WO2000066967A1

WO2000066967A1 - Shot cartridge and wad

Info

Publication number: WO2000066967A1
Application number: PCT/SE2000/000502
Authority: WO
Inventors: Christer Holmgren
Original assignee: Christer Holmgren
Priority date: 1999-05-04
Filing date: 2000-03-14
Publication date: 2000-11-09
Also published as: SE9901610D0; AU3852600A

Abstract

A shot cartridge for smooth barrel shot guns, comprising a cartridge (5), a girdle (51) having a firing cap (52), a powder charge (53), and a cup or wad (55) for holding a cluster of shots (54) passing through the barrel on firing, wherein a radial compressible volume (57) extends axially through the cluster of shots.

Description

SHOT CARTRIDGE AND WAD

The present invention relates to improvements in ammunition for smooth barrel shotguns in accordance with the preamble of claim 1.

The invention specifically, but not exclusively, relates to improvements in ammunition designed for steel shots.

In the course of finding alternatives to lead shots, several problems arise in respect of effective impact energy, wear on the barrel bore and accelerating gas pressures and loads on firing cartridges having hard shots of lower density than lead. Suggested alternatives to lead shots may include shots of steel, steel alloys, hard metal compounds comprising tungsten carbide, bismuth, e.g., copper and copper alloys, synthetic material compounds, etc.

Due to the lower specific weight, these alternatives will usually have to be fired at higher velocities to provide a killing effect on impact at practical shooting ranges in hunting. Due to an increased hardness in relation to lead, they may also produce substantial wear on the barrel bore if exposed to surface contact during passage thereof. Also, increased mechanical loads on the barrel have been notified, eventually causing dangerous barrel eruptions in weapons not specifically designed for this ammunition.

As a result, many existing weapons designed for ammunition comprising lead shots may prove not to be reliable for use in combination with ammunition having shots of alternative and lead free materials.

A problem in connection with hunting is related to the lower specific weight of steel shots. In European Common market countries, security standards prescribe for cal. 12 cartridges a maximum muzzle velocity of 400m/sec at V_2t5l maximum muzzle load of 12 Ns, maximum gas pressure of 740 bar Piezo and maximum shot size of 3,25 mm (US No. 4). When one of these parameters is exceeded in a cal. 12 shot cartridge, the cartridge may be fired exclusively in weapons which are tested and approved for so called High Efficiency cartridges.

The killing effect of the lower efficiency cartridge according to these standards is greatly affected. To secure effective impact, shooting ranges have to be shortened. Additionally, the spread of shots in the target is less, likewise calling for shorter ranges and accurate hits.

The present invention aims to provide a shot cartridge which may be charged with steel shots for practical hunting, with shot sizes above 3,25 mm but still not generating hazardous mechanical loads and gas pressures in a standard weapon.

A technical problem to be solved by the present invention is therefore to provide a shotgun ammunition, designed to balance or to lower the radial mechanical load generated upon firing shot cartridges having shots of alternative, lead free materials, e.g. steel shots.

It is contemplated, that deformation, and eventually eruption, of a shotgun barrel on firing cartridges comprising steel shots or shots of comparative hard materials, are caused by peak gas pressures and radial mechanical loads building up in the chamber as the shots pass the conical entrance to the cylindrical bore. Due to the increased hardness of the shots, these will not deform as willingly as shots of lead. Excessive pressure is therefore generated abruptly, causing a radial chock load in the conical exit area of the chamber, as the cluster of tightly held shots hit the internal wall of the conical area more or less like a homogenous projectile.

It is therefore an object of this invention to provide a shot cartridge designed to balance and to lower such chock loads produced as the cluster of shots are squeezed through the conical area connecting the cartridge chamber and the cylindrical barrel bore.

Further it is contemplated, that increased wear on the barrel bore, and significantly referred to the conical mouth of the chamber and in choked bores, is caused by the hard material shots in surface contact with the bore as a result of the holding cup being demolished by the radial mechanical loads, when the cluster of shots pass the conical areas.

It is therefore another object of this invention to provide a shot cartridge designed to reduce the radial mechanical loads, thereby avoiding a demolition of the cup which is holding the cluster of shots on passage through the barrel bore. These and other objects are met in a shot cartridge according to the preamble of claim 1 , modified to comprise the features of the characterising part thereof. Preferred embodiments of the inventive shot cartridge are found in the sub-claims.

Briefly, the invention provides a shot cartridge comprising a powder charge, a firing cap and a cluster of shots accommodated in a cylindrical cup or a wad, wherein a radial compressible volume extends axially through the cluster of shots. The wad with a radial compressible volume may be designed in various ways, as will be seen from the following disclosure, and may preferably be defined in a hollow member which is integrally formed with the cup to rise axially from the centre of the cup bottom like a tube shaped cylinder.

The invention is described more in detail below, reference being made to the attached drawings wherein

Fig. 1 is a longitudinal section view showing a shot cartridge of the invention according to a first and preferred embodiment, inserted in the cartridge chamber of a partly broken away shotgun barrel;

Figs. 2a to 2d are sectional views showing embodiments of the invention;

Figs. 3a to 3b are longitudinal sections showing further embodiments of the invention, and

Figs. 3c to 3d are elevation views showing yet further embodiments of the invention.

Referring to fig. 1 , a shotgun barrel 1 is shown with a part thereof being broken away to show the smooth-bored passage from a chamber 2, through a cylinder section 3 to a nozzle 4. A shot cartridge 5, as will be described more in detail below, is seated in the chamber 2 and in firing position. The cylinder section 3 opens into the chamber 2 by a conical transition section 6, and into the muzzle by a slightly conical choke bore 7. The choke 7 may be optionally formed in the barrel, and may also be applied as a detachable and exchangeable unit for controlling the spread of shots in flight towards a target. The chamber 2 is machined to have very small deviations from a nominal dimension, characteristic for a specific gun calibre, whereas the inner sectional width of the cylinder section 3 may vary as much as 0.7 mm in shot guns of different origin and production. The conical section 6, connecting the chamber and the cylinder section 3 of the barrel, may vary in length from about 10 to about 50 mm, and is in the average shot gun barrel about 25 mm in length. The wider inner section A of the conical section 6 is normally about 20.3 mm in width, in a 12 cal. shotgun. The narrower section B, i.e. the entrance to the cylinder section 3, is normally (nominal dimensions) about 18.4 mm (Europe) and about 18.6 mm (U.S.). In cal. 12 shot guns, the bore may have a sectional width within the range of about 18.2 to 18.9 mm.

In dependence of the sectional width of the cylinder section 3 and the length of the conical section 6, a contraction in the cluster of shots upon passage through the conical section 6 will occur at varying time lengths, and at varying mechanical, radial loads. A peak gas pressure is generated as the cluster of shots is forced through the conical section 6, and accordingly the maximum gas pressure is related to the length and radial contraction of the conical section 6.

When the individual shots are soft enough to deform during passage of the conical section 6, individual specifications in shot guns of different production will still produce allowable and secure gas pressures on firing. However, the steel shots or similar hard shots other than lead may produce excessive gas pressures that may cause an eruption of the gun barrel on firing. It is contemplated, that excessive gas pressures are rising to a peak as the cluster of harder metal shots are forced to contract upon passage through the conical section 6. In the case of hard shots, less willing to deform, excessive mechanical radial loads and deformations have been notified in, and near to, the conical sections.

The shot cartridge 5 according to the invention comprises a cylinder cartridge 50, one end thereof inserted in a metallic girdle 51 with a firing cap 52 applied in the centre of its back-plane. A powder charge 53 is accommodated in the girdle 51 , and a cluster of shots 54 is loaded in a cylinder cup or wad 55, placed in front of the powder charge towards the muzzle end of the barrel. The shot cartridge 5 is shown in the drawing with its front end 56 closed, as it will be before firing, and may conventionally be produced from a synthetic material or impregnated cardboard material. The wad 55 is commonly produced from a synthetic material.

In the conventional cartridge, charged with shots of lead, the cluster of shots normally occupies a limited space at the front end of the cylinder cartridge which allows the wad to be formed with pressure balancing and reducing means in the cup bottom. In case of shots having lower specific weight than lead, the cluster of shots provides little axial space for pressure reducing means on the cup. This may also be contemplated to contribute to the accelerating gas pressures produced upon firing steel shot charged cartridges.

Returning to the cartridge 5 of fig. 1 , the cluster of shots 54 is shown with a columnar body 57 extended axially through the cluster of shots. The columnar body 57 may be realised in various ways, as will be seen in the following disclosure of preferred embodiments of the invention.

The columnar body 57 provides a radial compressible volume of the wad, having a capacity to accommodate radial pressure exerted by the wall of the barrel bore as the cluster of shots 54 passes there-through, in order to reduce or substantially to eliminate the risk of barrel eruption.

The radial mechanical load is accelerated to a maximum as the cluster of shots 54 passes the conical section 6, and the conical mouth of the choke bore 7. In a cartridge charged with steel shots or other shots of similar hard metal, the radial load from the conical section 6 and choke bore 7 may cause demolition of the cup holding the shots. Due to the hardness of the steel shots, exaggerated wear may occur on the bore if the cup brakes, and the shots are allowed to contact the surface thereof, on passage through the bore.

Thus, the columnar body 57 also reduces radial mechanical loads to rescue the cup and to essentially reduce or substantially to eliminate the risk of surface contact between the shots and the barrel bore. The columnar body 57, i.e. the radial compressible volume 57, may be constructed in various ways. Referring to figs. 2a to 2d, different embodiments of the radial compressible volume 57 are shown in sectional views along the line 11-11 of fig. 1.

Fig. 2a shows the circular section of a radial compressible volume 57, comprising a hollow cylinder.

Fig. 2b shows the polygonal section of a radial compressible volume 57, comprising a hollow, multisided body.

Fig. 2c shows the star shaped section of a radial compressible volume 57, comprising a hollow body having concave sides connected by longitudinal ribs.

Fig. 2d shows the section of a radial compressible volume 57, comprising a hollow body having convex sides connected by longitudinal grooves.

Alternatively, the radial compressible volume 57 may also comprise a homogeneous, deforming body of cellular material, see fig. 3a, or a deforming body made of fibrous synthetic or nature material as illustrated in fig. 3b, or a deforming body which is formed by slitting and expanding an element of synthetic material as illustrated in figs. 3c and 3d.

Presently preferred, however, the radial compressible volume 57 is formed by a yielding, hollow cylinder of synthetic material, extending axially through the cluster of shots from the bottom centre of a cup where the cylinder is attached, and preferably integrally formed with the cup.

The radial compressible volume 57 according to the invention is yielding from the radial pressure by the surrounding shots on passage through the bore, and may have flexible properties as well.

It is considered not be necessary to dimension the radial compressible volume 57 to fully compensate for the radial contraction in the barrel bore. It is contemplated, rather, that a radial compressible volume 57 of a maximum sectional width up to approximately 8 mm would suffice, to balance the radial contraction to an extent where hazardous chock loads and radial mechanical loads may be substantially reduced to allowable levels. In combination with a cartridge of the type having a rolled end closure, at least, sufficient space for an operative charge of shots will always be available.

Further it is considered, that the radial compressible volume 57 extended axially through the cluster of shots may advantageously effect the spread of shots for efficient hits in practical hunting. The ballistics of steel shots, e.g., display conventionally a more straight trajectory than shots of lead. This is partly explained by differences in deformation properties, whereby the shot of steel is a more perfect sphere also after firing. In the inventive cartridge, the radial compressible volume 57 may provide a central guide in the cluster of shots leaving the muzzle, providing in hunting a desired spread of shots at effective shooting ranges.

Thus, there is provided a new shot cartridge and wad for steel shots or shots of other material than lead, designed for reducing radial mechanical loads and for balancing peak gas pressures so as to make possible a charge for practical hunting also in use with the average and common shotgun.

Claims

1. A shot cartridge for smooth barrel shot guns, comprising a cartridge (5), a girdle (51) having a firing cap (52), a powder charge (53), and a cup (55) for holding a cluster of shots (54) passing through the barrel on firing, characterised by a radial compressible volume (57) extended axially through the cluster of shots for accommodating radial contraction of the cluster of shots, and thereby reducing radial mechanical loads exerted on the barrel bore upon passage there-through.

2. A shot cartridge according to claim 1 , characterised by the radial compressible volume being defined in a yielding, hollow member.

3. A shot cartridge according to claim 1 , characterised by the radial compressible volume being defined in a yielding member produced of a cellular material.

4. A shot cartridge according to claim 1 , characterised by the radial compressible volume being defined in a yielding member produced of a fibrous synthetic or nature material.

5. A shot cartridge according to claim 2, characterised by the radial compressible volume being defined in a yielding member which is integrally formed with the cup.

6. A shot cartridge according to claim 5, characterised by the radial compressible volume being defined in a tube shaped, yielding cylindrical member extending axially from the cup (55) bottom centre.

7. A shot cartridge according to claim 1 , characterised by the radial compressible volume having a cylinder cross section, or a polygonal cross section, or a star-shaped cross section having concave sides, or a cross section having convex sides.

8. A shot cartridge according to any of previous claims, characterised by a radial compressible body having flexible properties.

9. A shot cartridge according to any of previous claims, being charged with shots of other metals or metal compounds than lead.

10. A wad for a shot cartridge, characterised by a radial compressible volume (57) extended axially through the cluster of shots contained in the cup-shaped wad (55).