Ammunition and explosives – Projectiles – Target marking
Reexamination Certificate
1999-02-23
2002-04-30
Nelson, Peter A. (Department: 3641)
Ammunition and explosives
Projectiles
Target marking
Reexamination Certificate
active
06378439
ABSTRACT:
The present invention relates to a marker projectile and to the combination of a marker projectile and a cartridge.
BACKGROUND
Marker projectiles for use in training or war games are well known and examples of such projectiles are disclosed in U.S. Pat. No. 4,686,905, GB 2 284 252, GB 1 263 522, U.S. Pat. No. 3,528,662, U.S. Pat. No. 4,128,059 and U.S. Pat. No. 3,782,286.
Most of the aforementioned patents disclose projectiles in which a marker substance is held within a frangible casing or enclosure which ruptures upon impact with a target. A problem with projectiles such as bullets that are intended to break upon impact is that sometimes they fail to break. Moreover, because of the high impact required to break the frangible casing or enclosure, the projectiles can often cause injury upon impact with a person. A further problem is that the frangible casings or enclosures can sometimes break in a gun during the gun's reloading cycle.
Some of the aforementioned problems are addressed in GB 2 284 252 which discloses a projectile comprising a hollow casing having a perforated nose portion, a piston disposed within the casing, and a marking substance disposed forwardly of the piston. The piston is movable forwardly under force applied to it by gas used to discharge the projectile thereby compressing the marking substance and expelling it through the nose portion which thus becomes coated with the marking substance. Upon impact with a target, the marking substance is transferred to the target to mark the target.
However, a problem with projectiles, such as those disclosed in GB 2 284 252, in which the nose portion of the projectile is coated with a marking substance even before the projectile has left the gun barrel, is that the marking substance is dispersed by the rotation imparted to the projectile by the rifling in the gun barrel. Thus, the centrifugal force imparted by the spinning bullet causes the marking substance to move radially outwardly and consequently it can foul the barrel of the gun. A build up of marking substance, or its thermal decomposition products, in the gun barrel over time will inevitably have an adverse effect on the working of the gun. This problem is greatly exacerbated with bullets designed for use in high velocity rifles such as the NATO and U.S. 5.56 mm calibre rifles where the rifling in the barrel must be such as to impart a very high spin rate to the bullet in order to ensure a stable trajectory. Even with relatively low velocity training ammunition, the high spin rates imparted by the rifling in high velocity rifles are still sufficient to cause the marking substance to disperse in the manner described above.
A still further problem with the marker projectile of GB 2 284 252 and other known marker projectiles is that they are unsuitable for small calibre barrels such as the current NATO and U.S. 5.56 mm calibre self loading rifle barrels. This is not only because of the problem of radial dispersion of the marking substance referred to above, but also because the complexity of the bullet poses considerable manufacturing difficulties with smaller calibre bullets.
SUMMARY OF THE INVENTION
It is an object of the invention to provide a marker projectile which overcomes or at least substantially alleviates the aforementioned problems.
The solution provided by the present invention is to provide an arrangement in which an expelling member such as a steel ball is held within the projectile interior behind the marking substance such that upon impact and arrest of the movement of the outer casing of the projectile, the momentum of the expelling member carries it forward relative to the outer casing to expel the marking substance through the front of the projectile.
Accordingly, in a first aspect, the invention provides a marker projectile comprising a hollow body having an opening at the front; a marker substance disposed within the hollow body; and an expelling member within the hollow body behind the marking substance; characterised in that the hollow body and expelling member are configured such that upon impact of the projectile with a target, the momentum of the expelling member relative to the hollow body carries the expelling member forwardly to expel the marking substance through the opening.
Thus, in the marker projectile of the invention, it is the momentum of the expelling member within the hollow body of the projectile which carries it forwardly after impact of the projectile with the target so as to force the marking substance out of the opening in the front of the projectile, This feature distinguishes the projectile of the invention from known projectiles such as those disclosed in GB 2 284 252 where a piston within the projectile is driven forwardly by the propellant gases in the cartridge or gun to expel the marker substance.
In the projectiles of the invention, the expelling member is insulated from the propellant gases; in other words, the propellant gases do not act on the expelling member to force it forwardly to cause expulsion of the marking substance.
In one embodiment, the hollow body comprises a sleeve having a core body portion secured within a rear end thereof, the inner wall of the sleeve and a forwardly facing surface of the core body portion defining a chamber within which the marking substance and expelling member are disposed. The sleeve typically has a cylindrical form, a spigot portion of the core body member being received (preferably non-slidably) within the rear end of the sleeve. The sleeve is preferably formed from a material having a greater density than the material from which the core body portion is formed. Thus, for example, the sleeve can be formed from a metal material such as aluminium and the core body portion can be formed from a plastics material. The advantage of this feature is that (with the exception of the expelling member) the mass of the hollow body is concentrated towards its outer circumference which improves its ballistic qualities.
It is most preferred that the hollow body is provided with means for centring the expelling member therein during flight of the projectile. By providing centring means, lateral movement of the expelling member during flight is prevented and the destabilising effect of such movement is therefore avoided. The centring means can be a recess in a forwardly facing surface within the interior of the hollow body. Where the hollow body comprises a core body portion and a sleeve, the centring means can comprise a recess in the forwardly facing surface of the core body portion. The recess constituting the centring means can be conical, frustoconical, hemispherical or part hemispherical, for example.
The expelling member can take a variety of shapes provided that it is rotationally symmetrical about its longitudinal axis. Preferably it is of a spherical shape and more preferably it is a solid sphere.
The expelling member is typically formed from a material having a greater density than the materials) from which the hollow body is formed. Thus, for example, the expelling member can be formed from steel. Where the projectile comprises a sleeve and core body portion, it is preferred that the expelling member has a greater density than the sleeve and the core body portion. It will appreciated also that, typically, the expelling member will have a density greater than the density of the marking substance.
In order to ensure that the expelling member can be carried forwardly by its own momentum within the hollow body upon impact with a target without its motion being retarded by frictional engagement with an inner surface of the hollow body, there is preferably a radial clearance between the centred expelling member and the inner wall of the hollow body (e.g. sleeve) sleeve.
In the projectiles of the invention, the motivating force urging the expelling member forwardly against the marking substance is the expelling member's own momentum. There is no need for a piston/cylinder arrangement driven by the expanding propellant gases within the gun barrel upon firing. On the cont
Lahive & Cockfield LLP
Nelson Peter A.
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