Ammunition and explosives – Projectiles – Composite
Patent
1995-09-26
1998-02-17
Jordan, Charles T.
Ammunition and explosives
Projectiles
Composite
102501, 102529, 102448, 102455, F42B 3000
Patent
active
057193525
DESCRIPTION:
BRIEF SUMMARY
This invention relates to shot pellets and the like.
Many thousands of tonnes of lead pellets are scattered on the surface of the earth and embedded in trees and fences each year in the act of bird, clay pigeon and small game shooting for business or pleasure. It is now recognised that where this shot falls on wetlands it may be taken up by many birds in the belief that it can become part of the normal complement of pebbles or gravel that performs an essential duty in the crops of these birds. Unfortunately, the outcome can be that the birds suffer from progressive lead poisoning which can result in their death or, equally disturbing, their value as human food becomes very suspect. A further problem now recognised is that lead may be dissolved from the deposited shot and enter into the structure of crops grown for human food. A similar problem with the gathering up of lead fishing weights by swans seems to have been resolved by the adoption of alternative heavy materials for making the weights. Attempts to apply a similar solution to the shot used in making shotgun cartridges have proved much more difficult because of the stringent requirements imposed on the physical properties of the shot by the severe conditions that they are exposed to in the firing of the guns.
A key property of lead that makes it so successful as a shot material is its high density, 11.35 tonnes per m.sup.3, because the energy associated with the shot at the moment that it strikes its target relates to its mass and its velocity as E=1/2 mv.sup.2. Lead has a modest position in the list of abundancies of the metallic elements at 10 parts per million and poses no problem of dwindling resource. Iron has been proposed as an alternative and has found some use but its density is only 7.86 tonnes per m.sup.3 which means that it only has 69.25% of the striking energy provided by lead shot of the same size. Iron shot also offers problems because of its rigidity which can damage the bores of costly sporting guns and even be hazardous when used in certain types of guns because of the development of abnormally high and dangerous pressures. The softness of lead allows it to negotiate safely the bores of guns which are choked at the barrel end to modify the pattern of the flying shot. Steel shot can also give problems by its tendency to corrode and this process can bind the loose shot in a typical cartridge into solid slugs which can damage the gun. It is also reported to give difficulties in timber growing areas where the shot is embedded in tree trunks and presents a hazard to power driven woodsaws. Shot made of highly elastic metals, such as steel, also poses a hazard to participants and onlookers because it is far more prone to ricochet from hard surfaces than malleable lead shot.
Bismuth has also been proposed as a shot material because it has a density of 9.747 tonnes per m.sup.3 which is higher than iron at 7.68 tonnes per m.sup.3, but its abundance is much lower than lead 0.004 parts per million and it is a secondary metallurgical material that is to say a by-product of the refining of other metals. This means that its source is precarious and the price, already high, could escalate if attempts were made to adopt it generally. Bismuth also suffers from being a very weak and brittle metal and can only be made into a useable shot if it is alloyed with expensive tin or toxic lead. There are also unresolved questions about the possible toxicity of bismuth when ingested by animals.
It is an object of the present invention to provide an improved shot material which avoids the above-noted disadvantages of lead and is also free of the cost penalty, brittleness and possible toxicity of bismuth.
According to one aspect of the invention, there is provided a shot formed of a material comprising finely divided metallic particles in a polymer matrix.
The material from which the shot is formed may comprise a mixture of finely divided particles of molybdenum and tungsten in a polymer matrix.
According to another aspect of the invention there is provided a
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Chelliah Meena
Jordan Charles T.
Silverman Arnold B.
The Kent Cartridge Manufacturing Co. Limited
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