc. Brief Description of the Drawings

The invention will now be described by way of non-limiting example with reference to the following drawings, wherein:

Figure 1 is a graph of downrange pellet velocity (fps) versus range (yds) comparing the ballistics performance of bronze shot to steel shot for 1450 fps loads;

Figure 2 is a graph of downrange pellet velocity (fps) versus range (yds) comparing the ballistics performance of bronze shot to steel shot for 1265 fps loads;

Figure 3 is a graph of downrange pellet energy (ft-lbs) versus range (yds) comparing the ballistics performance of bronze shot to steel shot for 1450 fps loads;

Figure 4 is a graph of downrange pellet energy (ft-lbs) versus range (yds) comparing the ballistics performance of bronze shot to steel shot for 1265 fps loads.

Detailed Description

As used in the specification and the appended claims, the singular forms "a," "an" and "the" include plural referents unless the context clearly dictates otherwise.

Ranges may be expressed herein as from "about" or "approximately" one particular value and/or to "about" or "approximately" another particular value. When such a range is expressed, another embodiment includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent "about," it will be understood that the particular value forms another embodiment. Composition:

Bronze is a term used to describe any alloy of copper containing at least 78% by weight copper. In the context of the present invention, bronze specifically refers to copper/tin alloys or copper/silicon alloys.

Bronzes consisting essentially of a copper/tin alloy nominally having about

85-95% by weight copper based on the weight of the bronze are particularly noteworthy. Bronzes nominally having about 88-93%, or about 89-91 %, or about 90% by weight copper may be specifically mentioned. The tin component of the copper/tin alloy may be nominally present in an amount of about 5-15%, or about 7-12%, or about 9-11 %, or about 10% by weight based on the weight of the bronze.

Bronzes consisting essentially of a copper/silicon alloy nominally having about 97-99% by weight copper based on the weight of the bronze are particularly noteworthy. Bronzes nominally having about 97-98%, or about 97% by weight copper may be specifically mentioned. The silicon component of the copper/silicon alloy may be nominally present in an amount of about 1-3%, or about 2-3%, or about 3% by weight based on the weight of the bronze.

Other elements and/or compounds may be present in the bronze in any amount, which does not sacrifice the desired properties of the bronze.

For example, bronzes consisting essentially of copper/tin alloy may also contain nickel, lead, zinc, iron, phosphorus, aluminum, antimony, silicon, sulfur, manganese, magnesium, bismuth, lithium compounds, mixtures thereof, etc. Generally, other elements or compounds collectively make up about 2% by weight or less of the total weight of the copper/tin bronze. Any individual other element or compound will generally be present in an amount of about 1 % by weight or less, usually 0.5% by weight or less. The presence of other elements and/or compounds may impart further desirable properties, for example, silicon could impart corrosion resistance to the copper/tin bronze. For example, bronzes consisting essentially of copper/silicon alloy may also contain tin, nickel, lead, zinc, iron, phosphorus, aluminum, antimony, sulfur, manganese, magnesium, bismuth, mixtures thereof, etc. Generally, other elements or compounds collectively make up about 5% by weight or less of the total weight of the copper/silicon bronze. Any individual other element or compound will generally be present in an amount of about 2% by weight or less, usually 1.5% by weight or less. The presence of other elements and/or compounds may impart further desirable properties to the copper/silicon bronze.

The density of the bronze, and therefore of shot made from the bronze, is desirably in a range of from about 8.2-9 g/cc. Densities in a range of from about 8.5-9 g/cc, or about 8.8-8.9 g/cc may be mentioned specifically. Densities in these ranges provide good ballistic performanc.e for the shot. For example, bronze shot will suffer from significantly less wind drift than steel shot.

Suitable bronzes may be purchased commercially from any number of suppliers. Some specific examples of bronzes are:

Bronze C52400 from Anchor Bronze & Metals, Inc. nominally having 90 wt% Cu, 10 wt% Sn and 0.35 wt% P with small amounts of Pb, Fe and Zn;

Bronze C521 from Fisk Alloy Wire, Inc. nominally having 91.8 wt% Cu, 8.0 wt% Sn and 0.2 wt% P with small amounts of Pb, Fe and Zn;

Bronze C510 from Fisk Alloy Wire, Inc. nominally having 5% Sn, 0.2% P and balance Cu with small amounts of Pb, Fe and Zn; and

Phosphor Bronze 524 from Anaconda nominally having 89.75% Cu, 10.00% Sn and 0.25% P.

Everdur 655 from Aufhauser Corporation nominally having 3 wt% Si and remainder Cu with small amounts of Zn, Sn, Mn, Fe, Al and Pb.

C65500 High Silicon Bronze A from Anchor Bronze and Metals, Inc. nominally having 97 wt% Cu and 3 wt% Si with small amounts of Pb, Fe, Zn, Mn and Ni. Process:

Suitable bronzes may be purchased in the form of wires, sheets, strips, blocks, ingots, etc. Any suitable process to produce bronze pellets may be used. For example, known processes for producing ball bearings and existing processes for producing steel shot may be used in the production of bronze shot pellets. It is well within the ability of one skilled in the art to adapt these known or existing processes, without undue experimentation, to the production of bronze shot.

Some suitable processes include, for example, heading, roll forming, die cutting, moulding, casting, shot tower techniques, etc. Heading or roll-forming techniques, either cold or warm but preferably cold, are more rapid than casting or moulding and are better suited to the manufacture of shot, since high throughput is required to make the process more economical. For the production of shot, a wire, strip or sheet of bronze may be stamped or rolled out to give substantially spherical bronze particles. For example, the bronze, in the form of a wire, strip or sheet, may be stamped progressively using a series or an array of punches to form regular indentations until the spherical bronze particles are finally stamped out. Alternatively, spinning rolls with a dimpled texture may be used to form the spherical bronze particles from a sheet of bronze. The substantially spherical bronze particles may then be finished to produce shot. No sintering of the bronze shot so produced is required nor generally desired.

In a particularly suitable process, bronze wire is cold forged into substantially spherical particles by cutting the wire into pieces of desired sized and then forming the pieces into substantially spherical particles between forming dies using a heading machine. The substantially spherical particles are then subjected to rough deflashing to remove the flash line (a ridge left by the forming dies) by rolling or grinding the particles between heavy plates or grinding wheels. The heavy plates or grinding wheels may be cast iron or any other suitable material. The resulting shot pellets are substantially spherical in shape and may be used as is or, optionally, further descaled, ground and/or finished. Descaling is a process whereby residues and by-products of the preceding steps are removed from the spherical pellets. The shot pellets may be further ground in a hard grinding step to ensure proper sizing and sphericity. Finally, the shot pellets may be finished, for example, by polishing in mechanical and/or chemical polishing processes.

Use:

Shot of the present invention can be used in any shotgun cartridge. Since the shot has a medium density, it is particularly useful in shotgun cartridges intended for use on small game, particularly for birds, for example, waterfowl, pheasants, pigeons, doves, etc. The non-toxic characteristic of the shot of the present invention makes the shot excellent for use in cartridges intended for waterfowl, for example ducks, geese, and the like.

The construction of a shotgun cartridge is well known to one skilled in the art and does not need to be elaborated in detail. The book Reloading for Shotgunners by Kurt D. Fackler and M.L. McPherson (4^th Edition, Krause Publications, 1998, particularly page 9) provides an overview of shotgun cartridge construction and loading. A shotgun cartridge typically comprises a casing, a primer, a propellant and shot pellets. In addition, a wad may be used to separate the shot pellets from the propellant. A wad typically comprises a shot cup and a gas seal. The casing typically comprises a hull attached to a base. One end of the base is closed except for a primer pocket into which the primer is inserted. After insertion of the primer, the propellant, for example gun powder, is then loaded into the base and the wad is then loaded over top of the propellant. The gas seal of the wad seals the propellant in the base. Shot pellets are then loaded into the shot cup of the wad. The hull is then crimped at the end to hold the shot pellets, wad and propellant inside the casing. The shot cup typically extends up just short of the top of the hull to fill the volume of the hull. The base of the casing is typically a cylinder made of any suitable material, for example brass, steel or plastic. The hull of the casing is typically a flexible tube and may comprise any suitable material, for example paper or a plastic (e.g. high-density polyethylene). Wads may comprise any suitable material, for example plastic or a fibrous material (e.g. paper). The bronze shot of the present invention is advantageous for a number of reasons. Some of these reasons are as follows. The bronze shot has a density greater than steel thus contributing to better ballistic performance than steel shot currently sold in the market place. Despite the copper content of the bronze shot, copper dissolution in water and acid is surprisingly low, which will likely lead to its acceptance by government regulatory bodies such as the U.S. Fish and Wildlife Agency. The bronze shot is cost effective to make, not requiring retooling of existing plants and it can be sold profitably at a price point less than or equivalent to steel shot. The bronze shot is not as hard as steel shot, therefore reducing or eliminating damage to shotguns, particularly the barrels.

Examples

Example 1: Production of Bronze Shot

C52400 annealed bronze wire (from Anchor Bronze & Metals, Inc.) having a wire gauge of 9/64 inch, nominally having 90 wt% Cu and 10 wt% Sn, and having a density of 8.9 g/cc, is chopped into pieces 9/64 inch in length and cold headed into substantially spherical particles between the dies of a heading machine. The substantially spherical particles are deflashed in a grinder (from Noonan Machine Company) to form substantially spherical bronze pellets having a density of 8.9 g/cc. If desired, the substantially spherical bronze pellets may then be hard ground with a grinder (Noonan Ball Machine from Noonan Machine Company) to produce bronze pellets of more exact dimensions and then dry polished in a polishing drum.

Example 2: Hardness Comparison

The hardness of bronze was compared to the hardness of six comparative examples using the Rockwell F hardness scale. The results are shown in Table 1 below. The following samples were compared: Bronze: C52400 annealed bronze of Example 1 having a density of 8.9 g/cc.

Comp. 1 : Nitro™ Steel Shot from Remington Arms. Nitro™ Steel Shot has a density of about 7.8 g/cc.

Comp 2: Hevi-shot™ from Remington Arms. This is a sintered W/Ni/Fe composite having a density of 12.0 g/cc.

Comp. 3: An annealed tungsten bronze composite, nominally having 52 wt% tungsten and 48 wt% bronze and having a density of 11.3 g/cc.

Comp. 4: A hardened tungsten bronze composite, nominally having 52 wt% tungsten and 48 wt% bronze and having a density of 11.3 g/cc.

Comp. 5: An annealed tungsten bronze composite, nominally having 52 wt% tungsten, 47.2 wt% bronze and 0.8 wt% iron and having a density of 11.8 g/cc.

Comp. 6: A hardened tungsten bronze composite, nominally having 52 wt% tungsten, 47.2 wt% bronze and 0.8 wt% iron and having a density of 11.8 g/cc.

Table 1

It is apparent from Table 1 that bronze is significantly less hard than all of the other samples tested, including steel shot currently being sold in the marketplace. Despite being of medium density, bronze is less hard than both the high density alternatives (Comp. 2-6) and the lower density steel shot (Comp. 1 ). Example 3: Ballistics Comparison

The downrange ballistics performance of bronze shot was compared to that of steel shot using standard ballistics calculations. The calculated results are shown in Table 2 below. The data in Table 2 is presented in graphical form in Figures 1-4. It is evident from Table 2 and Figures 1-4 that bronze shot outperforms steel shot in maintaining downrange pellet velocity and downrange pellet energy for a given pellet size and/or initial velocity (load) over a range of downrange distances.

It will be understood that certain features and sub-combinations are of utility and may be employed without reference to other features and sub-combinations. This is contemplated by and is within the scope of the claims.

Since many possible embodiments may be made of the invention without departing from the scope thereof, it is to be understood that all matter herein, set forth or shown in the accompanying drawings is to be interpreted as illustrative and not in a limiting sense.

Table 2

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Claims

CLAIMS:

1. Shot for shotgun cartridges, the shot consisting essentially of bronze, the bronze being a copper/tin alloy or a copper/silicon alloy having a density in a range of from 8.2-9 g/cc.

2. Shot for shotgun cartridges, the shot consisting essentially of bronze, the bronze being a copper/tin alloy nominally having 85-95% by weight copper and 5- 15% by weight tin based on weight of the bronze, and the bronze having a density in a range of from 8.2-9 g/cc.

3. Shot according to claim 2, wherein the copper/tin alloy nominally has 88-93 wt% copper and 7-12 wt% tin.

4. Shot according to claim 2, wherein the copper/tin alloy nominally has 89-91 wt% copper and 9-11 wt% tin.

5. Shot according to claim 2, wherein the copper/tin alloy nominally has 90 wt% copper and 10 wt% tin.

6. Shot according to any one of claims 2 to 5, wherein the density is in a range from 8.5-9 g/cc.

7. Shot according to any one of claims 2 to 5, wherein the density is in a range from 8.8-8.9 g/cc.

8. Shot according to any one of claims 2 to 7, wherein the bronze further contains nickel, lead, zinc, iron, phosphorus, aluminum, antimony, silicon, sulfur, manganese, magnesium, bismuth, lithium compounds or a mixture thereof.

9. Shot according to claim 6, wherein the nickel, lead, zinc, iron, phosphorus, aluminum, antimony, silicon, sulfur, manganese, magnesium, bismuth, lithium compounds, or mixture thereof is present collectively in an amount no greater than 2 wt% based on the weight of the bronze.

10. Shot according to claim 8 or 9, wherein any one of the nickel, lead, zinc, iron, phosphorus, aluminum, antimony, silicon, sulfur, manganese, magnesium, bismuth or lithium compounds is present in an amount no greater than 1 wt% based on the weight of the bronze.

11. Shot according to claim 8 or 9, wherein any one of the nickel, lead, zinc, iron, phosphorus, aluminum, antimony, silicon, sulfur, manganese, magnesium, bismuth or lithium compounds is present in an amount no greater than 0.5 wt% based on the weight of the bronze.

12. Shot for shotgun cartridges, the shot consisting essentially of bronze, the bronze being a copper/silicon alloy nominally having 97-99% by weight copper and 1-3% by weight silicon based on weight of the bronze, and the bronze having a density in a range of from 8.2-9 g/cc.

13. Shot according to claim 12, wherein the copper/silicon alloy nominally has 97-98 wt% copper and 2-3 wt% silicon.

14. Shot according to claim 12, wherein the copper/silicon alloy nominally has 97 wt% copper and 3 wt% silicon.

15. Shot according to any one of claims 12 to 14, wherein the density is in a range from 8.5-9 g/cc.

16. Shot according to any one of claims 12 to 14, wherein the density is in a range from 8.8-8.9 g/cc.

17. Shot according to any one of claims 12 to 16, wherein the bronze further contains tin, nickel, lead, zinc, iron, phosphorus, aluminum, antimony, sulfur, manganese, magnesium, bismuth or a mixture thereof.

18. Shot according to claim 17, wherein the tin, nickel, lead, zinc, iron, phosphorus, aluminum, antimony, sulfur, manganese, magnesium, bismuth or mixture thereof is present collectively in an amount no greater than 5 wt% based on the weight of the bronze.

19. Shot according to claim 17 or 18, wherein any one of the tin, nickel, lead, zinc, iron, phosphorus, aluminum, antimony, sulfur, manganese, magnesium or bismuth is present in an amount no greater than 2 wt% based on the weight of the bronze.

20. Shot according to claim 17 or 18, wherein any one of the tin, nickel, lead, zinc, iron, phosphorus, aluminum, antimony, silicon, sulfur, manganese, magnesium or bismuth is present in an amount no greater than 1.5 wt% based on the weight of the bronze.

21. A shotgun cartridge comprising a casing, a primer, a propellant, and shot according to any one of claims 1 -20.

22. The shotgun cartridge according to claim 21 , further comprising a wad in the casing between the propellant and the shot.