U.S. patent application number 10/492985 was filed with the patent office on 2005-01-06 for 5.56 small arms ammunition.
Invention is credited to Booth, Derek.
Application Number | 20050000385 10/492985 |
Document ID | / |
Family ID | 29286765 |
Filed Date | 2005-01-06 |
United States Patent
Application |
20050000385 |
Kind Code |
A1 |
Booth, Derek |
January 6, 2005 |
5.56 Small arms ammunition
Abstract
Described herein is a round of ammunition for firing from a gun
having a rifled barrel, especially a small arms weapon. The round
comprises a body core (7) which has a plurality of knurl lines (9)
and associated grooves (6) formed over a portion of the body core
(7). Jacket material (11) is provided over the body core (7) such
that the inner diameter (10) of the jacket material (11) makes
contact with the knurl lines (9). During firing of the round, the
jacket material (11) deforms into the grooves (6) formed between
the knurl lines (9) enabling the rifle engraving to take place with
a substantially reduced axial force.
Inventors: |
Booth, Derek; (Nr Crewe,
GB) |
Correspondence
Address: |
NIXON & VANDERHYE, PC
1100 N GLEBE ROAD
8TH FLOOR
ARLINGTON
VA
22201-4714
US
|
Family ID: |
29286765 |
Appl. No.: |
10/492985 |
Filed: |
April 16, 2004 |
PCT Filed: |
March 16, 2004 |
PCT NO: |
PCT/GB04/01108 |
Current U.S.
Class: |
102/514 |
Current CPC
Class: |
F42B 12/74 20130101;
F42B 12/78 20130101 |
Class at
Publication: |
102/514 |
International
Class: |
F42B 010/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 27, 2003 |
GB |
0307274.1 |
Claims
1. The combination of a gun having a rifled barrel and a round of
ammunition; the rifling of the barrel comprising rifling grooves
which are separated by lands extending helically along the length
of the barrel; the round of ammunition comprising a projectile; the
projectile having a body comprising at substantially cylindrical
body comprising a plurality of splines or knurl lines producing a
corresponding plurality of grooves which extend along the length of
a section of the main diameter of the main body; a deformable
jacket means substantially surrounding a proportion of the diameter
of the main body corresponding to the section of said main body
comprising said splines or knurl lines; wherein the body of the
projectile is formed from a metal having a Vickers Hardness of not
less than 550 HV, and the maximum diameter of said main body
comprising said splines or knurl lines being substantially equal to
or less than the minimum internal diameter of the weapon
barrel.
2. A combination according to claim 1 wherein the projectile has an
ogival nose portion of the body forward of said forward body
portion.
3. A combination according to claim 1 wherein the depth of said
grooves is between about 1% and 10% of the nominal diameter of the
projectile.
4. A combination according to claim 3 wherein the depth of said
grooves is between about 2% and 6% of the nominal diameter of the
projectile.
5. A combination according to claim 1 wherein the projectile body
is made of a material selected from the group comprising steel,
tungsten, alloys of tungsten, and tungsten carbide.
6. A combination of gun and ammunition according to claim 1 wherein
the diameter of the main body is less than or equal to the diameter
defined by the roots of the said rifling grooves.
7. A combination of gun and ammunition according to claim 6 wherein
the diameter of the main body is substantially the same as the
diameter defined by the roots of the said rifling grooves.
8. A combination of gun and ammunition according to claim 1 wherein
the diameter of the body portion is less than or equal to the
diameter defined by the said lands.
9. A projectile for use in a combination as claimed in claim 1; the
projectile having a main body comprising a substantially
cylindrical body portion, and a plurality of longitudinally
extending knurl lines or splines resulting in corresponding grooves
along said main body; wherein the body of the projectile is formed
from a metal having a Vickers Hardness of not less than 550, and
the maximum diameter of said main body comprising said splines or
knurl lines being substantially equal to or less than the minimum
internal diameter of the weapon barrel.
10. A projectile according to claim 9 wherein the depth of the said
annular groove is between about 1% and 10% of the nominal diameter
of the projectile.
11. A projectile according to claim 1 wherein the projectile body
is made of a material selected from the group comprising steel,
tungsten, alloys of tungsten, and tungsten carbide.
12. A projectile according to claim 1 having nominal calibre of 9
mm or less.
13. A projectile according to claim 12 wherein the said nominal
calibre is 5.56 mm.
14 and 15. (Canceled)
Description
[0001] This invention relates to ammunition for use in a weapon
having a rifled barrel, and especially to an improved form of
projectile for small arms ammunition.
[0002] When a projectile is fired from a rifled barrel, the
projectile must deform as it travels along the barrel so that
material forming part of the projectile is forced into the spaces
between the lands forming the rifling. This process is called
engraving, and causes a spin to be imparted to the projectile by
virtue of the longitudinal twist of the rifling.
[0003] The deformation of the projectile, its travel along the
barrel effectively as a force fit to the rifling, the high linear
acceleration imparted by the gun propellant on firing, and the
consequent high rate of angular acceleration and associated force
acting between rifling and projectile all contribute to substantial
wear on the barrel.
[0004] If this wear rate can be reduced, substantial benefits
follow, including increased barrel life, higher muzzle velocity and
hence increased accuracy and lethality.
[0005] For this reason, low friction, readily deformable materials
are normally selected for small arms bullets, for example lead. In
order to increase the overall density of the bullet, it has also
been proposed to use steel. However, steel is not readily
deformable, and causes unacceptable barrel wear. On the other hand,
hardness is a very desirable characteristic for the bullet
material, in order to minimise nose tip ablation during penetration
of hardened targets such as, for example, titanium/kevlar body
armour. For these purposes, a Vickers Hardness of at least 550
(using a 10 kg load) is the minimum desirable.
[0006] In seeking to overcome these problems, it has been common
practice to make a small arms bullet from a steel core, enclosed in
a gilding metal jacket.
[0007] This latter solution is practical, but results in a bullet
having a relatively expensive construction. This is a very
significant disadvantage since small arms ammunition is consumed in
large quantities, and the market for such ammunition is highly
competitive.
[0008] In U.S. Pat. No. 5,686,693 there is disclosed a 7.62 mm
bullet formed from a steel alloy, having a forward body portion
whose diameter corresponds to that of the rifling lands of an
associated gun, and a rearward body portion having a greater
diameter, and provided with annular grooves. The body is provided
with a coating which can be of copper. In use, the copper coating
acts as a lubricant, and is less thick than the depth of the
rifling. When fired from the rifled barrel, the rifling therefore
cuts through the copper coating so that the steel body of the
bullet is engraved by the rifling. In the disclosure it is stressed
that the steel of the body must be soft, so as to permit this
engraving to occur without undue barrel wear. The maximum value for
the hardness of the steel body mentioned in the disclosure is 210
Brinell, which equates to a Vickers Hardness of 213, i.e. very much
less than the desirable minimum value of 550 Vickers Hardness. As a
result, the bullet disclosed in U.S. Pat. No. 5,686,693 will lack
the desirable target penetration capability.
[0009] It would therefore be a considerable advantage if a way
could be found to utilise steel or other metal having a Vickers
Hardness equal to at least 550 (using a 10 kg load) as the
principal component of a small arms projectile, while enabling the
projectile to be engraved by the rifling and not introducing
unacceptable friction or wear, and avoiding the expensive
construction of applying a jacket to the projectile.
[0010] According to the present invention there is provided the
combination of a gun having a rifled barrel and a round of
ammunition; the rifling of the barrel comprising rifling grooves
which are separated by lands extending helically along the length
of the barrel; the round of ammunition comprising a projectile; the
projectile having a body comprising at substantially cylindrical
body comprising a plurality of extending splines or knurl lines
producing a corresponding plurality of grooves along a section of
the main diameter of the body; a deformable jacket means
substantially surrounding a proportion of the diameter of the main
body corresponding to the section of the main body comprising said
splines or knurl lines; wherein the main body of the projectile is
formed from a metal having a Vickers Hardness of not less than 550
HV, and the maximum diameter of said main body comprising said
splines or knurl lines being substantially equal to or less than
the minimum internal diameter of the weapon barrel.
[0011] Normally, the projectile will also have an ogival nose
portion of the body forward of said forward body portion, although
other forms are possible.
[0012] The main body of the projectile should normally have a
diameter which is not greater than that defined by the roots of the
grooves of the rifling. Upon engagement with the rifling the knurl
lines or splines are designed to deform into the groove air gaps
corresponding to said splines or knurl lines, and thus engaging
with the lands, inducing spin in the projectile due to the twist of
the rifling. This deformation gives the body an interference fit
with the rifling so as also to provide effective obturation by
restricting or preventing the escape of propellant gases past the
projectile via the rifling grooves. The length and precise diameter
of the body should be designed with these factors in mind.
[0013] Regard must also be taken to ensure that the force required
to effect the deformation of the jacket material and to propel the
projectile along the barrel is not excessive, and this is the
reason why the diameter of the body should not normally be greater
than that of the rifling groove. This force is substantially
reduced by the presence of the air gaps between the knurl lines or
splines allowing the material to deform into said groove air gaps
during the passage of the body along the barrel.
[0014] The depth of said grooves of knurl lines should preferably
be between about 1% and 10% of the nominal diameter of the
projectile, and an optimum design may be between 2% and 6%.
[0015] The material selected for the projectile body will depend
partly upon the function which the projectile is to perform, but in
the case of High Performance Ammunition should not usually be below
a Vickers Hardness of 550 HV.
[0016] For a warshot ammunition nature to be used in combat
conditions, steel is a suitable material, as it is inexpensive and
can be readily formed into the desired shape, eg. by a cold-forming
process. Tungsten is another possible material because hardness is
an important characteristic for target defeat, as are alloys of
tungsten, and tungsten carbide.
[0017] The invention is particularly but not exclusively applicable
to small arms weapons systems, having a nominal calibre of 20 mm or
less, especially 9 mm or less.
[0018] The invention will now be described by way of example only
with reference to the accompanying drawings, of which:
[0019] FIG. 1 shows a diagrammatic representation of a round of
small arms ammunition incorporating grooves of knurl lines
projectile for use in combination with a gun having a rifled
barrel, in accordance with the invention; and
[0020] FIGS. 2A and 2B each shows a cross sectional elevation A-A
through the projectile shown in FIG. 1, additionally depicting the
envelope of said projectile.
[0021] As shown in FIG. 1, a small arms ammunition projectile 1,
comprising a main body portion 2, a tip portion 3 and along the
main body a plurality of grooves or knurl lines 4 producing
corresponding splines 5 and air gaps 6.
[0022] The projectile body is of elongate form and is cold formed
from steel having a Vickers Hardness of at least 550. It can
subsequently be given a heat treatment to provide the desired
hardness or other physical properties. The projectile comprises a
body 2 of substantially cylindrical form.
[0023] Because of the substantial hardness of the projectile body
material, the projectile is highly effective at penetration of
targets such as titanium/kevlar body armour. Moreover, the hardness
also serves to minimise ablation of the projectile tip profile,
thus further contributing to its effectiveness in target
penetration.
[0024] FIGS. 2A and 2B show representative cross sections A-A on
FIG. 1. In FIG. 2A, the detail of the knurl lines 9 and associated
`groove` air gaps 6 of the projectile body core 7 is shown when the
projectile body core 7 is located within surrounding jacket
material 11. Similarly, in FIG. 2B, the splines 5 and associated
`groove` air gaps 8 of the projectile body core 7 is shown when the
projectile body core 7 is located within surrounding jacket
material 11.
[0025] When the body 9 and associated coating 13 passes from the
gun chamber into the rifled part of the barrel, by virtue of its
greater diameter, the jacket material 11 deforms into the
corresponding groove air gaps 6, 8 corresponding to the splines 5
or knurl lines 9. The internal diameter 10 of the jacket material
11 should preferably be substantially equal to or less than the
diameter of any rifling grooves (not shown).
[0026] The presence of the grooves 6, 8 facilitates the necessary
deformation of the jacket material 11, thus enabling the rifle
engraving to take place with a substantially reduced axial force.
The fact that the jacket material 11 can deform into the grooves 6,
8 contributes considerably to a dramatic reduction in the axial
force required for engraving to occur.
[0027] Therefore, despite the hardness of the material forming the
main part of the projectile body, barrel wear from this factor is
minimised.
[0028] It will be evident to the skilled addressee that all of
these factors reducing the engraving force will also result in
reduced barrel wear, higher muzzle velocity, and hence increased
lethality and accuracy.
[0029] The projectile which forms part of the combination of gun
and ammunition tile according to the invention is also considerably
less expensive to manufacture than a corresponding conventional
projectile in, for example, a gilding metal jacket.
[0030] The optimum design parameters for the projectile according
to the invention can be determined by those skilled in the art,
based on the teaching contained herein.
[0031] The invention is particularly but not exclusively applicable
to small arms ammunition. In one particular example, the invention
has been successfully applied to 5.56 mm gun and ammunition.
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