Note: Descriptions are shown in the official language in which they were submitted.
~ W094/OD730 213 8 5 ~ ~ PCT/SE93/00~63
Soft steel projectile
This invention relates to a bullet or a projectile for firearms,
preferably riflebores, and more specifically to a projectile made
of steel, the employment of steel for producing such a projectile
and a method for producing said projectile.
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-; The present~ interna~ional application is based~on my pending
national swedish application nr 92 01967-8 from which priority
is claimed for corresponding features.
The predominant material used in rifle bore bullets is lead (Pb),
;~ most frequently~ surrounded by a jacket made from copper-zink
alloy or from plated steel. On one handj the jacket functions as
- a~protection for the soft lead core against external deformation,
and on the other hand to allow firing at~ the high muzzle
velo~ities connected with modern firearms. At these velocities,
a non-jacketed bullet would deposit lead in the barrel bore due
to~friction heat. Fur~hermore, in game hunting, the jacket
increases the bulle~s effect upon impact in that it preserves the
form of~the lead core as the bullet penètrates the game and
;thereby permits a desired, deep penetration. This later aspect,
of~course~ is of little importance in the field of practis~- and
contest shoating. ~ ;
The~jacketed Iead bullet is manufactured through several steps.
Jacket blanks are punched from a jacket plate and formed to a i
sleevè~through two or more form pressing operations. The lead
core~, possibly with antimony added to increase the hardness, is
d~aw~formed through tapered bores to have the accurate gaugej and
cold formed to fit the~jacket. In a joining operation the lead
;~ core is fitted within the jacket, whereupon a close fit between
core and jacket is of utmost importance, since the occurance of
airpockets would cause unbalance with the bullet, resulting in
a; poor score. In the joining operation, multiple tools are
employed, gen~rally up to six tools, between which ~he bullets
and jackets are moved under the operation, and finally the
aompleted bullets are controlled with respect ~o e.g. gauge and
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The Jacketed lead bullet is available in multiple embodiments,
among which the common feature is, that the varied shapings
particularly in the sense of jacket construction, are contempla-
~, ted to increase the effec~ and penetration ability of the buIlet
upon game hunting. However, the major part of firearms ammunition
~ is used for practice- and con~est shooting, wherein such
3 ~ prpperties as a fast kill are of no importance. Naturally, for
the purpose of sight adjustment and range finding of hunting
rifles, some target shooting will take place with the ammunition
that later is used for the~ game hunting, bu~ this particular
gallery shoo~ing constitutes merely~à minor part of the total
amount of rifle ammunition fired in practice- and contest
shooting. Considering that one manufacturer of small arms
ammunition alone on the swedish market distributes in the range
of 5 million cartridges for target shooting, and ~nowing that as
~ much as 90-95 ~ of the bullet weight is lead, one readily
T~ realizes that considerable amounts of this ~oxic metal is spread
annually in the environment, and that any measures directed to
1imiting and reducing this deposition of Iead, naturallyj is of
utmost importance.
For smooth barrel guns (shotguns), there are alternatives to the
lead~shot available on the market, even though the lead shot is
st~ predominating. For rifles and handguns, however, no lead
free altsrnative is available to meet the shooters demands of
performance and selling price.
It is therefore an object of the present invention to provide a
small arms projectile with a minimum of lead content, which,
through a simplified manufacturing process will have a low
seIling price compared to the jacketed lead bullet, and with
~ preserved target shooting performance.
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Another disadvantage of the conventional bullet, apparent in con-
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nection with target shooting, is that the bullet upon perforation
of the target produces a ripped holé with grainy edges, often
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~; W094/00730 ~138544 PCT/S93/00563
leading to troublesome interpretation and the use of a drillgauge for determining which target ring that was hit.
Another object of the present invention will therefore be to
provide a small arms projectile, having a shape which contributes
to the punching of a cylindrical through hole with a sharp and
clean edge upon perforation of the target.
These objects are achieved by a small arms projectile with the
features stated in the~appended claims.
The~invention is hereinafter described more in detail, with
reference made to the appended~drawings, of which:
Fig l shows a partially sectioned elevational view of a projec-
tilè according to the invention,
Flg~2~shows a target penetrated by a conventional jacketed~lead
bullet~
Fig~3~shows~;~a target~penetrated by a projectile according to the
inven~ion, and
Fig~4~;sh~ws~a second~embodiment of the inventive projectile.
Fig~ shows~a~projectile or a bullet according to the invention,
generally~indicated by the refPrence numeral l. The bullet l
comprises~a~torpedo~section 2 and a~guide sect1on 3. In its
periphery, the guide section 3 includes circumferentially applied
grooves and protrudin'g lands 4, acting to provide a tight seal
between bullet and rifle bore and thus preventing the powder
combustion gases to pass the bullet. The grooves are provided to
allow~-the material of the lands (4) to ''escape" when being
compressed by the lands of the rifle bore. In the embodiment of
fig. 1, the transition section, between the torpedo section 2 and
guide section 3, comprises a shoulder with a slant-ing front face
5, having an angle to the vertical axis l within a range of 25-
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W094/00730 PCT/SE93/00~63
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3~, preferably 30. The guide section 3 further comprises a
chamfered rear edge 6. In the embodiment of fig 1, the torpedo l~
section 2 is pointed, but the bullet can alternatively ba formed l~
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with hollow or ogive points or with a flat or a round nose. . ~'
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~ Naturally, the projectile of the invention is not limited to the
-~ design shown in fig 1, but can be given any desired shape to meet ~'
thè specific requirements of penetration ability or stopping
effect.
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The~bullet 1 is solid and manufactured from steel of a low carbon
C)~content~(up to an amount of 0.40 ~) and preferably including
lead~(Pb), which adds to the steel an enhanced cutting capacity
(related cutting capacity~ rising from the standard machine-steel i"'
cu~ting capacity index 100 (DIN 9SMn23 or SS 1912) to an inde'x
150~;for the lead-bearlng alloy steel (DIN 9SMnPb28 or BX 1914j.
In~the~present invention~,~ the high machineability of the lead-
bearing~ alloy~ steel ~ls utilized for producing, preferably by 1
turning in a lathe, a small arms bullet which has a competitive
selling'price.
Advantageously, tellurium (Tej can be added to the steel. Tellu-
rium-bearing free-cutting~ steel has a limited i~dustrial
ap~liancP~but~is used~;~e.g. ln tyre'studs and is sold by Boxholm,~
Sweden,~;under the product symbol 1914-04~Te, and~can be obtained
with~a~tellurium additive of 0.02-0.04 ~. This steel alloy
compris~s-lead to an amount of 0.15-0.35'%.
Thus, through the addition of lead and tellurium, the machinabi-
lity of the steel is increased, and in the present invention the
lubricant effect of the tellurium acting in conjunction with the
included lead, is utilized for the~production of a bullet with
a~minimum of lead content, which bullet will not damage the rifle .
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bore upon passage therethrough. It is, by the way, commonly
believed that the high temperature fumes developed under the .
discharge process presents a more serious ~hreat through erosion
of the bor~, especially of the conical section, which is exposed '
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I to the fumes during the free flight of the bullet, that is before
the bullet is completely seated in the bore, than does the
friction wear exerted upon the rifle bore ~y the copper or steel
.~ jacketed bullet.
; In manufacturing, the bullet 1 is advantageously machined in a
lathe and cut off~from a bar,~which c~n be of a somewhat smaller
' diameter than~ the rifle gauge to permit a coating with an
antioxidant compound, such as c~pper, zinc, nickel or a composi-
tion including one or -more of these metals. The coating is
~ advantageously applled electro-chemically,' but can also be
:3 ~ achi~eved through a common jacket blank. The bullet can be
'~ completed within three or four s~eps in an automatic lathe,
provided with a bar magazine feed and a tool adapter for several
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cutters. After machining (and/or after coating) the bullet is
gauged, polished by ~tumbling in fluid, eventually with an
addition of abrasive ~and detergent, whereupon the coating is
applied. An alternative coating is the application of a layer of
polytetrafluoroethylene ~PTFE), which will further decrease the
friction wear during the passage of the bullet through the bore.
Al~ternatively, the~ steel is subjected to~ normalization to
decrease its hardness, e.g. in the case ~w~here the bullet is
manufactured from cold drawn material. However, this is not
cons~idered-to be requested in the purpose of decreasing the
rict~ion wear of the rifle bore, when a tellurium-bearing steel
alloy~;~containing lead is utilized, but can bè advantageous when
other~steel alloys~are-used or to achieve a certain,~ desired
property of the bullet.
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~; In an alternative manufacturing process, the bullet of the
~ invention is formed in a roll forming machine, e.g. of a type
'~ tha~ is manufactured'and sold by Kinefac Corporation, Worcester,
Massachusstts, US. These roll forming machines are high perfor-
- ming'and can produce the inventive bullet at a low unit price.
W094/00730 PCT/SE93/00563 t~
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The soft steel projectile or bullet of the invention has been
subjected to several shooting tests for determination of its
performance under various conditions.
In a first series of shooting tests, the bullet was machined from
steel including a 0.25 percentage of Pb and a 0.04 percentage of
Te.,The bullet was coated with a surrounding Cu-layer of appr.
10 micron. In this embodiment the bullet 1 holds a weight of 62
~ grains (4 g) in caliber 6.5 mm, whereas a jacketed lead bullet
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of corresponding caliber generally holds a weight of 80 to 160
grains (5 to 10 g)j depending on the design and purpose of the
bullet. ~ ~
As expected, the test shooting verifies that the inventive bullet
of relatively small weight gains a comparatively high muzzle
velocity. The test record also shows that the bu}let 1 at this
muzzle velocity obtains good firing groups.
The test~shooting was performed outdoors at noon and with a
humidity of 40 %. Weather conditions showed a slight cloudiness,
light~winds t~ cross wind gusts of 2-8 m/s. The shooting range
was~100-~m and the muzzle~velocities were measured with a Mcd. M1
;chronograph. The test results were compared~to a simultaneously
pe~formed Smith Ves~on laboratory test.
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The~ soft steel bullet was loaded- with a powder charge of 30
grains (appr. 1.95 g~ and achieved with this charge an average
muzzle velocity of 952.4 m/s in a test serles of 10 rounds. The
factory-loaded jacketed laad bullet used as comparison object had
a weight of appr. 93 grains (6 g) and achi~ved an~average muzzle
velocity of 926.3 m/s with a charge of 32 grains (appr. 2.1 g),
likewise in a test saries of 10 rounds.
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~ W094/00730 ~ PCT/SE93/0~63
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MUZZLE VELOCITY M/S
Soft steel bullet, Jacketed lead bullet,
charged manually factory-charged
1. 953 1. 932
2. 945 2. 955 i~
3- 95l 3. 911
4. 954 4. 922
5. 953 5. 923
6. g59 6. 930
7. 960 ~ 7. 925
8. 942 8. 933
9~. 955 9. 9l2
10. 952 ~ ~ lO. 920
For comparison of firing groups the resp. type of bullet was
fired in five series of three rounds each. The firing groups of
the steel~bullet then ranged from 17 to 22 mm,~and the groups Qf
the jacketed lead bullet ranged from 17 to 25 mm.
FIRING GROUPS ~ ~
Soft steel bullet ~ ~ Jacketed lea~d~bullet
22 mm 1. 25 mm
2. 17 mm 2. 20 mm
3.~ 20 mm 3. 22 mm
4. 21 mm 4. 17 ~m
5~ 21 mm~ ~ 5. 18 mm
The~ spread is partly explained by the lrrègular crosswinds
appearing on the~test shooting occasion but the accuracy results
from~the comparison test still verifies the competitive target
shooting~performance of the inventive bullet. ~
Through the slanted shoulder 5 in the transitionary section
between the torpedo section 2 and guide section 3 the effect of
the bullet,upon penetrating ~he target, punching a cylindrical
through hole with clean cut edges will be achieved, see fig. 3.
As comparison, a target being shot through using conventional,
Jacketed lead bullets is shown (fig. 2). In the embodiment, used
in the precision test referred to above, the shoulder of the
bullet 1 is given a slanting angle a to the vertical axis of 30, t
W094/00730 PCT/SE93/00~63 ~
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which, in respect of the air resistance and the punching
efficiency, is considered to be an advantageous chamfer.
The chamfered rear edge 6 of the guide section 3, which prefe-
rably is rounded or has an angle of chamfer of 45~, is considered
to have an advantageous influence on the flight of the bullet by
promoting an even bypass of combustion gases when the bullet
exits the bore at the rifle muzzle.
In a second series of shooting tests, a soft steel bullet o~ the
abovesaid tellurium~bearing ~steel alloy and of the embodiment
shown~in fig. 4 was uséd in the .308 W gauge. In this embodiment,
the~bullet~ comprises lands 4' with rounded off edges and~an
;extended,~ conical guide section 3' with a rounded rear edge 6'.
This second test was accomplished to determine the bullets
performance in conjunction with automatic rifles and machine
guns, and the test was~performed under varying temperature
conditions ranging from -54 to + 52 degrees C. The test shows
tha~t~ the in~entive bullet, with respect to automatic fire
fùnct~ions, is not inferior to a reference~bullet of conventional
type~.~No deposit material was observed in the barrel bores after
shooting.
AUTO FIRE FUNCTION~TEST
Ammunition components
Cartridge: Ordina~y 7.62 cartridge with primer
5~ Powder:~ NC 1055 p 8603Q
Charge: ~ ~ 45 grains~appr. 2.92 g). Pressure appr. 340 MPa
Projectile: According to the embodiment of fig. 4, giving an
overall cartridge length of 70.7 mm. Weight = 124
grains (8.05 g)
Automatic carbine AK4
Rounds Temp ~ Firing rate, rounds/min
+21 730 (Reference ammunition)
2x20 +21 731 (Inventive bullet)
-54 704
+52 731
Machine gun ksp 58
+21 670 (Reference ammuni~ion~
2x20 +21 671 (Inventive bullet)
-54 690 -"-
+52 649
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W094/OU730 213854~ PCT/SE93/0~63
Being produced from a steel alloy in accordance with the
abovesaid, the inventive bullet will achieve enhanced charac-
teristics during the discharge process. At the firing moment, a
rifle bullet is not only exposed to high temperature, but also
to a gas pressure as high as 3.000 kp/cm2 or more, which might
oause damage to a conventional lead bullet, especially during the 2
free flight. With a bullet according to the inven~ion, this
drawback, as well as the drawback of slippage within the rifle 7 '
bore, will be cleared away.
The bullet~l according to the invention is not to be considered
as being limited to the`embodiments, shown in figs. 1 and 4. For
the man, skilled in the art, it is readily apparent that
modifications of the shape of the bullet, such as an extended
guide section or torpedo section to incrPase the weight of the
bullet~or to manipulate the center of gravity, can be accomplis-
hed~to impart other ballistic properties to the bullet. Further-
more, ln game hunting, the torpedo section can be modified to
slow the bullet down upon impact within living targets, e.g. by
shaping the bullet with a hollow or ogive point or a~ flat nose.
The coatlng, in the disclosed embodiments made of copper, could
also~,~;as mentioned above, be composed of zink, nickel, a compound
containing e.g. lead and one or more of these metals and/or -
polytetrafluoroethylene (PTFE). In this respect, the polytet~
ra~fluoroethylene coating can be applied in ~he form of a fully
surrounding protective~layer or in the form~of peripheral rings
around the guide section 3, closely fitting within the rifle
bore.
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~ The initially stated purpose is well accomplished by a bullet
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according to the invention: to provide a bullet, primarely for
practice-and contest shooting, which significantly reduces the
deposition of lead in the environment. Thé addition~of lead of
the bullet 1 amounts to only somewhat more than 1/400 in
comparison with a corresponding conventional bullet. By producing
the bullet, making use of tellurium-bearing alloy steel, a
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lubricant effect that will spare the hore and its lands, is
achieved.
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Shaping the bullet in accordance with the embodiment of fig. 1
also maets with the second object: providing a bullet primarely
for target shooting, which bullet due to its design produces
un~isputable hit markings.
At~thls~stage, it has not been~possi~ie to examine the adaptive-
nèss~of the bullet l for hunting. However, owing to its hardness
and~comparatlvely low weight~the performance of the bullet upon
hitting wild game can be theoretically predicted, even though the
bulle~,~prlmarely,~ is~intended for target shooting.
In the development process, at all times guided by the basic
obj~eat;~to~find a rep}acement for the lead bullet, severaI
'altèrnatives~to,~the~ tellurium bearing steel alloy have been
onsi~dered~and~brought to test. Thus, it is believed that also
obhér composition~metals~can be utilized to prod ce a projectile
or~small~arms, such as~steels containing allc,ying ingredients
whiGh~are~use~d in quallties commonly referred to as free;-cutting
ateels,~e~.g~ silicon (Si), sulphur (S), phosphorus (P) and
manganese~ Mn)~, in some~cases with the addition of e.g. bismuth
t'~ Bi),~ selenium (Se)~or tungsten (W), preferably in combination
with~lead~ These~addi~tives can be utilized to impart specific
characteristics to the bulIet, such-as an increased amount of
phosphorus making~the bullet brlttle and inclined to scatter upon
impact,~;leaving minor~or~no ricochets, or an addi~ion'of tungsten
in~order to increasè~the penetration ability. However, a bullet
made from tellurlum-alloyed steel displays, in conjunction with
; the included lead, an advantageous lubricant effect upon passing
the~bore and upon machining, maklng~ this composition metal
}~ extremely suitable for the purpose.
3 ~ In the~disclosure, the bullet of the invention has been presented
as~a projectlle primarily intended for rifle bores. ~owever, this
' wi~ll not exclude the utilization of the~tellurium bearing alloy
W094~00730 ~ 4 C2
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steel for a projectile intended for smooth ~arrel guns and for
producing round shots. i:
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