U.S. patent application number 11/131045 was filed with the patent office on 2006-12-14 for shotgun shell with slug.
This patent application is currently assigned to Hornady Manufacturing Company. Invention is credited to Jeremy Millard.
Application Number | 20060278114 11/131045 |
Document ID | / |
Family ID | 37522945 |
Filed Date | 2006-12-14 |
United States Patent
Application |
20060278114 |
Kind Code |
A1 |
Millard; Jeremy |
December 14, 2006 |
Shotgun shell with slug
Abstract
A firearm shell has a hull with a hull chamber and a rear end
containing a primer. A hull side wall extends forward from the rear
end to a front end. A powder charge is contained within the hull at
the rear end. A sabot is positioned forward of the powder charge,
and has a base and forwardly extending side portions defining a
cup. A projectile has a forward end and a rear end received in the
cup. A cushion is provided in the hull, rearward of the bullet. The
cushion may be an elastomer such as silicone, and may be positioned
immediately behind the bullet, forward of the base of the
sabot.
Inventors: |
Millard; Jeremy; (Grand
Island, NE) |
Correspondence
Address: |
Langlotz Patent Works, Inc.;Bennet K. Langlotz
Patent Attorney
P.O. Box 759
Genoa
NV
89411
US
|
Assignee: |
Hornady Manufacturing
Company
|
Family ID: |
37522945 |
Appl. No.: |
11/131045 |
Filed: |
May 16, 2005 |
Current U.S.
Class: |
102/439 |
Current CPC
Class: |
F42B 7/02 20130101; F42B
14/064 20130101 |
Class at
Publication: |
102/439 |
International
Class: |
F42B 30/00 20060101
F42B030/00 |
Claims
1. A firearm ammunition component comprising: a hull defining a
hull chamber; the hull having a rear end containing a primer, and a
hull side wall extending forward from the rear end to a front end;
a powder charge within the hull at the rear end; a sabot forward of
the powder charge; the sabot having a base and forwardly extending
side portions defining a cup; a projectile having a forward end and
a rear end received in the cup; a compressible cushion element
received between the base of the sabot and the rear of the
projectile.
2. The firearm ammunition component of claim 1 wherein the cushion
is a flat disc.
3. The firearm ammunition component of claim 1 wherein the cushion
is an elastomer.
4. The firearm ammunition component of claim 1 wherein the cushion
is formed of silicone.
5. The firearm ammunition component of claim 1 wherein the cushion
has a hardness of greater than 40 on the Shore-A scale.
6. The firearm ammunition component of claim 1 wherein the cushion
has a hardness of less than 65 on the Shore-A scale.
7. The firearm ammunition component of claim 1 wherein the cushion
has a hardness in the range of 40 to 65 on the Shore-A scale.
8. The firearm ammunition component of claim 1 wherein the sabot
includes a driver element in the base, wherein the driver element
is formed of a first material and the sabot is formed of a second
material, and wherein the first material is more rigid than the
second material.
9. The firearm ammunition component of claim 8 wherein the driver
is a planar element having a width greater than the diameter of the
projectile.
10. The firearm ammunition component of claim 8 wherein the driver
is a disc having peripheral radiused edges.
11. A firearm ammunition component comprising: a hull defining a
hull chamber; the hull having a rear end, and a hull side wall
extending forward from the rear end to a front end; a powder charge
within the hull at the rear end; a sabot forward of the powder
charge; the sabot having a base and forwardly extending side
portions defining a cup; a projectile received in the cup; and an
elastomeric cushion element in the hull, rearward of the
projectile.
12. The firearm ammunition component of claim 11 wherein the
cushion is formed of silicone.
13. The firearm ammunition component of claim 11 wherein the
cushion has a hardness of greater than 40 on the Shore-A scale.
14. The firearm ammunition component of claim 11 wherein the
cushion has a hardness of less than 65 on the Shore-A scale.
15. The firearm ammunition component of claim 11 wherein the
cushion has a hardness in the range of 40 to 65 on the Shore-A
scale.
16. The firearm ammunition component of claim 11 wherein the
cushion and projectile have diameters sized to be closely received
in the cup.
17. The firearm ammunition component of claim 11 wherein the
cushion is peripherally constrained by a portion of the sabot.
18. A firearm ammunition component comprising: a projectile; a
sabot having a base and a plurality of petals extending forward
from the base to define a cup; a compressible cushion received in
the cup adjacent to the base; and the projectile being received
within the cup with the rear end of the projectile against the
cushion.
19. The firearm ammunition component of claim 18 wherein the
cushion includes an elastomeric material.
20. The firearm ammunition component of claim 18 wherein the
cushion has a hardness in the range of 40 to 65 on the Shore-A
scale.
Description
FIELD OF THE INVENTION
[0001] This invention relates to firearms ammunition, and more
particularly to shotgun cartridges containing a single
projectile.
BACKGROUND AND SUMMARY OF THE INVENTION
[0002] While shotguns are normally used for firing shot shells
containing multiple projectiles, certain shotgun shells fire only a
single large projectile. Such projectiles are known as "slugs" (as
are sometimes the shells themselves.) The shell consists of a
hollow hull with a base containing a primer, and an open forward
end that is crimped to enclose the contents, and to open upon
firing. The rear of the hull is filled with gunpowder. A
disc-shaped gas seal element is positioned forward of the powder to
provide a barrier in the hull. An elongated cup-like plastic sabot
is positioned forward of the gas seal, and contains the bullet or
slug. The sabot is open at the forward end, with elongated slits
extending to the forward end to define "petals," so that the petals
open and the sabot falls away from the slug after it exits the
muzzle of the shotgun. The shotgun has a rifled barrel to generate
rotation of the sabot and slug, so that the slug is stabilized in
flight.
[0003] To provide additional projectile velocity or energy without
increasing chamber pressures above reasonable limits, prior art
slug shells have employed "cushions" between the gas seal and the
sabot. Such cushions have been made of a compressible material such
as felt or cardboard. Cushions for slug shells and absorb some of
the initial spike of pressure that occurs immediately upon firing,
and return this absorbed energy well before the projectile exits
the muzzle. Thus, the energy is preserved, but the initial pressure
spike is reduced, allowing more energetic powder loads than would
otherwise be possible while complying with a maximum pressure
threshold. Essentially, the cushion allows the lighter gas seal to
move forward as the cushion is compressed, providing slightly
greater volume even as the heavier slug's inertia resists movement
and expansion.
[0004] While effective in some applications and for certain
combinations of bullet weight, type, and powder load, the existing
cushions are limited in effectiveness for certain other slug
designs, yielding poor accuracy. Moreover, the location of the
cushion between the gas seal and the sabot prevents the integration
of these components. In addition, the exposure of the cushion edge
to the barrel limits material cushion choices (to avoid barrel
fouling), and limits materials to those that do not flow outward
against the barrel wall when compressed.
[0005] The present invention overcomes the limitations of the prior
art by providing a firearm shell. The shell has a hull with a hull
chamber and a rear end containing a primer. A hull side wall
extends forward from the rear end to a front end. A powder charge
is contained within the hull at the rear end. A sabot is positioned
forward of the powder charge, and has a base and forwardly
extending side portions defining a cup. A projectile has a forward
end and a rear end received in the cup. A cushion is provided in
the hull, rearward of the bullet. The cushion may be an elastomer
such as silicone, and may be positioned immediately behind the
bullet, forward of the base of the sabot.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a sectional side view of a shotgun slug shell
according to a preferred embodiment of the invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
[0007] FIG. 1 shows a shotgun slug shell 10 having a hull 12
containing a charge of powder 14, with a gas seal element 16
forward of the powder, a sabot 20 forward of the seal, and a slug
22 contained in the sabot. A cushion 24 is positioned in the sabot
to the rear of the slug, and the sabot includes a driver element 25
to the rear of the cushion.
[0008] The hull 12 is a conventional hull, with a brass rear
portion 26 having a flat rear face 30 defining a primer pocket 32
receiving a primer 34. A cylindrical skirt sidewall 36 of the brass
portion extends forward from the rear face 30. A plastic
cylindrical tube 36 extends forward from the brass portion to
define a cylindrical chamber in which the other components are
received. The tube has a inward crimp 40 at the forward end to
secure the components, and the crimp is opened upon discharge of
the shell. In the illustrated embodiment, the hull and other
components are shown sized for a 12-gauge shell, but any other
gauges may be employed.
[0009] The gas seal element 16 is a disc of low density
polyethylene or other suitable plastic, with a concave rear face
42. The gas seal skirt expands to fill the hull chamber, so that it
operates like a gas piston when the powder burns, containing the
combustion gases, and pushing the sabot and slug forward. The gas
seal has a diameter of 0.730 inch, an overall thickness of 0.275
inch, and a thickness at the middle of 0.188 inch.
[0010] The sabot 20 has generally cylindrical form, with a flat
circular base 44 from which a generally tubular side wall 46
extends in a forward direction. The side wall is slit into four
sections or petals by elongated slits 50 parallel to the sabot
axis. The slits extend to the forward rim 52 from an intermediate
position 54 along the length of the sabot toward the base. The
sabot is formed of a flexible high-temperature low-friction
thermoplastic material such as low density polyethylene or other
suitable material and has a diameter of 0.735 at the base, which
has a thickness of 0.180 inch. Forward of the base, the sabot
defines a cylindrical lozenge-shaped pocket 56 with a diameter of
0.600 inch and a depth or thickness of 0.150 inch. Forward of the
pocket 56, the petals define a cylindrical interior diameter of
0.500. Thus, the sidewall thickness of the sabot is thinnest (0.068
inch) at the pocket 56 (contrast the petal thickness of 0.117).
This facilitates the "blooming" of the sabot petals on its exit
from the muzzle, as the thin sections provide a hinge or bending
point at which the petals tend to easily flex. The slits that
define the petals extend back to the thin pocket section, so that
their termination 54 is aligned with the forward limit of the
pocket 56.
[0011] The pocket 56 in the rear of the cup formed by the sabot is
fully filled by the driver disc. The driver disc is a flat, rigid
disc of polycarbonate that serves to transmit and distribute the
force of powder discharge from the gas seal to the bullet. It has a
diameter of 0.600 inch, and a thickness of 0.150 inch, with the
circular edges at each face radiused with a radius of 0.015 inch.
The radiused edges prevent sharp edges from cutting into the sabot
material in discharge, which can in extreme instances sever the
base of the sabot from the petals. The disc has a small axial hole
for the purpose of mold orientation. The use of a relatively rigid
driver disc provides the benefits of even force transmission, while
allowing the use of a flexible, low-friction sabot material to
facilitate petal blooming, and low-friction engagement of the
rifled barrel bore employed for shooting the shell of the
illustrated embodiment.
[0012] The cushion is a disc of silicone rubber or other suitable
elastomer or polymer. The cushion has a thickness of 0.125, and a
diameter of 0.500, with a radiused edge having a radius of 0.015.
The cushion has flat, parallel sides, with one side resting
directly on the driver disc. The smooth driver disc face and flat
face of the cushion provide good adhesion to each other under the
pressure of firing and to facilitate the impartation of torque to
the bullet as the sabot angularly accelerates due to being advanced
down the rifled barrel bore. The cushion is formed of silicone
rubber with a durometer hardness in the range of 40-60 on the
Shore-A scale. In the preferred embodiment, a hardness of 50 is
used, with the range of 40 to 60 being considered the ideal range.
In this range, the cushion is hard enough to withstand the forces
of firing without excess deformation (which could allow the slug to
cant off axis, impairing accuracy). Also, the selected cushion
material is compliant enough to grip the slug, and to provide the
desired energy absorption that allows more energetic powder loads
as discussed in the background above. Outside of the 40-65 range,
the cushion lacks these functional advantages. In alternative
embodiments, the optimum hardness may vary depending on the gauge,
and the slug configuration.
[0013] The slug is a copper-clad lead-cored bullet with a hollow
point filled with a plastic nose to provide an aerodynamic tip with
a curve that follows the curved ogive 60 of the forward end of the
slug. In the preferred embodiment, for 12-gauge shells, it has a
weight of 300 grains, although this may vary widely depending on
the need. A slug for a 20 gauge shotgun may weigh 250 grains, for
instance. The slug has an essentially flat base 62, with sharply
radiused corners 64 at the periphery of the base. The rear portion
of the slug from the base to the ogive is a straight cylinder with
a diameter of 0.500 inch, the same as that of the petal bore and
the cushion. The slug is secured during storage, transport, and
during the recoil of firing prior shells by a rib 66 on the
interior surface of each sabot petal, just forward of the
cylindrical slug portion, to closely receive the ogive. Thus, the
rear of the slug is retained closely against the cushion for
firing.
[0014] The close fit of the slug and cushion in the petal bore
ensures that the cushion is not merely distorted during firing, but
is compressed in volume. If the cushion were placed between the
rear of the sabot and the front of the gas seal, it would extrude
outward unpredictably, possibly in an eccentric manner. If the
cushion were sized to the diameter of the sabot and gas seal, it
would press outward, generating friction, and likely fouling the
barrel as the outwardly-extruded elastomer rubbed against the
barrel. In the preferred embodiment, the cushion is entirely
isolated from the interior of the hull and the barrel bore by the
sabot petals.
[0015] Upon firing, the primer is struck, causing the powder to
burn, generating propellant gases. The initial expansion of these
gases pushes the gas seal forward (flaring the rear rim outward to
maintain a seal and to avoid gas leakage). This directly pushes the
sabot forward. Initially, the forward motion of the sabot
compresses the cushion as the heavy slug's inertia resists
movement. This allows the initial gas pressure spike to be
significantly reduced to desired levels improving the efficiency of
the propellant. The sabot accelerates under the gas pressure,
sliding forward in conjunction with the gas seal until it has burst
through the crimped portion of the hull at the forward end. Upon
departure from the hull and entry into the barrel, the sabot's
cylindrical outer surface (as well as that of the gas seal) engages
the rifling of the barrel. This generates an impulse of rotation,
which accelerates as the sabot and slug gain velocity while
proceeding through the barrel. Under the force of the expanding
gases, the slug receives pressure through the cushion that adheres
the slug base to the cushion (and the cushion to the driver disc
and thereby sabot). This pressure and adhesion allows the cushion
to efficiently transmit the torque to the slug, so that the initial
impulse of torque does not disrupt the position of the slug, but is
transmitted over a more extended period, reducing stresses and the
prospect of disruption of slug orientation.. Alternative materials
such as plastic, fiberboard, and felt do not provide this adhesion.
However, in alternative embodiments, such materials and any other
compressible material may be suitable for use as a cushion
immediately to the rear of the bullet. Similarly, elastomeric
materials may be employed as cushions between a gas seal and
sabot.
[0016] While the above is discussed in terms of preferred and
alternative embodiments, the invention is not intended to be so
limited. For instance, the gas seal may be molded as an integral
part of the sabot, which is not possible with a cushion positioned
in the conventional position therebetween.
* * * * *