WO2012140628A1

WO2012140628A1 - Bullet

Info

Publication number: WO2012140628A1
Application number: PCT/IB2012/051869
Authority: WO
Inventors: Floyd MORRISON; Nico PIENAAR
Original assignee: Tri-Blade Innovations Cc
Priority date: 2011-04-15
Filing date: 2012-04-16
Publication date: 2012-10-18
Also published as: ZA201308193B

Abstract

The invention concerns a bullet (10) for use with a firearm. The bullet includes an elongate body (12) which has a maximum diameter which corresponds substantially to a groove diameter of a barrel (100) of the firearm from which the bullet is intended to be fired. The bullet (10) further has a front portion (12.1), a rear portion (12.2) and a substantially cylindrical central portion (14) located between the front and rear portions. A bearing area (16) is provided substantially in the central portion (14) of the body and a major portion of the bearing area is threaded. The tread forms a continuous spiral groove (17) along a major portion of the surface of the bearing area in order to reduce the amount of material through which the rifling (102) of the barrel (100) has to cut when the bullet (10) is fired from the firearm.

Description

BULLET"

BACKGROUND TO THE INVENTION

This invention relates to a bullet. Particularly, but not exclusively, the invention relates to a monolithic bullet for use with a firearm.

It is well known that a barrel of a firearm, such as a rifle, has spiral formations or grooves, also commonly referred to as rifling, on its inside surface in order to increase the accuracy of the flight of the bullet when fired from the rifle. The rifling grooves spin the bullet when fired in order to stabilise it in flight. Due to the rifling cutting into the bullet as it travels along the barrel a considerable portion of the energy produced by the propellant inside the bullet casing is wasted through friction. The wasted energy is converted into heat instead of kinetic energy used to propel the bullet and, as a result, the velocity at which the bullet is fired is reduced. In order to compensate for the loss of bullet velocity the pressure inside the barrel is- increased. The increase in barrel pressure in turn results in a reduced barrel life. The dimensions of the bullet relative to the barrel are critical in ensuring that an appropriate bullet velocity is reached upon firing. Bullets are generally designed so that the diameter of the body of the bullet corresponds to a groove diameter of the barrel. It should be understood that the barrel of the rifle has two diameters, namely a groove diameter which is the major diameter and a bore diameter which is the minor diameter. By using a bullet which has a body diameter which corresponds to the groove diameter of the barrel, there is sufficient friction between the bullet and the barrel for the pressure inside the barrel to reach a required level so that the bullet may be fired at the desired velocity.

A known method of reducing the friction between the bullet and the barrel is to cut a number of annular grooves into the body of the bullet. Although it is generally held that such a bullet performs better than conventional bullets which does not have grooves, it is believed that the friction produced by a grooved bullet inside the barrel can be reduced even further. There are also other disadvantages associated with these prior art bullets. For example, the manufacturing process of the grooved bullet is cumbersome in that each groove must be cut into the body of the bullet individually. This process is time-consuming and obviously has cost implications.

Molybdenum disulphide is also often applied to bullets as a coating to reduce fouling and friction in the barrel. The molybdenum disulphide is normally applied to the body of a bullet prior to the body being inserted into its casing. Another problem associated with existing bullets is that a substantial amount of the molybdenum disulphide is removed from the bullet during the loading process in which the bullet is inserted into its casing,, thus reducing the amount of .lubricant available in the barrel upon firing.

It is an object of this invention to alleviate at least some of the problems experienced with existing bullets. It is a further object of this invention to provide a bullet that will be a useful alternative to existing bullets.

SUMMARY OF THE INVENTION

According to the invention there is a bullet for use with a firearm, the bullet including:

an elongate body having a maximum diameter which corresponds substantially to a groove diameter of a barrel of the firearm from which the bullet is intended to be fired,

a front portion, a rear portion and a substantially cylindrical central portion located between the front and rear portions; and

a bearing area provided substantially in the central portion of the body, wherein a major portion of the bearing area is threaded so as to form a continuous spiral groove along a major portion of the surface of the bearing area.

The threaded area may be dimensioned so that the thread major diameter corresponds substantially to the groove diameter of the barrel and the thread minor diameter corresponds substantially to the bore diameter of the barrel of the firearm.

The thread pitch is preferably between about 0.1 mm and about 1 mm, while the thread depth is preferably between about 0.1 mm and about 1 mm and the thread angle is preferably between about 55 and about 60 degrees.

The bullet may include two annular recesses located on either side of the threaded area so as to form a front recess and a rear recess, wherein the diameter of the body of the bullet at each recess may be less than the maximum diameter of the body of the bullet. The diameter of the body of the bullet at the front and rear recesses may be substantially equal to the bore diameter of the barrel of the firearm.

The bullet may further include a bearing seal surface which has a diameter which corresponds substantially to the maximum diameter of the body of the bullet and which may be located between a rear end of the bullet and the rear recess.

The bullet is preferably a monolithic bullet.

The front portion of the body may be in the shape of an ogive while the rear portion may be in the shape of a boat-tail.

The bullet may also be a hollow point bullet.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings in which:

Figure 1 shows a perspective view a bullet according to the invention;

Figure 2 sows a side view of the bullet of Figure 1 ;

Figure 3 shows a cross-sectional side view of the bullet of Figure 1 ;

Figure 4 shows a cross-sectional view of the bullet of Figure 1 in a casing; and

Figure 5 shows s cross-sectional view of the bullet and casing of

Figure 4 loaded in a chamber of a firearm. DESCRIPTION OF THE ILLUSTRATED EMBODIMENT

Figure 1 shows a side view of a bullet 10 according to the invention. The bullet has an elongate body 12 which has a maximum diameter which corresponds substantially to a groove diameter of a barrel 00 of a firearm from which the bullet is intended to be fired. As mentioned above the groove diameter of the barrel is the major diameter while the bore diameter is the minor diameter.

Although it is envisaged that the bullet 10 may find particular application for use with a rifle, particularly in the hunting industry, it must be understood that it may be used with any firearm and is not limited to use with a rifle. In the description of the illustrated embodiment the bullet 10 will be described with reference to a rifle by way of example only.

In the preferred embodiment the bullet 10 is a monolithic bullet and the body 12 has a front portion 12.1 and a rear portion 12.2. It should be understood that the front and rear portions are labelled with reference to the direction in which the bullet is intended to be fired. The front portion 12.1 is in the shape of an ogive for aerodynamic purposes while the rear portion 12.2 is boat-tailed. As can be seen in the figures the ogively shaped front portion is substantially flat at the front and increases in diameter towards the rear of the bullet. In the preferred embodiment the maximum dimension of the front portion 12.1 corresponds substantially to the maximum diameter of the body 12 and accordingly the groove diameter of the barrel of the rifle.

The bullet 10 further has a central portion 14 which is substantially cylindrically shaped and located between the front and rear portions. The central portion 14 includes a bearing area 16 which has a maximum diameter which corresponds substantially to the groove diameter of the barrel of the rifle. It must be understood that the size of the bearing area 16 is dependent on the shape of the ogive 12.1 seeing that the shape will determine the extent to which the body 12 will be in contact with rifling 102 of the barrel 100 when the bullet 10 is fired from the rifle.

At least a major portion of the bearing area 16 is threaded so as to form a continuous spiral groove 17 along the surface of the bearing area. The thread 17 is dimensioned so that a major diameter 18.1 of the thread corresponds substantially to the groove diameter of the barrel while a minor diameter 18.2 of the thread corresponds substantially to the bore diameter of the barrel of the rifle from which the bullet is intended to be fired. The dimensions are illustrated in Figure 3 of the drawings.

It is envisaged that the thread pitch may be between about 0.1 mm to about 1 mm, while the thread depth may be between about 0.1 mm and about 1 mm. It is further envisaged that the thread angle may be between about 55 and 60 degrees.

It can be seen from Figure 2 that the bullet 10 includes two annular recesses 20.1 and 20.2 located on either side of the threaded area 17 so as to form a front recess and a rear recess. At each of the recesses 20.1 and 20.2 the body 12 has a reduced diameter which is less than its maximum diameter and, accordingly, the groove diameter of the barrel. In the preferred embodiment of the bullet 10 the front and rear recess diameters are substantially equal to or less than the bore diameter of the barrel of the rifle.

The body 12 further includes a bearing seal surface 22 which is located in the bearing area 16 and between the rear portion 12.2 and the rear recess 20.2. The bearing area seal surface 22 has a diameter which corresponds substantially to the maximum diameter of the body so that in use there is an interference fit between the surface 22 and the barrel of the rifle. In use the bearing seal surface 22 acts as the final seal between the body and the barrel when the bullet is fired by the rifle. Now turning to Figure 3 it can be seen the illustrated bullet 10 is a hollow point bullet in that it has a bore 24 extending into the body of the bullet from its front end.

Figure 4 shows the bullet 10 mounted in its casing 26 while Figure 5 shows the bullet and casing loaded in the rifle chamber 104 ready to be fired. When the bullet 10 is fired from the rifle, the rifling 102 inside the barrel 100 starts to engrave into the bullet ogive 12.1 towards the front recess 18.1 which is located at the end of the ogive. The fouling material produced by the rifling cutting into the ogive 12.1 is collected in the front recess 20.1. It should be clear to a person skilled in the art that the advantage of collecting the fouling material in the recess is that friction between the body 12 and the barrel 100 is reduced. As the bullet 10 moves along the barrel the rifling starts to cut into the threaded bearing area 16. Due to the major portion of the bearing area being threaded the amount of material through which the rifling 102 has to cut is reduced considerably, thereby reducing the amount of friction between the body 12 of the bullet and the barrel 100. Again, the excess fouling material is collected in the rear recess 20.2 located next to the threaded area 17, thereby reducing the friction between the body 12 of the bullet and the barrel 100. Finally the rifling 102 cuts into the bearing area seal surface 22 as the bullet travels along the barrel. As a result of the boat-tail end portion 12.2 the fouling material produced by the rifling cutting into the bearing seal surface 22 are allowed to drop-off at the rear of the body.

It must be understood that an advantage of the threaded bearing area 16 is that the thread may be machined into the body using a single, continuous process. The fine pitch of the thread of the bearing area 16 also allows for better seating of the bullet in its casing 26 as shown in Figure 4 as opposed to bullets including annular grooves.

In the case of molybdenum disulphide coated bullets being used, an advantage of the bullet 10 according to the invention, and in particular the threaded bearing area 16, is that less of the molybdenum disulphide coating is removed during the loading process in which the body is inserted into its casing 26. This ensures that more of the coating on the body 12 of the bullet 10 is available as lubrication when travelling through the barrel, thus reducing fouling and friction even further.

It is believed that in addition to a decrease in friction between the body 12 and the barrel 100 and the improved accuracy, the bullet 10 according to the invention will also cause the life of the barrel to be extended. The extended barrel life is largely due to the fact that a reduced barrel pressure can be used to achieve the desired bullet velocity.

Claims

C LAI MS

1. A bullet for use with a firearm, the bullet including:

2. A bullet according to claim 1 , wherein the threaded area is dimensioned so that the thread major diameter corresponds substantially to the groove diameter of the barrel and the thread minor diameter corresponds substantially to the bore diameter of the barrel of the firearm.

3. A bullet according to either claim 1 or 2, wherein the thread pitch is between about 0.1 mm and about 1 mm.

4. A bullet according to any one of the preceding claims, wherein the thread depth is between about 0.1 mm and about mm.

5. A bullet according to any one of the preceding claims, wherein the thread angle is between about 55 and about 60 degrees.

6. A bullet according to any one of the preceding claims, including two annular recesses located on either side of the threaded area so as to form a front recess and a rear recess, wherein the diameter of the body of the bullet at each recess is less than the maximum diameter of the body of the bullet.

7. A bullet according to claim 6, wherein the diameter of the body of the bullet at the front and rear recesses is substantially equal to the bore diameter of the barrel of the firearm.

8. A bullet according to either claim 6 or 7, including a bearing seal surface which has a diameter which corresponds substantially to the maximum diameter of the body of the bullet and which is located between a rear end of the bullet and the rear recess.

9. A bullet according to any one of the preceding claims, wherein the bullet is a monolithic bullet, and wherein the front portion of the body is in the shape of an ogive and the rear portion is in the shape of a boat-tail.

10. A bullet according to any one of claims 1 to 9, wherein the bullet is a hollow point bullet.