GB2502507A - Projectile holder for multiple projectiles - Google Patents

Abstract

A projectile holder (e.g. sabot) includes a body portion having a central axis and a plurality of alcoves. Each alcove is adapted to house a projectile. The plurality of alcoves are linearly aligned relative to each other in a direction corresponding to the central longitudinal axis. At least one of the alcoves is laterally and/or radially offset relative to another of the alcoves.

Description

Sabot for use in conjunction with a rifled barrel A discarding sabot which holds multiple projectiles, for use in conjunction with a rifled barrel that allows the simultaneous firing of multiple gyroscopically stabilized sub calibre projectiles to form a spread of shot across a target where each shot is fired to a specific predestined position within that pattern.

Background to the design

There are many advantages of a weapon that simultaneously fires a number of projectiles in a spread of shot across a target over one that fires a single shot. There is a greatly increased probability of hitting the target, multiple hits on a target can increase the lethality and the time taken to aim at the target is greatly reduced so you can not only hit a target quicker but additionally engage targets that are seen far more briefly.

The prior art methods of simultaneously firing a number of projectiles to form a pattern of shot are as follows.

Firstly to use a smoothbore barrel as found on various weapons from a pistol or shoulder fired shotgun up to a tank barrel and ammunition containing normally spherical shot or flachettes which although provides a good spread of shot has it's limitations in terms of the shot pattern and the projectiles fired.

The pattern of shot fired from smooth bored barrels is known as a bellmouth or Gaussian pattern (sometimes known as a normal pattern). The distribution of projectiles being dense in the centre of the pattern then tapering off at the edges often with voids in the pattern where there are no projectiles. Though the individual projectiles trajectory's are quite random the overall pattern can be reasonably consistent and there is some ability to alter the pattern by using for instance using different wadding designs, barrel lengths and chokes.

The smoothbore barrel does not impart spin to the projectiles it fires which means they are not gyroscopically stabilized in flight not only making them less accurate and more easily blown off target by wind but also limiting there shape to either spherical ball known as shot, drag stabilized slugs or flachettes. Spherical ball and drag stabilised slugs can be very effective for hunting and military use on soft targets but have very high drag and so loose energy very quickly giving them a very short range and rapid bullet drop which can make accurate shooting difficult. Flachettes which although have very little drag and a very long effective range are only normally used on armoured targets as they over penetrate soft targets and have little of what is termed knock down power.

Secondly there have been traditional rifle cartridges made to fire multiple projectiles through a rifled barrel without using a sabot, however the space available in the rifle cartridges to add extra projectiles limited the projectile number normally to two and the inability to offset the projectile within the barrel limited the nature of the shot pattern these factors reducing there benefit over a single projectile round to such an extent that there was little real advantage to the invention over using a single projectile cartridge combined with a higher rate of fire.

Thirdly a shotgun cartridge with traditional prior art wadding which fires multiple bullets or disc shaped projectiles through a rifled barrel where they are held centrally in the bore. The projectiles either all having the same approximate point of impart, or relying on imperfections in manufacture, being disturbed during release or aerodynamic buffeting to randomly form the shot pattern.

Summary of the invention

The invention allows multiple projectiles to be fifed simultaneously through a rifled barrel to form a pattern of shot. With the advantage of being able to gyroscopically stabilize the projectiles, meaning it can not only fire spherical ball more accurately but if the projectiles are positions close enough to the longitudinal centre of the bore within the sabot also provide enough spin to fire ogive and spitzer shaped bullets which give the projectiles a far greater effective and accurate range.

Additionally the invention allows each projectile to be fired to a specific pre designed place within the shot pattern and so is not limited to a Gaussian pattern or even a circular pattern, it eliminates the random nature of the shot pattern and the chance of voids within it as well as allowing a more effective pattern to be designed.

A further advantage of the rifled barred weapon designed to fire the invention is that it will be able to more accurately fire single projectile ammunition than a smoothbore shotgun.

The invention fulfils the same functions as a prior art sabot for a rifled barrel of providing a consistent gas seal to prevent any propellant gases escaping past the sabot, engaging the rifling to impart spin to the sabot and on to the sub calibre projectiles contained within and holding the projectiles in there intended positions within the barrel.

However where the invention differs is that instead of holding a single projectile that is smaller than the bore of the barrel as precisely as possible in the centre of the bore to make each shot as accurate as possible. The invention holds multiple sub calibre projectiles within it that can be off set from the centre of the bore about its longitudinal axis.

When the ammunition is fired, those projectiles that are held by the invention in positions that are off set from the longitudinal axis of the centre of the barrel. Travel down the rifled barrel in a helical path till the invention leaves the barrel and discards the projectiles, the off set projectiles each then veer away from the trajectory they would have taken if held centrally in the bore, to form the desired pattern of shot being no longer restrained within the invention by the barrel of the rifle. The amount each projectile veers away from the trajectory of a projectile held precisely in the centre of the bore, is governed by four factors. The mass of the projectile. The velocity of the projectile. The distance from the centre of the longitudinal axis of the bore it was located within the invention. The rate of the rifling twist.

These factors can be manipulated to control the angle the trajectory an off set projectile takes from that of one fired from a position in the centre to the bore. An increase in the mass, velocity, distance from the longitudinal axis of the bore or the rifling twist would all increase the size of the angle to the trajectory of an offset projectile would take from one held centrally in the bore.

Introduction to the drawings

Figure 1. A cross section through the main embodiment illustrated in a shotgun cartridge and containing projectiles.

Figure 2. Shows the position of the projectiles inside figure 1, looking at the front open end of the embodiment towards the base.

Figure 3. Shows a side view of the main embodiment of the invention.

Figure 4. Shows an end view of the main embodiment looking at the front end of the invention.

Figure 5. Shows the same embodiment as figure 3 without the projectiles and rotated through 45 degrees.

Figure 6. Shows the same embodiment as figure 2 without the projectiles and rotated through 45 degrees.

Figure 7. Shows a section through figure 5 in a position shown in figure 6.

Figure 8. Shows a section through figure 5 in the position shown in figure 5.

Figure 9. Shows a section through figure 11 in the position shown in figure 11.

Figure 10. Shows a section through figure 11 in the position shown in figure 11.

Figure 11. Shows a section view similar to figure 1 through an alternative embodiment that illustrates a number of additional features.

Figure 12. Shows a section view through one finger or petal of an alternative embodiment of the invention showing additional features.

Figure 13. Shows a finger or petal of the invention from the same view as figure 4 showing an additional feature and the position of figure 12, Figure 14. Shows a cross section through an alternative embodiment of the invention from the same view as in figure 1.

Figure 15. Shows a cross section of the same embodiment as in figure 14 without being contained within a cartridge.

Figure 16. Shows the base or cup portion as shown in figure 15 looking at the front down towards it's base.

Figure 17. Shows a shot pattern for the main embodiment.

Figure 18. Shows an alternative shot pattern for the main embodiment.

Figure 19. Shows a cross section of an alternative embodiment illustrated in an alternative cartridge type and containing projectiles.

Figure 20. Shows a side view of the alternative embodiment in figure 19.

Figure 21. Shows the embodiment in figure 20, beginning to open.

Detailed description

In figure 1, 1 shows a cross section through the centre of a one piece discarding sabot containing five projectiles each held individually within the invention, located in this embodiment in 4 an 89mm, 12 gauge shotgun cartridge with a roll crimped front, meeting a lip on the front of the invention 10, to push against the shell case to open it when fired. This embodiment of the invention being made of separate sections but formed in one single piece, having the advantages of comparatively cheap production and following a similar initial path to the projectiles when fired, rather than flying off in different directions possibly hitting bystanders.

The invention consisting of a base section 12 and four side sections 13 which are known as petals or fingers. All the sections that are in contact with the barrel swage to fit, imparting spin to the invention.

The base section 12 providing the gas seal and supporting the base of the projectile immediately in front. The fingers 13 hold the projectiles in position until it has left the barrel, the two forces of inertia caused by the inventions rotation and drag then forcing the petals or fingers 13 of the invention to open.

The petals or fingers 13, of the sabot narrow where they join the base 12, this forms a type of hinge at 3. inducing bending at this point. The sabot fingers 13 bending back until either side of the cut away section 2 between the base 12 and the fingers 13 meet, holding them open in that position to give greater drag than if the fmgers opened completely folding back on them selves. This angle can be altered to suit how far you wish the petals of the invention to open before being held in that position as figure 12 item 22, the angle of the cut away section can also be changed to increase the contact patch between the base and petals to support them better in the held open position.

The gap that runs centrally along the length of the invention linking all the projectile positions II, allows it to be formed in the closed position as well as with the petals or fingers open. Depending on which method of manufacture is used the thickness and rigidity of the material at position 3 of the invention, can be critical to the design.

It's ability to resist the forces trying to open the fingers of the invention being one way of controlling when the invention opens and releases it's projectiles. This opening point being critical.

When the invention first exits the barrel the expanding gases that where held behind the invention, are then free to blast past it. If the invention opens to early these gases will disturb the opening petals or fingers of the invention preventing the clean release of the projectiles. Additionally when the invention first leaves the barrel the pressure behind the invention is momcntarily higher then the pressure in front causing the invention to carry on accelerating even though it has left the barrel. If it began to release the projectiles before it stopped accelerating the invention would be unable to release the projectiles cleanly, as the projectiles rclcased first would collide with those released momentarily later.

There are ways of reducing the effects of the gases escaping past the invention and the higher initial pressure behind it without altering the invention. Changing the propellant bum rate, using a longer barrel or porting the barrel can reduce the effects.

The longer it takes for the invention to release the projectiles after it has left the barrel, the more of the projectiles energy will be wasted, as the invention containing them travels through the air less efficiently that the individual projectiles.

The longer it is before the projectiles are released the greater the chance of yaw in the invention which would effect the shot pattern and individual projectiles.

The optimum release point is the earliest point where the projectiles can be released cleanly without disturbance. Firing the invention through a shorter barrel than the cartridge containing it is designed to be used from could not only disturb the release of the projectiles but also give a smaller shot pattern due to the lower velocity.

The petals or fingers of the invention 13 are formed to support around the sides of the projectiles 5,6, 7, 8 and 9 with the shape of the invention immediately in front and behind the projectiles formed to ensure there clean release without disturbing there position within the shot pattern. Clean projectile release is more important in the invention than in traditional single projectile shotgun cartridge sabots, as the mass of the individual projectiles is so much smaller, they can more easily be knocked off there designed trajectory by the sabot.

The projectiles 5, 6, 7, 8 and 9 being lubricated to aid that clean release. The boat tailed shape of the projectiles 5, 6, 7, 8 and 9 spreading the pressure on the invention at the base of each projectile meaning less material is required to support the base, reducing the size of the gap between each projectile thereby allowing longer projectiles to be used. The invention holding the projectiles 5, 6, 7, 8 and 9 in position and providing the gas seal means the projectiles do not need to fulfil these functions, so don't need to have long straight sides to engage with the barrel.

From this view you can see that the offset projectiles 6,7,8 and 9 do not point parallel to the longitudinal axis of the bore, to reduce the effects of yaw in these projectiles they are held in positions within the invention pointing toward the direction they will be fired in, not parallel to the bore.

As figure 1 shows the projectiles are all positioned along the centre line of the sabot, this limits the number and length of the projectiles you can fit in the cartridge unlike in a prior art shotgun cartridge where the projectiles can be stacked along side each other. This is because the further a projectile is positioned away from the centre of the longitudinal axis of the bore within the invention the less stabilizing spin is imparted to it from the rifling. The full benefits of the invention would only be available on tighter patterns. To compensate projectiles requiring different twist rates can be used in the same sabot. If a wide spread is required, this would mean that little stabilizing spin would be imparted to the projectiles.

However as shown in figure 19 spherical ball 29 could still be used, retaining the benefit over prior art ammunition of greater flexibility and accuracy of the shot pattern. Wide patterns normally being used at short range mean the rapid loss of velocity experienced with spherical ball would be less of an issue and more projectiles would fit in the same length invention.

The timing of the projectiles 5, 6, 7, 8 and 9 release is an important consideration in the design of the invention. If the projectiles 5, 6, 7, 8 and 9 are all released simultaneously there is the chance that they will collide in flight before there flight paths diverge sufficiently for them to avoid collision. The first projectile 5, slowing down due to friction with the air more than the ones behind 6, 7, 8 and 9. The wider the pattern however the less chance there is of collision. A slight increase in the gap after the first projectile in the invention may be all that is required to prevent collision.

There are ways to reduce the amount the fir st projectile is slowed down compared with the ones behind it. Firstly by reducing the effect of friction with air on the first projectile, by making it a more ballisticlly efficient shape or from a heavier material.

Secondly by increasing the effects of drag on the projectiles behind it by using boat tailed projectiles that disturb the air flow less and putting projectiles with a smaller cross sectional area in front than those behind. The projectiles position win the invention can be used to put greater space between those on similar trajectories.

There is also a slight disruptive effect to the projectiles 6, 7, 8 and 9 caused by them going from the dirty or turbulent air behind the projectile in front and breaking out into clean air with laminar flow, which could effect the accuracy and increase yaw.

These effects can be greatly reduced by very slightly increasing the air gap between the projectiles in flight, this could be done by fractionally delaying the release of each projectile after the one in front by allowing slight flex in the fingers of the invention as they open, this bowing effect would release the projectiles at the front earlier.

As the invention would still be rotating in flight even a slight delay between releasing the projectiles would alter the shape of the shot pattern if not allowed for and corrected. If the alteration to the pattern was great enough to require a correction.

In figure 2. Shows the position of the projectiles 5, 6, 7, 8 and 9 in the invention as you would see them if looking from the front of the invention 20 down to the base 13.

It shows the mass of the projectiles within the invention balanced about the centre, which is the centre of the longitudinal axis of the barrel. This stops any wobble experienced by firing an unbalanced mass in a helical path down the barrel, which could disturb the position of the barrel whilst firing.

In figure 3. You see a external view of figure 1, the invention being a light weight plastic sabot, cylindrical in appearance being of one piece construction. It shows the shape of the cutaway sections 2, where the inventions petals or fingers 13, join to the base 12. It shows the position of the lip 10 on the front of the invention 20 that pushes open the crimped section of the cartridge when fired and is used as the point to crimp down to.

In figure 4. This shows the four separate fingers 13 of the embodiment to be of equal size. This helps ensure the fingers all open at the same rate, the more equal there size and mass the more equal the effects of inertia and drag upon them. The off set projectiles are positioned with there centre of mass in thejoin between two fingers of the invention to aid there clean release as the invention opens. The smaller the number of fingers the stronger they are, giving them a greater ability to resist opening, the more controlled there opening and the less they could be twisted out of shape when first engaging the rifling. This figure 4 shows no gap between the fingers of this embodiment, the fingers touching support each other as they first engage the rifling. An embodiment with a larger number of projectiles may require a larger number of fingers to release the projectiles cleanly.

In figure 5 you see once again the base 12 fingers 13 and the cut away portions of the invention as in figure 3 rotated through forty five degrees and showing the position of figure 8.

In figure 6 you see the front of figure 5 showing position of the figure 7.

In figure 7 you see a cut away view of figure 5 in the position shown. The additional feature of this embodiment is a protrusion 14 going from one finger 13 into a socket designed to fit it, in the next. This feature is designed to control the opening of the invention till the desired point after leaving the barrel, by offering resistance to the forces of inertia and drag trying to open it, causing a momentary delay. After leaving the barrel the forces quickly exceeding the protrusions 14 limits of resistance, it then deforms allowing the invention to open. This feature being damaged in use would make the embodiment non reusable, this could be an advantage in military use.

In figure 8 you see the feature shown in figure 7 to be used as a set of four one going from each of the fingers 8 of the invention into the next linking them all together.

Although only one set is shown the embodiment may require additional sets running the length of the invention to properly control the opening as required.

In figures 9. Is the cross sectional view of the embodiment in figure 11 above it's base. The view shows that unlike other embodiments the fingers of the embodiment do not touch along there sides. The view shows the fmgers to be joined at this point by a thin area of material designed to stiffen up the fingers of the embodiment resisting the forces trying to open out the fingers, thereby delaying it opening. The thin areas shown at 15 being designed to break in use, the fingers then bending back in the same way as the embodiment in figure 1.

In figure 10. Is a cross section view through a circular plastic ring 19 shown to fit a recess made for it on the front of the embodiment shown in figure 11.

Two features of the ring are firstly four cuts 17 in the ring designed to leave a specific thickness of material left, so a specific force will break the ring allowing the fingers to open. The cuts in the ring should be deeper than the cuts made by the rifling of the barrel, so the ring would need to be of sufficient thickness to allow this. The cuts can change depth along the length of the ring so that if the ring is sufficiently long it could offer increased resistance to opening, the further the fingers 13 opened. The four rectangular features 16 on the inside of the ring are made to fit the gap in between the fingers 13 to strengthen them against the twisting action they encounter when they first engage the rifling.

In figure Il. There is a cross section through a three piece discarding sabot containing five projectiles each held individually within the invention, made to fit in an 89mm, 12 gauge shotgun cartridge with a roll crimped front. This embodiment shows fingers that do not meet along there sides a gap 21 shown. This embodiment is made to include two additional features to control the opening of the embodiment.

Firstly additional material 15 joining the bottom of the fingers 13.

The material joining the fingers 15 being at the rear of the embodiment it has the ability to allow the front to begin to open flexing the sides before it breaks and the full length of the fingers open releasing all the projectiles 5, 6, 7, 8 and 9.

This feature means that to form the position of the last projectile in the embodiment and fit the projectile into it,a portion of the base 20 of the embodiment is separate and fitted once the projectile has been put into position.

Secondly a plastic ring 19 to fit over the outside of the embodiment as shown in figure 10. Although the ring in figure 10 is shown to fit the front of the invention in figure 11 it is not limited to this position. The lip 10 on the front of the embodiment in figure 1 is on the ring in this embodiment. These features may not appear on the same embodiment but instead act as separate methods to achieve the same effect.

In figures 12 and 13. Voids in the invention 24 are shown running down the sides of the sabot fingers 13 that perform two functions, firstly reducing the overall mass of the sabot slightly reducing recoil and secondly reducing the mass of the individual petals or fingers 13, this reduces the force of inertia acting upon them to open caused by there rotation. The lighter the petals the less they are forced open. The voids can also be used to reduce the rigidity of the petals causing them to flex slightly as they open.

In figure 12. A separate obturating disc 23 is shown at the base; this would allow the main sabot to be re used making the invention more affordable.

In figure 14. Is shown an embodiment of the invention which is a discarding sabot of two piece construction containing five projectiles each held individually within the larger piece of the invention, located again in 4 an 89mm, 12 gauge shotgun cartridge with a roll crimped front. The inner or front piece has the same features as the primary embodiment, the base section 12 is thinner than in the primary embodiment as it is supported by the cup piece 26 from behind. It has four fmgers 13 that hold the projectiles 5, 6, 7, Sand 9, a narrow point 3 where it joins the base 12. It has a gap running through the middle 6 the same as the primary embodiment. The cut away section 33 that forms that narrow point 3, unlike item 2 in figure 1 is not designed to hold the fmgers in an open position, the base section being of much weaker construction. It then has a second piece which as mentioned is in the shape of a cup 26. This piece is designed to contain the inner or front piece of the invention until after leaving the barrel, drag separating the two pieces and the inner or front portion is then free to open and release the projectiles 5, 6, 7, 8 and 9.

Both sections of the embodiment swaging to fit the barrel means one section is not required to pass the spin from engaging the rifling on to the other.

The longer delay in opening for this embodiment means it is less affected by the gases passing it immediately after leaving the barrel, making it better able to cope with being used in different barrel lengths or with slower burning propellants.

In figure 15. The two piece embodiment is shown separated with the inner piece beginning to open. The outer cup section 26 is shown with it's front edge 27 turned out, having been held flat within the cartridge in figure 14. The increased drag of the fingers of the turned out front edge of the cup section 26 aiding separation from the front section once it has left the bane!, assisted by the conical inner surface shape where the two pieces meet and the lubrication between the two sections.

In figure 16. Shows a view of the cup section 26 of the embodiment in figures 14 and 15, from it's front edge 27 down to the base. It shows the front edge to be formed of separate sections like fingers, in a turned out or curled back position. These fingers able to be closed in to fit around the inner section of the invention and fit inside the cartridge, springing back out to there natural position once the invention leaves the barrel.

In figure 17. You see an illustration of the shot pattern from the invention in figure 1.

The amount of lateral throw off from the centre of the shot pattern can be calculated from the mass of the projectile, distance the projectile is offset from the longitudinal axis of the bore, twist rate of the barrel and the velocity of the projectile. This information can bc used to calculate the position of the off set projectiles 6, 7, 8 and 9, within the sabot. Once the offset from the longitudinal centre of the barrel is known the projectiles are then arranged through 360 degrees about the axis that is at 90 degrees to the longitudinal axis, to form the shot pattern as seen in figure 2. Then to position the pattern correctly on the target, load the ammunition in the chamber of the rifle in a position so that after travelling down the ban-el, it reaches the end of it in such a position that when the projectiles are discarded they form the pattern that you desire. A mark on the cartridge case, or a clear case with a mark on the invention would be methods of showing the position of the projectiles therein. That mark could be used to load the invention in the desired position. A physical feature of the cartridge could also be used to align the cartridges in the desired position in the chamber, such as a form of groove or a shape of cartridge designed to fit in a pre set position within the chamber.

In figure 18. Using this invention you can produce shot patterns that cannot be made in a single shot from a prior art shotgun, such as all five projectiles forming a line as illustrated.

In this shot pattern the projectiles can also be arranged to reduce the effects of yaw in the invention in embodiments where the effect of the propellant gasses around the invention require a greater delay before opening. The order of the projectiles held in the invention being 30, 31, 27, 28, 29 would reduce the yaw caused by the projectiles positions. Yaw in the invention could also be decreased by increasing the drag stabilisation of the invention, by lengthening the base or forming driving bands at the rear to increase the drag, however this would reduce the velocity of the projectiles.

In figure 19, 20 and 21. This embodiment of the invention is shown to fit in a large calibre 25mm rifle cartridge 31 in the position a single projectile would occupy, illustrating that the invention can be used in cartridges other than a shotgun cartridges.

It shows the same basic features of four fingers 13, a base 12, with cut away sections 2 at the base of the fingers where they bend at 3. This embodiment not being in a shotgun cartridge the lip on the front 10 is not required, this changes the air flow over the front of the invention 25 which has an effect on the amount of drag that tries to open the fingers when it leaves the barrel. The figure shows a groove 28 with a lip at it's front, this is used to locate the invention in the correct place within the cartridge and ensure it is held securely. It allows the invention to be crimped within the cartridge without deforming the invention.

In figure 21. You see an embodiment of the invention with the additional feature 30 that again protrudes from one finger 13 into a position it is design to fit in within the finger beside it. The purposes of this protrusion is to stop the propellant gasses behind the invention when fired, penetrating through the join between the fingers of the invention and to link togethcr the fingers of the invention to replace the strength lost by having a smaller base 32 in this embodiment. The protrusion 30 runs from the outside of the invention where it contacts the barrel, through to the projectile inside, where it is positioned to meet the centre of the projectile to stop gases going through the gap in the centre of the invention. This feature is present in each finger 13 of the invention. It is shown in only one location but can be in additional points along the embodiment as required.

Depending on the size and offset of the projectiles 5 and 29. In this embodiment, there could be sufficient room within the larger fingers 1 3 of the invention in the space between the projectiles and the inside of the bore of the barrel then some of that space could be utilized by forming a void in each of the petals to act as a gas expansion chamber to reduce the pressure spike that occurs during firing.

That void being covered by a plastic component of a thickness and form designed to break at a pre set pressure allowing the gases to then enter the void.

This would have the benefit of helping expand the sides of the invention making a better gas seal both between the fingers 13 and between the fingers 13 and the rifling of the bore, helping the invention swage to fit the barrel.

The additional features shown in the shotgun cartridge embodiments such as in figures 7, 10 and 16 could all be made to suit an embodiment for use in the same type of cartridge as shown in figure 19.

While the invention has been described above with reference to specific embodiments thereof, it would be subject to many changes and alterations to adapt it to suit the wide range of variahies it will encounter in use including but not limited to, the projectiles used, type and size of cartridge fired from, powder bum rate, type and length of barrel fired from, velocity it is fired at and the spread of shot required, without departing from the original concept disclosed therein. It is intended to embrace all such changes, modifications and variations that follow in the spirit and broad scope of the appended claims.