CA2909630A1

CA2909630A1 - Shotshell with reduced dispersion of projectiles

Info

Publication number: CA2909630A1
Application number: CA2909630A
Authority: CA
Inventors: Stephen W. Meyer
Original assignee: Olin Corp
Current assignee: Olin Corp
Priority date: 2013-03-15
Filing date: 2014-03-17
Publication date: 2014-09-18
Also published as: EP2972062A4; EP2972062A2; WO2014145719A2; WO2014145719A3

Abstract

An improved shotshell of the type having a hull, a head at the proximal end, propellant disposed in the hull, a wad disposed in the hull distal to the propellant, and a load disposed in the hull distal to the wad. The improvement comprises the load including a plurality of individual shot, at least a portion of which are at least partially surrounded by a friable polymeric that breaks up upon the firing of the shell to release to the shot.

Description

SHOTSHELL WITH REDUCED DISPERSION
OF PROJECTILES
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional Patent Application Serial No. 61/790,025, filed March 15, 2013. The entire disclosure of the above-referenced application is incorporated herein.
FIELD

[0002] This disclosure relates to ammunition and in particular, to shotshell cartridges.
BACKGROUND

[0003] This section provides background information related to the present disclosure which is not necessarily prior art.

[0004] Shotshells can propel a single projectile, such as a slug, or more commonly, multiple projectiles, such as birdshot or buckshot. The dispersion of multiple shot pellets at a given distance from the muzzle affords a greater chance of hitting a moving target than the singular path of a slug.
Thus, a moderate dispersion rate is desirable for some applications, such as waterfowl, upland, and rabbit hunting where the intended target is moving. However, in some applications, such as turkey hunting, the intended target is a relatively motionless and small. In these types of applications, it can be desirable to have a tighter pattern, with less shot dispersion.

[0005] The rate of dispersion of multiple projectile loads can be influenced by gun systems and cartridge design. Tighter constrictions or "choke"
in the muzzle section of the barrel can reduce the dispersion rate of shot pellets to some degree. Cartridge design elements, such as shot type, wad type, and buffering can also reduce dispersion rate.

[0006] Lead was the material of choice for early cartridges because of its density, relative low cost, and easy formability. The easy formability however was also a negative. Soft lead pellets are deformed when subjected to the high acceleration forces of cartridge ignition and with direct barrel contact while being accelerated toward the muzzle. Early cartridges did not incorporate any wad systems. Soft lead shot had direct contact with the barrel. This resulted in a considerable dispersion rate. Eventually wads and shot cups provided a liner or barrier between the shot and barrel to reduce pellet deformation associated with bore contact. U.S. Patent No. 3,092,026, incorporated granulated particles intermixed in the shot column to "buffer" the pellets during acceleration to reduce deformation further. These feature elements reduced dispersion rate. Alternate shot materials, such as steel or tungsten, maintain spherical shape to reduce dispersion, but have other shortcomings, such as low density or extremely high cost.
SUMMARY

[0007] Embodiments of this invention provide a buffering system to reduce or eliminate shot pellet deformation during acceleration at ignition, and preferably enhance pattern performance. The granulated/particulate buffers intermixed in the shot column, as described above, often do not effectively occupy all the space between shot pellets, and thus, still allow some pellet deformation. According to a preferred embodiment of this invention, the shot pellets, or a significant portion of the shot pellets, are substantially completely surrounded by a hard, brittle matrix that provides conformal support of the pellets during cartridge ignition. The matrix preferably substantially completely separates from the shot column a short distance after muzzle exit without significant adherence to the pellets.

[0008] U.S.
Patent No. 34,806 discloses filling pellet interstices with some melted substances, such as grease, wax, or low melt metallic alloys for the purpose of creating a fixed shot charge between two wads. Wax or grease is not sufficiently hard or brittle to buffer the shot, particularly at the temperatures encountered in shotshells, and is unlikely to satisfy the requirements noted.
Low melt metallic alloys would be costly and could add significant parasitic weight to the cartridge payload. U.S. Patent No. 3,422,761 discloses embedding shot pellets in a matrix of polyurethane foam. However, the very nature of foam products creates the undesired air gaps in the shot column that is undesirable for a buffering system. Air gaps in foam can collapse upon ignition and result in significant pellet deformation. U.S. Patent Nos. 4,913,054 and 6,367,388 disclose methods of embedding or containing multiple projectiles as a single projectile until impact with a target. U.S. Patent No. 4,733,611 discloses shot pellets embedded in a wax/Styrofoam matrix, but as described above, a wax-based matrix can be unsatisfactory for buffering.

9 [0009] Embodiments of this invention can provide a buffering system for multi-projectile shot cartridges which provides conformal support to individual pellets to reduce or eliminate pellet deformation. Embodiments of this invention can provide a buffering system for multi-projectile shot cartridges which reduces dispersion rate of the shot pellets after exiting the gun barrel. Some embodiments are capable of meeting or exceeding the pattern performance of tungsten-based shot loads at a considerably lower cost.
BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Fig. 1 is a cross-section of a preferred embodiment of a shotshell cartridge constructed, according to the principles of this invention;

[0011] Fig. 2 is a cross-section of an alternate construction of the preferred embodiment of a shotshell cartridge constructed, according to the principles of this invention; and

[0012] Fig. 3 is a cross-section of a second alternate construction of the preferred embodiment of a shotshell cartridge constructed, according to the principles of this invention.
DETAILED DESCRIPTION

[0013] Example embodiments will now be described more fully with reference to the accompanying drawings.

[0014] A preferred embodiment of a shotshell in accordance with the principles of this invention is indicated generally as 20 in Fig. 1. The shotshell 20 is generally of the type having a hull 22, with a head 24 at the proximal end of the hull. A charge of propellant 26 is disposed in the hull 22. A
wad 28 is disposed in the hull 22 distal to the propellant 26. A load 30 is disposed in the hull 22 distal to the wad 28. The load 30 includes a plurality of individual shot or pellets 32, at least a portion of which are at least partially surrounded by a friable polymeric material 34 forming a matrix 36 that breaks up upon the firing of the shell to release to the shot.

[0015] The hull 22 is preferably a conventional hull made of a polymeric material. The head 24 is preferably made of brass, but it could be made of some other material. The propellant 26 can be any conventional propellant. The wad 28 preferably includes a gas sealing cup wad 38, a ballistic cushion section 40, and a cup section 42 to house the shot or pellets 32.

[0016] The shot or pellets 32 can be conventional round shot of any desired size from birdshot sizes to buckshot sizes. The shot or pellets 32 can be other shapes and sizes, as well. The shot or pellets 32 can be made of lead or lead alloy or other suitable material, including copper, tungsten, bismuth, or steel.

[0017] At least the proximal-most shot or pellets 32 are at least partially surrounded by friable polymeric material 34 (Fig. 3). More preferably, about half of the shot or pellets 32 are at least partially surrounded by friable polymeric material 24 (Fig. 2), and most preferably, substantially all of the pellets are at least partially surrounded by friable polymeric material (Fig. 1).

[0018] The friable polymeric material 34 is preferably a polyurethane. An example of a suitable material is Smash! Plastic . The friable polymeric material preferably has a hardness of greater than about 80 (Shore D).

[0019] Preferably, the matrix 36 in the form of a liquid, is dispensed in the cup section, followed by a charge of shot pellets. Alternatively, the shot pellets can be introduced first, followed by the matrix in liquid form, or the shot pellets and matrix in the form of a liquid can be mixed and introduced together.
In a preferred embodiment, the pellets are pre-coated with a release agent, such as a mold release for example, Universal Mold Release agent, available from Smooth-On, Inc., 2000 Saint John Street, Easton PA 18042, to reduce bonding between the matrix and the pellets. The matrix material is preferably a two-part polyurethane resin, such as Smash! Plastic , available from Smooth-On, Inc., 2000 Saint John Street, Easton PA 18042 or similar material with similar properties. Smash! Plastic has a mixed viscosity of about 900 cps, a cured specific gravity of about 1.036 g/cc, and a hardness of about 80 (Shore D).
Smash! Plastic is prepared by mixing equal amounts of two components, Part A, a modified aliphatic diisocyanate, containing Dicyclohexylmethane-4, 4'diisocyanate, and Part B, a resin.

[0020] Accurately dispensing a two-part resin can be accomplished with a unit, such as the Bartec B1000, a gear pump metered dispenser.

[0021] By introducing the pellets after the liquid matrix, the pellets settle into the liquid matrix, providing a shot column with all spaces between pellets substantially and completely filled by the matrix material. The viscosity and gel time of the resin, permit pellets to fall through the resin, yet resist resin flowing past the cushion wad or powder cup into powder column. A folded tube crimp or top wad and roll crimp provide closure of the cartridge. In one preferred embodiment, the closure includes a frangible top wad. A properly fitted top wad and roll crimp prevents leakage of matrix material during cure/set to allow immediate packing of cartridges.

[0022] After an appropriate cure cycle, the liquid matrix becomes a hard, brittle solid. Upon cartridge ignition and load acceleration, the solid matrix breaks into small particles and travels down the barrel, still occupying the space between individual pellets. At muzzle exit, the shot cup petals deploy and the small matrix particles begin to separate from the shot column. During launch, the hard matrix provides conformal support to individual pellets to reduce, and preferably substantially eliminate pellet deformation. During separation near muzzle exit, the particles can provide a temporary windshield effect, further improving pattern performance.

[0023] In another embodiment of the present invention, shot cups, shot, and matrix are pre-assembled and cured ahead of subsequent loading in the cartridge. The pre-assembled and cured shot cups with the shot in a hardened matrix can be loaded into the hull.
Example 1

[0024] Exemplary shotshell cartridges constructed in accordance with a preferred embodiment of the present invention, were tested against two commercially available shotshell cartridges designed to have tight patterns for turkey hunting applications.
A) Winchester product symbol STH1236, 12 gauge 3" 1-3/4oz Copper Plated #6 lead shot, with PE particles for shot buffering.
B) Winchester product symbol STXS1236, 12 gauge 3" 1-3/4oz Tungsten-based #6 shot, with polystyrene particles for shot buffering.
C) Exemplary cartridges in accordance with the preferred embodiment of this invention, 12 gauge 3" 1-3/4oz Copper plated #6 lead shot, with 4 grams of Smash! Plastic polyurethane resin and pellets pre-coated with Universal Mold Release spray.

[0025] All three samples utilize similar wad systems involving a gas sealing powder cup, ballistic cushion member, and a 4 petal shot cup. All samples were fired in a Remington 870 shotgun with a Rhino .660 choke tube.
Percentages shown, are ratio of pellets in the target area to total pellets in the cartridge, and are an average of ten cartridge patterns each. High pattern percentages equate to reduced pellet dispersion. The results are shown in Table 1.
Table 1 Sample Distance 10" Circle 20" Circle 30" Circle A 40 yards 22% 55% 81%
B 40 yards 32% 73% 92%
C 40 yards 48% 84% 95%
A 60 yards 8% 21% 39%
B 60 yards 12% 32% 56%
C 60 yards 21% 53% 78%

[0026] The data in Table 1 shows the exemplary cartridges (C) had twice the performance of standard lead shot turkey load in most trials (A), and exceeded tungsten-based shot loads (B) in all the trials.
Example 2

[0027] Exemplary shotshell cartridges constructed in accordance with a preferred embodiment of the present invention, were tested against alternate matrix materials identified in previous patents. The cartridges are assembled in similar fashion with the exception of the matrix material. Mold release was not used on samples B, C, or D since the respective patents did not disclose use of such coatings on pellets.
A) Subject inventive cartridges, 12 gauge 3" 1-3/4oz Copper plated #6 lead shot, with 4 grams of Smash! Plastic polyurethane resin and pellets pre-coated with Universal Mold Release spray.
B) Same as above except use of paraffin wax as matrix, per U.S.
Patent No. 34,806.
C) Same as above except use of polyurethane foam as matrix, per U.S. Patent No. 3,422,761. Great Stuff polyurethane foam by DOW was selected for this trial.
D) Same as above, except use of Epic resin Cytec RN1000 epoxy resin with a hardener of EA-02 as matrix.

Table 2 Sample Distance 20" Circle 30" Circle A 60 yards 55% 78%
B 60 yards 10% 22%
C 60 yards 9% 21%
D 60 yards Slug* Slug*
*this matrix did not break up or fracture at cartridge ignition, and traveled to target as single projectile.

[0028] As seen in the table above, properties of the inventive cartridge provides differentiation and enhanced pattern performance over prior art.

[0029] The foregoing description of the embodiments has been provided for purposes of illustration and description. It is not intended to be exhaustive or to limit the disclosure. Individual elements or features of a particular embodiment are generally not limited to that particular embodiment, but, where applicable, are interchangeable and can be used in a selected embodiment, even if not specifically shown or described. The same may also be varied in many ways. Such variations are not to be regarded as a departure from the disclosure, and all such modifications are intended to be included within the scope of the disclosure.

Claims

What is claimed:

1. An improved shotshell of the type having a hull, a head at the proximal end, propellant disposed in the hull, a wad disposed in the hull distal to the propellant, and a load disposed in the hull distal to the wad, the improvement comprising the load including a plurality of individual shot, at least a portion of which are at least partially surrounded by a friable polymeric that breaks up upon the firing of the shell to release to the shot.

2. The shotshell according to claim 1, wherein at least the proximal-most pellets are at least partially surrounded by friable polymeric material.

3. The shotshell according to claim 1, wherein about half of the pellets are at least partially surrounded by friable polymeric material.

4. The shotshell according to claim 1, wherein substantially all of the pellets are at least partially surrounded by friable polymeric material.

5. The shotshell according to claim 1, wherein the friable polymeric material is a polyurethane.

6. The shotshell according to claim 5, wherein the polyurethane is Smash!
Plastic®.

7. The shotshell according to claim 1, wherein the friable polymeric material has a hardness greater than about 80 (Shore D).

8. A shotshell cartridge comprising having a hull, a head at the proximal end, propellant disposed in the hull, a wad disposed in the hull distal to the propellant, and a load disposed in the hull distal to the wad, the load comprising a plurality of projectiles embedded in a hard, brittle matrix which provides conformal support to the individual projectiles during cartridge ignition and projectile acceleration, the matrix separating from projectiles near the muzzle exit; reducing the dispersion of the projectiles outside the firearm compared to a similar cartridges without the matrix.

9. The cartridge according to claim 13, wherein the matrix material has a crush strength over the temperature range from about 0°F to about 125°F, and does not vary from the value at 70°F by more than about 20%.

10. A cartridge according to claim 3, wherein the matrix material has a density of between about 0.25 and about 2.5 gm/cc.

11. A cartridge according to claim 4, wherein the matrix material has a hardness ranging from 75 to 85 Shore D.

12. The cartridge according to claim 5, wherein the matrix material has a hardness over the temperature range from about 0°F to about 125°F, and does not vary from the value at 70°F by more than about 20%.

13. The cartridge according to claim 12, wherein the matrix material is a solid polyurethane resin.

14. The cartridge according to claim 18, wherein the matrix material is Smash! Plastic®.

15. The cartridge according to claim 12, wherein the projectiles are pre-coated with a release agent to aid in the clean separation of the projectiles from the matrix near muzzle exit.

16. The cartridge according to claim 19, wherein the projectiles are pre-coated with a silicon-based mold release.

17. The cartridge according to claim 12, wherein the projectile size ranges from 0.080 to 0.36".

18. The cartridge according to claim 12, wherein the projectiles are made of lead, tin, bismuth, copper, steel, zinc, tungsten, nickel, nylon, or polymers, or mixtures of alloys of said materials.

19. The cartridge according to claim 12, further comprising a top wad closure distal to the load.

20. The cartridge according to claim 24, wherein the top wad is frangible.