U.S. patent application number 14/662432 was filed with the patent office on 2015-12-03 for cartridge and bullet with controlled expansion.
This patent application is currently assigned to HORNADY MANUFACTURING COMPANY. The applicant listed for this patent is Hornady Manufacturing Company. Invention is credited to David E. Emary.
Application Number | 20150345920 14/662432 |
Document ID | / |
Family ID | 45924101 |
Filed Date | 2015-12-03 |
United States Patent
Application |
20150345920 |
Kind Code |
A1 |
Emary; David E. |
December 3, 2015 |
CARTRIDGE AND BULLET WITH CONTROLLED EXPANSION
Abstract
A bullet or a cartridge containing a bullet having an elongated
body with a forward end and an opposed rear end. The body has an
intermediate cylindrical portion between the rear and forward ends,
and the front end of the body defines a cavity. A resilient nose
element is received in the cavity. The nose element may be an
elastomer, and may be a cylindrical body. The cavity may be a
cylindrical bore, and the nose element may be closely encompassed
within the bore. The forward end of the nose element may be flat,
and may be flush with the forward end of the body.
Inventors: |
Emary; David E.; (St. Paul,
NE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hornady Manufacturing Company |
Grand Island |
NE |
US |
|
|
Assignee: |
HORNADY MANUFACTURING
COMPANY
Grand Island
NE
|
Family ID: |
45924101 |
Appl. No.: |
14/662432 |
Filed: |
March 19, 2015 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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14228700 |
Mar 28, 2014 |
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14662432 |
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13779617 |
Feb 27, 2013 |
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14228700 |
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13453877 |
Apr 23, 2012 |
8413587 |
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13779617 |
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12156771 |
Jun 3, 2008 |
8161885 |
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13453877 |
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11130976 |
May 16, 2005 |
7380502 |
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12156771 |
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Current U.S.
Class: |
102/507 |
Current CPC
Class: |
F42B 12/20 20130101;
F42B 30/02 20130101; F42B 12/34 20130101 |
International
Class: |
F42B 12/34 20060101
F42B012/34 |
Claims
1. A 9 mm handgun bullet comprising: an elongated body; the body
having a forward end; the body having a rear end opposite the
forward end; the body having a substantially cylindrical portion
between the rear and forward ends, the cylindrical portion
including an outer surface having a cannelure; the body comprising
a jacket encompassing a lead alloy core; the body defining a cavity
open to the forward end; a resilient nose element, at least a
portion of which is received in the cavity, the nose element having
an exposed front end; and wherein the jacket at the forward end of
the body curves radially inward over at least a portion of the lead
alloy core to form a blunt forward rim that defines an opening to
the cavity.
2. The 9 mm handgun bullet of claim 1, wherein the front end of the
nose element is substantially flush with the forward end of the
body.
3. The 9 mm handgun bullet of claim 1, wherein a length of the nose
element is less than a depth of the cavity.
4. The 9 mm handgun bullet of claim 1, wherein the nose element is
an elastomer.
5. The 9 mm handgun bullet of claim 1, wherein the cannelure is
serrated.
6. The 9 mm handgun bullet of claim 1, further comprising a case
defining a case mouth receiving at least a portion of the body,
wherein the case defines an interior volume containing
gunpowder.
7. The 9 mm handgun bullet of claim 1, wherein the cavity has a
constant cross-section.
8. The 9 mm handgun bullet of claim 1, wherein the cannelure
facilitates bullet expansion upon impact.
9. The 9 mm handgun bullet of claim 1, wherein the body comprises
score lines to facilitate bullet expansion upon impact.
10. The 9 mm handgun bullet of claim 1, wherein the blunt forward
rim of the jacket does not extend over any portion of the nose
element.
11. A 9 mm handgun bullet comprising: an elongated body; the body
having a forward end; the body having a rear end opposite the
forward end; the body having a cylindrical portion between the rear
and forward ends; the body comprising a jacket encompassing a lead
alloy core, the body having at least one feature to facilitate
bullet expansion upon impact; the body defining a cavity open to
the forward end; a resilient nose element, at least a portion of
which is received in the cavity, the nose element having an exposed
front end; wherein the jacket at the forward end of the body curves
radially inward over at least a portion of the lead alloy core to
form a blunt forward rim that defines an opening to the cavity
without extending over any portion of the nose element; and wherein
the nose element is an elastomer having a Shore A hardness less
than or equal to 80.
12. The 9 mm handgun bullet of claim 11, wherein the front end of
the nose element is substantially flush with the forward end of the
body.
13. The 9 mm handgun bullet of claim 11, wherein a length of the
nose element is less than a depth of the cavity.
14. The 9 mm handgun bullet of claim 11, wherein the at least one
feature to facilitate bullet expansion upon impact comprises score
lines.
15. The 9 mm handgun bullet of claim 14, wherein the at least one
feature to facilitate bullet expansion upon impact further
comprises a cannelure in the jacket.
16. A 9 mm handgun bullet comprising: an elongated body; the body
having a forward end; the body having a rear end opposite the
forward end; the body having a cylindrical portion between the rear
and forward ends, the cylindrical portion including an outer
surface having a cannelure; the body comprising a jacket
encompassing a lead alloy core; the body defining a cavity open to
the forward end; a resilient nose element received in the cavity,
the nose element having a front end; wherein the jacket at the
forward end of the body curves radially inward over at least a
portion of the lead alloy core to form a blunt forward rim that
defines an opening to the cavity; wherein the front end of the nose
element is exposed and substantially flush with the forward end of
the body; and wherein the nose element is an elastomer having a
Shore A hardness less than or equal to 80.
17. The 9 mm handgun bullet of claim 16, wherein a length of the
nose element is less than a depth of the cavity.
18. The 9 mm handgun bullet of claim 16, wherein the cannelure
facilitates bullet expansion upon impact.
19. The 9 mm handgun bullet of claim 16, wherein the body comprises
score lines to facilitate bullet expansion upon impact.
Description
REFERENCE TO RELATED APPLICATION
[0001] This is a Continuation of U.S. patent application Ser. No.
14/228,700, filed Mar. 28, 2014, entitled, "CARTRIDGE AND BULLET
WITH CONTROLLED EXPANSION," which is a Continuation of U.S. patent
application Ser. No. 13/779,617, filed Feb. 27, 2013, entitled,
"CARTRIDGE AND BULLET WITH CONTROLLED EXPANSION," which is a
Continuation of U.S. patent application Ser. No. 13/453,877, filed
Apr. 23, 2012, now issued as U.S. Pat. No. 8,413,587, entitled
"CARTRIDGE AND BULLET WITH CONTROLLED EXPANSION," which is a
Continuation of U.S. patent application Ser. No. 12/156,771, filed
Jun. 3, 2008, now issued as U.S. Pat. No. 8,161,885, entitled
"CARTRIDGE AND BULLET WITH CONTROLLED EXPANSION," which is a
Continuation-in-Part of U.S. patent application Ser. No.
11/130,976, filed May 16, 2005, now issued as U.S. Pat. No.
7,380,502, entitled "CARTRIDGE WITH BULLET HAVING RESILIENT POINTED
TIP."
FIELD OF THE INVENTION
[0002] This invention relates to firearms ammunition, and more
particularly to cartridges and bullets with expanding
characteristics.
BACKGROUND AND SUMMARY OF THE INVENTION
[0003] Many popular types of rifles such as lever action rifles
employ tubular magazines, in which a single line of cartridges is
stored in a cylindrical tube parallel to and just below the rifle
barrel. The cartridges are arranged nose first, with a compressed
spring and piston forward of the nose of the forward most
cartridge. The spring pressure transmits through the row of
cartridges, and forces the rear most cartridge into the action when
the action is cycled.
[0004] Because the nose of each cartridge in the tube presses
against the rear of the next cartridge, this raises a critical
safety concern. Centerfire cartridges have primers centered on the
base of the cartridge, and it is essential to ensure that the nose
of one bullet does not act like a firing pin that strikes the
primer of the next bullet. Such forces can occur if a rifle is
dropped, such as from an elevated tree stand, or from recoil upon
discharge. Thus, sharply pointed bullets common to other types of
rifles employing box magazines (in which the cartridges are
positioned side-by-side) are not suitable for tube-magazine
rifles.
[0005] Rifles with tubular magazines are limited to rimfire
cartridges (which do not have a central primer and require a sharp
pinching of the rim to discharge) and to centerfire cartridges
having broad flat noses. Blunt, rounded nose bullets have been
employed, but these are regarded as more risky than flat nosed
bullets. Typically, the flat nose of a suitable bullet has a
diameter of approximately 60% or greater than that of the primer.
This ensures any force transmitted to the primer is distributed
over a large enough area to ensure that primer discharge will not
occur. Cartridges with heavier bullets generally have larger
diameter flat noses, to account for the increased force that the
added mass of a stack of cartridges can generate upon dropping a
loaded rifle, and the increased recoil associated with such
cartridges. The noses of such bullets are generally formed of
exposed lead and are not fully jacketed to provide further
safety.
[0006] While effective to ensure safety, flat nosed or other blunt
bullets are aerodynamically inefficient compared to the sharply
pointed bullets used in other rifles. This means that they lose
more velocity as a function of distance traveled than a sharp
pointed bullet, due to increased air resistance. This effect is
greatest over longer distances. Because of this higher rate of
velocity loss blunt bullets carry less energy downrange than do
pointed bullets. In addition, the reduced velocity at distance
leads to greater bullet drop and crosswind drift, requiring more
compensation by and opportunity for error from the shooter.
[0007] A suitable safe, blunt bullet for a tubular rifle magazine
will generally have a ballistic coefficient (BC) of approximately
0.200 depending on the caliber and weight of the bullet. Sharply
pointed bullets, of comparable caliber and weight, have BC values
typically of 0.250 to 0.350. Thus, a lever action rifle chambered
in 30-30 Winchester is considered effective for deer hunting only
out to about 100-150 yards, while cartridges with spire-point
bullets of comparable weight and muzzle velocities are effective
for deer beyond 250 yards.
[0008] For applications other than tube-feed rifles, it is often
important that bullets have an expansion capability. An expanding
bullet is often more effective to disable or stop the intended
target. For hunting, this means a more lethal and humane effect on
game. For self defense, police, and military applications, it means
that an attacker is more readily incapacitated, ending the
attack.
[0009] One common type of expanding bullet is a hollow point
bullet. This has a central cavity or opening at the nose of the
bullet, which facilitates the hollow forward end flaring outward
upon impact to create a broader profile. This is more disruptive of
tissue, providing the increased effectiveness. However,
hollow-point bullets have certain disadvantages. The amount by
which the bullet expands is critical, with under- and
over-expansion limiting effectiveness. If the bullet does not
adequately expand, then it has less disruptive effect leading to
reduced stopping power, and may over penetrate the target,
endangering bystanders or at least limiting effectiveness by
failing to deliver some of the bullet's energy to the target. An
over-expanded round delivers all its energy to the target, but has
limited penetration. This also diminishes the intended
effectiveness against targets.
[0010] Moreover, if a criminal attacker is wearing heavy clothing
such as denim or leather, the material may clog up the hollow
point, preventing or substantially reducing expansion. Other
problems with conventional hollow point bullets is that an off-axis
impact on hard material such as sheet metal or glass can tend to
cause the hollow point leading edge to bend, closing it up and
preventing expansion upon eventual impact with the target.
[0011] Some bullets have hollow points formed in the bullet body
(typically formed of a lead alloy with a copper alloy jacket) and
with the hollow cavity filled with an element of a different
material. Rifle bullets may have a hollow cavity filled with a
pointed tip element to provide an aerodynamic profile, and which
facilitates expansion upon impact at high velocities. Certain
pistol bullets employ a round plastic ball that partially fills a
bullet's cavity, preventing clogging with clothing material, and
facilitating expansion. While providing some benefits, there
remains a need to generate more effective and controlled expansion
of bullets.
[0012] A particular concern is that while high-velocity rifle
bullets readily expand upon impact, lower velocity rounds expand
less reliably. This is a particular concern for compact pistols
with short barrels in smaller calibers often carried for self
defense. In certain calibers, even a hollow-point round not
suffering from clogging with clothing material may not expand
sufficiently. Moreover, a bullet designed for expansion at lower
velocities may excessively expand when fired from a gun with a
longer barrel generating higher muzzle velocity.
[0013] The present invention overcomes the limitations of the prior
art by providing a bullet or a cartridge containing a bullet having
an elongated body with a forward end and an opposed rear end. The
body has an intermediate cylindrical portion between the rear and
forward ends, and the front end of the body defines a cavity. A
resilient nose element is received in the cavity. The nose element
may be an elastomer, and may be a cylindrical body. The cavity may
be a cylindrical bore, and the nose element may be closely
encompassed within the bore. The forward end of the nose element
may be flat, and may be flush with the forward end of the body.
BRIEF DESCRIPTION OF THE DRAWINGS
[0014] FIG. 1 is a sectional side view of a rifle cartridge
according to a preferred embodiment of the invention.
[0015] FIG. 2 is a sectional side view of a bullet according to a
preferred embodiment of the invention.
[0016] FIG. 3 is a sectional side view of a bullet according to a
first alternative embodiment of the invention.
[0017] FIG. 4 is a sectional side view of a bullet according to a
second alternative embodiment of the invention.
[0018] FIG. 5 is a sectional side view of a bullet according to a
third alternative embodiment of the invention.
[0019] FIG. 6 is a graph illustrating the parameters for various
caliber bullets according to the third alternative embodiment of
the invention.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
[0020] FIG. 1 shows a rifle cartridge 10 as loaded in a tubular
magazine 12 typically attached below the barrel of a lever-action
rifle. The cartridge has brass case 14, and a bullet 16. The case
has a circular rear end 20 defining a central pocket 24 into which
is inserted a primer. The case has side walls 26, and can have a
tapered shoulder 30 leading to a reduced diameter neck, or nearly
straight sidewalls that end in a forward case mouth 34. The case
contains a quantity of powder 36, which is contained by the bullet
16 being partially inserted into the mouth, which is crimped to
secure the bullet in place. The rear of a second cartridge 18 is
shown, positioned just forward of the cartridge, illustrating how
in many instances, the tip of one bullet can be positioned against
the primer of the next cartridge.
[0021] The bullet 16 is a generally cylindrical body, symmetrical
in rotation about an axis 36, with a rear end 40 and a forward tip
42. The bullet has an exterior surface shaped as follows: A rear
portion 44 has a tapered frustoconical "boat tail" surface; a
cylindrical intermediate portion 46 continues forward from the rear
portion with a straight cylindrical side wall that has a
circumferential cannelure channel 50. Continuing, a forward ogive
surface portion 52 has a gentle curve toward a meplat portion 54 at
the tip. The meplat is a small diameter spherical portion. The
ogive has a larger radius (as taken in a plane including the
bullet's axis, as illustrated) than the intermediate section's
diameter (taken in section across the axis), and also a much larger
radius than that of the meplat, as will be quantified below.
[0022] The bullet is formed of a copper jacket 56 having a base
portion 60, with side walls 62 extending forward to a rim 64 at a
forward position on the ogive section, spaced apart from the
meplat. The jacket closely surrounds a lead core 66 that defines a
cylindrical cavity 70 in a forward face 72 of the core. The forward
face is rearward of the jacket edge 64 in this particular
embodiment, and the cavity is concentric with the axis 36.
[0023] The bullet tip is formed by a nose element 74 having a first
shank portion 76 and a second tapered portion 80 formed as a
unitary body of the same material. The shank portion is a
cylindrical portion having a diameter equal to the diameter of the
jacket rim, and which is closely received in the cavity of the
core. The second portion has a larger diameter than the shank at
its base adjacent to the shank. The base of the second portion
forms a shoulder 82, and tapers to form the tip. The jacket rim
tightly grips the base of the shank at the shoulder, to secure the
nose into the bullet body.
[0024] The nose element is formed of a resilient material that
elastically returns to its illustrated configuration after
substantial compression. In the preferred embodiment, the resilient
material is an elastomer with a Shore-A hardness of 80, such as
Texin 285, an aromatic polyester-based thermoplastic polyurethane
from Bayer Material Science AG, Leverkusen, Germany. The term
"resilient" is used herein to distinguish from materials (including
most thermoplastics and common ammunition metals such as copper or
lead) that are essentially rigid, even if they will undergo slight
elastic deformation from which they may recover without permanent
distortion.
[0025] The hardness of the elastomer may vary from the preferred
hardness. A lower limit is required to avoid a nose element that is
so soft it does not withstand anticipated forces, and essentially
allows the next cartridge to make a high energy strike against the
jacket rim. In addition, too-soft material is more readily
inadvertently removed from the bullet, which would result in a
less-safe (and poor-performing) cartridge if used. A lower
threshold hardness of Shore-A 60 is considered minimal, and a lower
threshold of 70 is believed more suitable for most applications. If
the material were too hard, it would generate concentrated forces
at the tip that would behave in the unsafe manner of a conventional
hard plastic or metal tip, with inadequate flexure to absorb energy
and to compress into an adequately broad tip. An upper threshold
hardness of Shore-A 95 is considered as a maximum, and an upper
threshold of 85 is believed more suitable for most
applications.
[0026] While a generally rigid plastic that may compress to less
that 90% of its length without permanent deformation may in some
senses be resilient, it is not considered resilient for the
purposes of this disclosure, which contemplates substantial
resiliency in the manner of an elastomer that can be compressed to
less than 50% of its length repeatedly without permanent
deformation. For this disclosure, "resilient" materials include
rubber, silicone and any other synthetic or natural elastomer, as
well as composite elements including more than one material, and/or
with complex forms, including metal or other springs, compressible
gas-filled bladders or bellows, and the like. Such elements may be
used to construct a "resilient" nose element body, even when they
include materials that would not be considered "resilient" if
employed in monolithic form.
[0027] The essential function of the resilient nose is to prevent
the discharge of the primer of the next cartridge 18 in the event
the rifle is dropped on end, or in response to recoil forces. In
the case in which a tubular-magazine rifle is dropped on the
butt-stock, the entire mass of all the cartridges forward of the
rearmost cartridge generates a substantial inertial force on the
second-to-rearmost cartridge as it rests against the tip of the
rearmost cartridge. If this force were concentrated over the small
diameter of a metal-tipped bullet's meplat, or the meplat of a
bullet tipped with a substantially rigid thermoplastic, this would
generate a high force concentration that may be adequate to
discharge a primer. However, in the preferred embodiment, the tip
readily compresses to a broader, blunter tip, so that forces from
recoil or a drop from a threshold height are distributed over a
much broader area, limiting forces to a safe level below that
needed for discharge. Under substantial force, the resilient tip of
the preferred embodiment is believed to compress to an area of
contact comparable to, or a significant percentage of that of the
typical rifle primer.
[0028] Pointed plastic tips are common in rifle bullets. However,
these are selected to be as rigid as possible, and not used in
tube-magazine rifles. The rigidity is preferred to avoid damage to
the tip during handling and loading, which will generally reduce
accuracy by creating a non-uniform aerodynamic shape, and possibly
introducing eccentricities in the bullet mass. Thus, the use of
softer or more flexible materials is counter to the normal
objectives of bullet design.
[0029] The use of a tapered or pointed tip provides a much higher
ballistic coefficient than a conventional flat-tipped bullet
normally required for tubular-magazine rifles. The overall shape
with the resilient tip is that of a conventional high-performance
spitzer, soft point hunting bullet, with a jacket that comes to an
essentially sharp point (with a small meplat.) In alternative
embodiments, the resilient tip and bullet shape may be selected to
provide any desired bullet surface profile, using the tip as needed
to alleviate the safety concerns discussed above.
[0030] In the illustrated embodiment, the example of a 30-30
Winchester cartridge is shown. The casing is a rimmed centerfire
(not rimfire) design, although non-rimmed, rebated, and belted
centerfire casings may also be employed. The bullet is elastomer
tipped, 165 grains, lead core, and copper jacketed, with an overall
length of 1.100'', and an overall diameter of 0.308 inch. The
length of the ogive section is 0.470 inch, and this section has an
ogive radius of 1.50 inch. The exposed portion of the nose has a
length of 0.101, which is 21% of the total ogive length. In
alternative embodiments, a straight conical form would be
considered to have a large radius of infinite amount, for purposes
of comparing with other dimensions of the bullet. The meplat has a
radius of 0.018 inch. The diameter of the meplat at the transition
to the ogive section is about 0.030 inch, and the diameter of the
largest portion of the ogive portion at the shoulder is 0.131 inch.
This is a ratio of meplat diameter to ogive portion diameter of
greater than 4, which provides a very aerodynamically efficient
sharply pointed profile.
[0031] In alternative embodiments, a purely spherical resilient tip
(all meplat) would be less aerodynamically efficient, and would
have a ratio of 1, it would provide ballistic advantages over a
flat tip as well as safety advantages over a conventional round
tip. Preferably, the ratio is at least 1. The ratio of the ogive
radius to the meplat radius is 37. If the tip surface were
spherical, the ratio would be 1. Any ratio greater than 1 provides
some aerodynamic benefits, but a ratio in excess of 3 is preferred.
For a spire-point bullet having a straight conical forward portion
terminated by a small meplat, (with part of the conic portion
provided by the nose element) the straight portion is considered
for the purposes of this disclosure to have an infinite ogive
radius.
[0032] The diameter of the nose element at the base of the ogive
portion (the same as the jacket forward rim diameter) must be large
enough to provide safety, so that there is an adequate volume of
resilient material to absorb the necessary energy based on a
function of expected forces. For larger cartridges with heavier
bullets, greater forces are expected, and thus the nose element
diameter must be greater. The 30-30 cartridge with the 165 grain
bullet has a ratio of nose element diameter to bullet diameter of
0.131/0.308 or 43%. A ratio of approximately 30 to 35% is
considered minimum. For larger/heavier bullets, this ratio is
generally greater.
[0033] In alternative embodiments, the tip may have any
non-spherical shape and still be considered "pointed." Such shapes
include those with parabolic, hyperbolic, conical or ellipsoidal
sections, or any combination of these or other non-spherical
surfaces of revolution. Certain bullets with a laterally flattened
tip may also employ the resilient tip shape of the preferred
embodiment, even though they are not surfaces of revolution.
[0034] In further alternatives, the resilient tip may have a flange
or skirt that extends rearward of the shoulder, so that a forward
jacket portion is closely covered by the skirt.
[0035] FIG. 3 shows a bullet 100 for the 35 Remington caliber. The
bullet is elastomer tipped, 200 grains, lead core and copper
jacketed, with an overall length of 1.030 inch, and an overall
diameter of 0.358 inch. The length of the ogive section 102 is
0.560 inch, and this section has an ogive radius of 1.75 inches.
The exposed portion of the nose has a length of 0.101, which is 18%
of the total ogive length. The meplat 104 has a radius of 0.018
inch. The diameter of the meplat at the transition to the ogive
section is about 0.030 inch, and the diameter of the largest
portion of the ogive portion at the shoulder is 0.131 inch. This is
a ratio of nose element diameter to bullet diameter, as mentioned
above, of 37%. The bullet 100 has a flat base 106 without a boat
tail, and the lead core 110 extends forward to just rearward of the
forward rim 112 of the jacket.
[0036] FIG. 4 shows a bullet 200 for the 45-70 or 450 Marlin
calibers. The bullet is elastomer tipped, 325 grains, lead core and
copper jacketed with an overall length of 1.050 inches, and an
overall diameter of 0.458 inch. The length of the ogive section 202
is 0.400 inch, and this section has an ogive radius of 1.50 inches.
The exposed portion of the nose has a length of 0.173, which is 43%
of the total ogive length. The meplat 204 has a radius of 0.02
inch. The diameter of the meplat at the transition to the ogive
section is about 0.035 inch, and the diameter of the largest
portion of the ogive portion at the shoulder is 0.235 inch. This is
a ratio of nose element diameter to bullet diameter of 51%. The
bullet 200 has a flat base 206 without a boat tail, and the lead
core 210 extends forward nearly to the forward rim 212 of the
jacket.
[0037] The performance advantages provided by the sleek or pointed
shapes generated by the resilient tips are comparable to the
performance of plastic or metal tipped bullets of the same
shape.
Alternative Embodiment Expanding Bullet
[0038] FIG. 5 shows an alternative embodiment bullet 300 that
differs from the embodiments above in that it does not have a
pointed tip. Pointed tip bullets are especially useful for very
high-velocity applications associated with rifles, where muzzle
velocities on the order of 2000-3000 feet per second are most
common. At these velocities, aerodynamics of the bullet are
important in determining effective range, because less streamlined
bullets with low ballistic coefficients will shed velocity faster,
limiting the effective range (reducing the velocity at a given
distance).
[0039] For other applications not involving distant targets, bullet
shape and ballistic coefficient are less critical. Blunt,
round-nosed, and flat-nosed bullets are commonly used for many
applications. Handgun bullets are typically employed at shorter
ranges than are normal rifle bullets. Targets are usually well
within 100 yards, while many rifle bullets are intended for targets
at several hundred yards. Thus, loss of velocity over the flight
distance is not a significant concern, and blunt-tipped bullets are
often employed. Blunt tipped bullets allow the more efficient use
of limited cartridge volume constraining handgun design, by pushing
more bullet mass out to the forward corners of the envelope, and
pushing the bullet of a given weight farther forward to provide
more case volume for propellant powder.
[0040] Handgun bullets are typically propelled at much lower
velocities that typical rifle bullets, with velocities under 1000
feet per second (fps) at the low range, while most common handgun
rounds used by common self defense pistols being below 1500 fps,
and few if any pistol bullets being intended for velocities over
2000 fps. For instance, the standard velocity for bullets fired
from pistols with standard (4'') barrels in the most common
self-defense and police calibers of 0.380 ACP, 9 mm, 38 Special, 40
S&W, and 0.45 ACP ranges from 800 to 1,100 fps. At these much
lower velocities, expanding bullets such as hollow points do not
reliably expand due to the limited energy available upon impact to
cause expansion. To ensure expansion, bullets must be designed with
features that weaken them more than may be desirable, or which may
generate excess unwanted expansion that limits effectiveness on the
target.
[0041] Handgun bullets also generally have substantially lower
sectional densities compared to rifle bullets. Sectional density
(SD) is defined as the bullet weight in pounds divided by the
square of the diameter in inches. Many common handgun bullets have
SD values on the order of 0.100, with few having SD values over
0.200. Typical pointed rifle bullets have SD values on the order of
0.200-0.300 or above.
[0042] While handgun bullets and rifle bullets generally have these
different characteristics, there may be some overlap at the
extremes of each group. Some bullets are used for both handgun and
rifle rounds, and some cartridges are also commonly chambered in
both kinds of firearms. Thus, what may be described as a typical
handgun bullet is not limited only to that application. The
principles of the invention are intended to apply to any bullet or
cartridge where controlled expansion is desired. Blunt-tipped
bullets are the typical application, but this is not necessarily
the only useful application. For instance, the pointed tip bullets
described above were developed to provide long-flying (high
ballistic coefficient) bullets for tube feed rifles where pointed
tip bullets were previously considered unsafe. However, during
testing and evaluation of these bullets, it was discovered that the
elastomeric core provided the unexpected benefit of controlling
expansion of the bullet upon impact, as will be discussed
below.
[0043] The bullet illustrated in FIG. 5 is a 9 mm caliber, with
specific characteristics and dimension as listed below. It has an
overall diameter 302 formed by a cylindrical rear portion having a
length 304. The rear portion extends to the base 306, which is a
flat surface extending the full diameter of the bullet, except for
only a limited minimal radius at the periphery. The rear portion
has a circumferential groove or cannelure 310 for engagement by the
crimped mouth of a casing that receives the bullet to form a
cartridge. The bullet has a tapered forward portion having a length
312, and tapering to reduced flat nose diameter 313 at a forward
rim 314.
[0044] The bullet has a lead alloy core 316 forming the bulk of the
bullet's mass, and a copper alloy jacket 320 encompassing the core
and defining the bullet's exterior dimensions. In alternative
embodiments, the bullet may be made of any conventional material
and construction, and the novel aspects of the disclosed embodiment
may be applied to future bullet materials and constructions that
may be developed. In particular, the bullet may be made of a single
material such as a solid lead alloy or a solid copper alloy.
[0045] The bullet defines a central cavity 322 open to the forward
end of the bullet. The cavity has a straight cylindrical sidewall
324, and a flat circular floor 326. In alternative embodiments, the
sidewall may have other features, such as score lines to facilitate
expansion, or may have a polygonal cross section for a similar
effect. The cavity has a diameter 330, and a depth or length 332 as
measured from the forward most bullet rim 314 to the floor 326. In
the illustrated 9 mm embodiment, the cavity has a depth slightly
more than the overall bullet length, and a diameter of slightly
less than the bullet diameter. Cavity and cavity insert length to
diameter ratio is typically at least 1.5 to facilitate
manufacture.
[0046] The bullet has a nose element or insert 334 that
substantially fills the cavity. The insert is formed of an
elastomeric material as described with respect to earlier
embodiments, but may have different parameters for particular
bullet designs and intended uses. In the preferred embodiment, the
insert is a straight cylindrical body having flat front and rear
end faces perpendicular to the insert axis. The front face 336 is
positioned flush with the front of the bullet body, and may
optionally be molded with an identifying indicia such as a
manufacturer brand, and model identifier, a caliber identifier, or
other indicia. The insert may be formed of any color material, with
the color optionally being associated with a brand identity, or
indicating other characteristics of the bullet or cartridge. To
provide for manufacturing without the orientation of the insert
being critical, both ends of the insert are the same, providing
symmetry as the ends may be exchanged prior to insertion into the
cavity. The length of the insert is designed to be slightly less
than the cavity depth (by 0.020), so that dimensional tolerances
may be accommodated on assembly to ensure a flush insert front
face. The circular cross-section allows insertion of the insert
irrespective of rotational orientation, simplifying
manufacturing.
[0047] FIG. 6 shows a graph illustrating the results of
experimentation providing desired expansion performance for various
calibers The Y axis shows Shore-A hardness of the insert, and the x
axis shows the product of the bullet's diameter, times the square
of its velocity, divided by 100. This illustrates a diagonal band
of desired performance, above which expansion is excessive, and
below which expansion is inadequate. For any new caliber, the
hardness of the insert that will provide optimum expansion is a
Shore A value of 1/250.sup.th of (0.004 times) the X-Axis velocity
function of D.times.V.sup.2/100. Thus, the Shore A
value=D.times.V.sup.2/25000. Where D is in inches, and V is in Feet
per second. There may be variants, as sometimes exponentiation
suggests moderate deviations of Shore A from this nominal value,
such as 1/140 of the X function for the caliber at approximately
5800 and 41.5, and 1/325 for the caliber at approximately 18000 and
55. Preferably, the ratio will be between 1/100 and 1/500 for most
or all typical calibers.
[0048] In alternative embodiments, the insert may have alternate
shapes. The end faces may be concave or convex. The insert's
forward face may protrude from or be recessed in the cavity,
instead of the illustrated flush appearance. Recessing the insert
will make it more vulnerable to clogging with clothing, and causing
it to protrude will generally reduce cartridge performance for a
given overall length. A protruding tip may provide aerodynamic
benefits as discussed in earlier embodiments. If a rounded bullet
nose is desired, the insert may be provided with domed ends.
Preferably, to avoid excessive protrusion, any protrusion is
limited to less than the insert diameter. Where the inserts are
readily oriented before insertion, the ends may have different
characteristics, such as one end flat, and one domes, or the
forward end having an extending flange to cover the nose rim
surfaces of the bullet, to provide enhanced feeding and to prevent
damage. The insert may also have a polygonal cross section such as
a hexagon in alternative embodiments,
[0049] As a general rule for a desired level of expansion, as the
velocity of the bullet increases the size of the cavity and the
insert should decrease and the insert hardness should increase. For
low velocity pistol and revolver cartridges, such as the 380 ACP,
45 ACP and the 38 Special, it has been found that a softer material
of 50-80 Shore A hardness provides very good expansion performance.
For the lowest velocity cartridges with velocities in the 700-800
FPS range, a hardness of no more than 55 Shore A preferred. For
higher velocity ammunition handgun and comparable bullets with
velocities of 1,200 to 1,500 FPS, a hardness of at most 80 Shore A
is preferred.
[0050] As the velocity of the bullet increases, increasing hardness
of the insert is generally provides desired performance. For
typical rifle bullets of 2,500-3,000 feet per second it has been
found that materials of 55-80 Shore D hardness provide optimum
results. Cavity and insert L/D generally runs 1.25-1.75 for desired
results.
[0051] Below is an example of a bullet illustrating the principles
of the invention. [0052] Intended cartridge caliber: 9 mm
(Illustrated to scale in FIG. 5) [0053] Bullet diameter (302):
0.355 [0054] Rear portion length (304): 0.210 [0055] Forward
portion length (312): 0.239 [0056] Diameter (313) of nose: 0.170
[0057] Cavity diameter (330): 0.155 [0058] Cavity length (332):
0.250 [0059] Cavity length/diameter ratio 1.61
[0060] Experimentation employing the principles of the above
invention has shown that by using a relatively soft elastomeric
insert, or protruding tips with an extension shank to fill a cavity
in the bullet, the terminal expansion performance of these bullets
can be dramatically improved and tuned to the specific bullet,
velocities and application. The size of the hollow cavity and
insert, and length to diameter ratio (L/D) and hardness of the
insert can all be adjusted to attain the desired terminal
performance and change the terminal performance for a desired
effect.
[0061] An engineer skilled in the art of bullet manufacturing can
adjust many or all of these parameters to create prototypes of
varying characteristics, and then test these prototypes by firing
into a flesh-simulation medium such as gelatin. If overexpansion is
found, the insert hardness may be increased, or the length/diameter
ratio may be increased. If underexpansion is found, the converse
may be tested. Different bullet alloys and materials may be
similarly tested and compensated for. Bullets for cartridges for
longer barrel (higher velocity) firearms may be tuned with
parameters to limit expansion, than for shorter barrel
applications. Bullets for cartridges loaded for higher velocities
(even of the same nominal caliber) may be designed with suitable
parameters that differ even for bullets of otherwise identical
characteristics of shape and weight.
[0062] The mechanism that is believed to control the expansion
performance is that the insert fills the large cavity in the nose
of the bullet and distributes the forces present when the bullet
encounters an expansion media (such as flesh). The insert fills the
cavity and prevents the impact forces from causing the cavity to
expand all at once. The flexible insert is believed to transmit the
hydro-static forces of initial impact to the entire cavity, but
prevents the entire cavity from experiencing these forces all at
one time. The end result is believed to be that the cavity achieves
the same expanded bullet diameter as a cavity without the insert
but this expansion is spread out over a much greater distance and
time.
[0063] This results in a wound cavity of the same diameter as a
conventional hollow point bullet without the insert, but the large
wound cavity diameter extends to a much greater depth, and the
total penetration of the bullet is much greater. Essentially, by
deferring expansion, greater initial penetration may be achieved,
with the expansion deferred but not diminished. It is believed that
the insert prevents the cavity in the front of the bullet from
opening all at once and acting like a parachute, which would cause
the bullet to rapidly lose its momentum and limit its effectiveness
and penetration.
[0064] The relatively soft elastomeric material employed provides
design flexibility and bullet performance that cannot be achieved
by any other known means. The hollow cavity, insert design, cavity
L/D ratio, and the hardness of the insert can all be adjusted to
optimize the performance of a specific bullet depending on the
bullets velocity, caliber, jacket design and core hardness.
[0065] Terminal performance of existing hollow point pistol bullets
can be significantly improved by placing a larger hollow cavity in
the nose of the bullet, filled with a relatively soft elastomeric
insert. Testing has shown increases in expanded diameter of low
velocity pistol bullets of 10-25% depending on the bullet.
Expansion media temporary cavities have been increased in diameter
by 15-25% and in depth by 25-50% without substantial reduction in
total bullet penetration. The same bullet with the same hollow
cavity without the insert exhibits similar temporary cavity
diameters but lacks the increase in cavity depth and typically
loses 25% in total penetration. Higher speed rifle bullets have
shown 10-25% larger temporary cavity diameter and 25-50% deeper
wound cavities with higher retained weight and penetration than
comparable bullets without a soft polymer tip or
cylinder/shank.
[0066] The relatively soft elastomeric insert also has terminal
performance benefits for pistol and revolver bullets for Law
Enforcement applications. The insert in the hollow cavity prevents
the cavity from being plugged by clothing and thereby preventing
cavity expansion, which would drastically reduce the terminal
performance effectiveness of the bullet. The insert also prevents
the hollow cavity from collapsing when the bullet strikes sheet
metal, such as a car door. When typical hollow point bullets strike
sheet metal, they have the hollow cavity crushed shut, and upon
exiting the sheet metal will not expand when encountering expansion
media. The insert prevents the hollow cavity from closing up when
impacting sheet metal and preserves the terminal performance
characteristics of the bullet.
[0067] Previous pistol bullet designs have employed a hard polymer
sphere in the nose of a bullet, which will not provide the low
velocity performance improvements that the above described design
will. The cavity in prior art bullets is believed to be too small
or of the wrong shape to be effective at low velocities, and the
ball material is too hard to provide adequate transfer of the
available hydrostatic forces. Higher velocity rifle projectiles
with a tip and shank have traditionally had tips made from either
metal or hard plastic. Although these materials provide adequate
results at high velocities, they provide no performance advantages
at lower velocities associated with longer range impacts.
[0068] Testing has also shown that the relatively soft insert
materials provide higher bullet retained weight for both high and
low velocity bullets after impacting expansion media. This increase
is associated with the softer material's ability to distribute
forces more uniformly and help prevent localized high sheer forces
that cause bullets to lose jacket and core material when they
impact expansion media.
[0069] While the above is discussed in terms of preferred and
alternative embodiments, the invention is not intended to be so
limited.
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