US2341264A - Ammunition - Google Patents

Description

Feb. 8, 1944. c.-D. coxE AMMUNITION Filed June 12, 1940 Illlllllllllllllllllllf A .N D D W R E A FH LV m m m l m m w M @d MR w M AY L L4 H M uw u E4 N 1 0. T .MC 9% W UC RU s. G0 ML A E. N M ma m mm w m. R H wv B RN L4 N T lIlrlIRIANISIEI. E lM G A CA A E V T G C T ON N A N 5l IL w|w|f M N. ZRR B Y T0 o @XF L E U n0 L 0 A J# w 5 Patented Feb. 8, 1944 AMMUNI'rioN Charles D. Coxe, Bridgeport, Conn., assigor to Remington Arms Company, Inc., a corporation of Delaware Application June 12, 1940, Serial No. 340,003

' compared to steel. lIn the embodiment disclosed,

the use'of steel is shown as applied to a cartridge case and also for other of the ammunition components such as, for example, shot shell heads and center fire primer cups. In the use of metals for a cartridge case, it has been found that the metal must have a sufficiently high yield strength so that the case will not bulge under theurgence of the powder pressures and appreciably remain in the bulged condition, thereby preventing extraction of the case from the chamber of the gun. It is also necessary that the metal be sufliciently ductile and in such a condition that splits will not occur near the mouth of the case upon firing of the cartridge. Gilding metal has been found to work satisfactorily in the standard loads and to give the desired results. There have been many attempts to use steel but such has never proven feasible. The other objects of the invention will appear from the following description and illustrations which, as stated before, are not intended to limit the invention to the form shown and described. L

In the drawngl. l

Fig. 1 is a sectional view of a rimiire cartridge case after it has been red in the chamber of a *gun wherein the clearance between the case and the chamber of the gun is shown exaggerated. The bulging of the shell due to firing pressures and a split in the case are also shown' in exaggerated form.

Fig. 2 shows diagrammatically, by wayof example, sectional views of flve stages in the forming of a rimflre shell from a flatblank to the finished rimlre case.

Fig. 3 is a graph showing the percentage of splits and extraction force required for various cartridge cases treated in various manners.

'I'he conventional gun is provided with a chamber into which the cartridge case fits, the clear,-

Vprevent staisfactory extraction.

ance between the cartridge case and the chamber being governed by many factors. The cartridge case is properly sized in the course of manufacture to fit into the chamber, but the fit will vary due to manufacturing tolerances of the cases as well as the tolerances in the machining of 'the `chamber of the gun. Also the roughness or smoothness of the chamber of the gun will affect the operation and extraction of the case from the chamber. As the cartridge is fired, the pressure of the powder gas forces the projectile through the barrel of the gun, and, at the same time, the cartridge case is forced radially outwardly to ll the clearance substantially completely, thereby sealing the powder gases and preventing the escape thereof backward through the working mechanism of the gun instead of acting to force the projectile through the barrel. It is evident from this that the metal of the case must have suilicient resilience to return into its original condition so that the case may be extracted fromv the gun after firing the shell. The yield strength must not have been passed appreciably in this preceding action, for otherwise the case will stay, at least partially, in its bulged condition and The yield point may be defined as the point before which no plastic deforation takes place. The metal o'f the case must also be in such a condition that there will be suiiicient ductility so that the case will not split upon firing. Referring to Fig. 1, there is shown a`conventional rimflre shell in which I0 represents the bolt of the gun which has been closed on the head II- of the case I2, the case I2 fitting within the chamber I3 of the barrel I4 of the gun. Extractor I5 of a conventional type engages the rim of the shell so that as the bolt is withdrawn or operated, the shell will be removed from the chamber. The usual striker or firing pin 22 is provided to strike the rim of the case I2 wherein the priming mixture is located. In the illustration, the section is across the receiver, and it is to be noted `that the point of 'contact of the striker and the shell is at or near the edge of the rim of the shell. If the yield point has been exceeded, the case will remain bulged outwardly, for example, as seen in exaggerated form at I6 of Fig. 1, and splits will occur, as at I1, if there is insuflicient ductility or the grain structure of the metal is such as not to allow the stretching of the metal as the propellant charge is ignited. In the manufacture cf cartridges and ammunition, particularly of the smaller calibers, it is the usual practice to employ .charges and powders giving dif- I and not split upon firing.

ferent velocities. These mayfbe classied generally as the high velocity and .low or standard velocity. In order to obtain the high velocity, it is necessary that a larger powder charge be used or a charge be employed which will develop higher pressure or characteristics to force the projectile outwardly through the barrel at the desired velocity. In the conventional .22 caliber long rimre shells, the high velocity bullets leavei the gun at about a velocity of 1375 feet per second, and powder pressure developed within the barrel is in the neighborhood of 18,000 pounds per square inch. This is in contrast to the standard of lower velocity cartridges, wherein the velocity may be in the neighborhood of 1030 feet per second, with a powder pressure developed in the barrel of 14,000 pounds per square inch. By the invention herein described, it has been found possible to use steel, relief annealed, in place of brass or gilding metal for both high and standard velocities. It is necessary in the selection of the metal to beused that due regard be given to using a metal that will properly draw in the manufacture of the cartridge case or component.

In Fig. 2, A, 1B, C, D, E, are shown some of the steps in the drawing of a conventional rimre shell, although, as previously stated, the invention is not limited to the type and form shown, and the number and form of operations may vary., In A is seen a cross section of a flat blank, and B is the same blank after it has been cupped, the usual practice being for the blankl A to be cut from a strip and cupped by the same punch. C, D and E show the succession of forms as the cup B is drawn through the various dies and finally headed at E. When the case is in the .form shown in E, it is not satisfactory for use as a cartridge case, and must be properly heat treated to give the desired results.

The grain structure of the steel as it is cold worked during the drawing of the shell is placed in a strained condition which must be relieved by heat treatment in order for the shell to satisfactorily function in the gun, extract with ease, It is possible that there is a partial recrystallization during this heat treatment. It is to be understood that the time of treatment dependson the material or precise alloy used and the temperature of the relief anneal and is not limited to that shown.

. In Fig. 3 are shown the results of tests on cartridge cases of different metals treated in different manners. The force in pounds required to extractv the cartridge from the chamber of the gun after it has been red andthe percentage of splits occurring are shown. A gilding metal case requires about 13 pounds extraction force when it is fired with a standard load, and a gilding metal case fired with a high-velocity load requires in the vicinity of 32 pounds. The standard load gilding metal case. is considered satisfactory.

A carbon steel case as drawn requires about 27 pounds extraction force after ring, and about 5% of those fired will have body splits. It is.

If an alloy ste'el be used of the analysis simii lar to that set forth below, there will be 57% of the cases split and 41/2 pounds extraction force is relief 'annealed at 498 C. for one hour will give no split shells, andthe extraction force required will'be about 14 pounds, which is satis- .factory for the 'high velocity loads. It is seen,

therefore,'that the relief annealed alloy steel gives results that are better than carbon steel as drawn or relief annealed, and is comparable to the gilding metal standard load fired characteristics.

Considerable strain is set up in the rim portion of the shell as it is formed, which tends to affect the sensitivity or the energy required to be directed against the rim vof the shell in order to insure that the priming mixture will be ignited.

The sensitivity is increased by the relief anneal- Per cent Carbon .10 Manganese .50 Nickel 1.50 Chromium .75

Steels containing not over .50% carbon and, preferably,4 .10% carbon, containing any of tlfe following elements, singly or in combination: chromium, cobalt, copper, manganese, molybdenum, nickel, phosphorus, silicon, titanium, vanadium in such quantities as to cause a substantial increase in the yield point will be satisfactory. As an example of this, the increase of from 35,000 pounds per square inch for carbon steel to 50,000 pounds per square inch for alloy steel before shaping without making the steel unworkable in the forming and pressing operations, will give satis'factory results.

As other examples, there may be cited a steel.

containing:

Per cent Carbon .15 Nieke] 1.50

or, a steel of the following composition:

Per cent Carbon .09 Chromium .48

Manganese 1.47 Silicon .54

It is to be understood, however, that these are merely specific examples and are not to be construed as limiting the invention thereto. Other alloying elements may also be employed within the steel.

.The stress relieving heat treatment removes the internal stresses in the component.

In order to obtain the necessary characteristics for proper extraction and strength, particularly for high velocity loads, it has also been found possible by heat treatment of the components to obtain the correct strength in the finished component, as well as to secure this by means of alloying metals. Before the final draw, such as after the operation at Fig. 2-C, the component may be heated so that it is in the austenitic eld, and then cooled at such a rate that the nal structure is neither austenite nor pearlite, but is in a hardened transition phase between austenite and pearlite, being in the group which consists of martensite troosite, sorbite and bainite, and also includes these in their tempered form.

The succeeding drawing operation, such as to obtain the form shown in Fig. 2-D, will workharden the metal, and the strength will be correspondingly greater than if the component had not been hardened byheat treatment before the drawing, due to the fact that the initial strength before work-hardening was increased by the heat treatment. strength, due to the work hardening, is greater than the increase of tensile strength by work hardening steel that has not been thus heated before the final draw, because it has been found that the ilne dispersion of the carbides increases strength obtained by work-hardening over that obtained by work hardening of steel that does not have the carbides thus dispersed. The dispersion of the carbides may also be obtained by heating to the austenitic field and cooling in air, which is known as normalizing. The rate of increase of strength in cold shaping increases with the dispersion of the carbides. At this point. the component has more than'suiilcient strength, but it is so hard that it will not perform properly and would split in the chamber of the gun upon firing. It is necessary, therefore, to stress relieve the component, and such may be done by subjecting it to a temperature and for a time sufficient for this purpose, as has previously been pointed out. There will be a resultant loss in strength, but because the strength was suiciently high after the unal draw, the residual strength after the stress relieving treatmentwill be suf-- ilclent so that the shell will perform satisfactorily. In the stress relieving treatment, the component has been given the proper ductility to prevent splitting and also to give it the proper sensitivity. It is to be understood that it is merely necessary that the ilne dispersion of the carbides be made before a iinal or last cold shaping takes place, and that if the drawing be done in one operation, that the single draw would be the same as the final draw.

As a specific example. a steel containing .22% carbon was treated by ilrst cupping the blank, as at 2B, following which it was annealed at a temperature in the vicinity of 620 C. so as to.

facilitate the succeeding drawing operation. It was then drawn to la form approximately as shown in Fig. 2-C. Following this, it was heated to about 980 C., which is in the austenitic field, and then quenched in oil. It was then tempered for one-half hour at about 590 C. At this point, the component has the carbides finely dispersed. The component was then drawn, placing it in the form similar to that of 2-D, and then cut on to the proper length and headed so as to be similar to that of Fig. 2-E. Following this, it was stress relieved at a temperature of about 450 C. for one hour, and the shell required lessthan about five pounds extraction force and no splits occurred. As another example of treatment following the 4drawing operation of Fig. 2-C, the component may be normalized by heating to about 930 C. and allowed to cool so as to nely disperse the carbldes, it not being quenched in oil, nor tempered, as in the previous example. Following the normalizing treatment, it was treated and shaped similar to that of the rst The amount of the increase of example. The extraction force in thiscase was In order to perform satisfactorily in the high velocity loads, it is desirable that the residual yield point strength of the completed component inch. The elongation should be at least Athe equivalent of 5% in 2, preferably about 10% or more, this being diilicult to determine because the usual length of a shell, such as a .22 caliber, is shorter than 2". The Brinell hardness of the completed component should be at least 230, and preferably about 240.

It is to be understood, however, that these figures` are examples of characteristicsfound to give satisfactory extraction and performance characteristics, and that they may vary.

It is apparent from the foregoing description that a new method and a new ammunition component have been produced that will be more economlcal to produce, and that will be satisfactory in their performance. The steel shells will not be subject to season cracking. and certain powders and priming materials may be used therein without difculty. As this is believed to be the first time a satisfactory steelammunition component and method of producing the same have been provided, it is not to be limited to the details and composition as shown herein, but is to be broadly construed as covering all equivalent devices and processes falling within the scope of the appended claims.

What is claimed is:

l. In the manufacture of cartridge cases from.

to work hardening in the cold shaping will be suillcient so that the decrease in strength due to the stress relieving anneal will leave the required strength in the finished case.

2. In the manufacture of cartridge cases from low carbon steel having a carbon content between about .09% and about .5% by drawing and annealing, the method comprising the steps of heating the case to the austenitic field, treating the case so as to obtain a hardened transition phase between pearlite and austenite, cold shaping the case, and tnen heating to a temperature between aboutA 300 and 550 C, for a period between about four hours and ten minutes, the hardening treatment and last mentioned heating being so coordinated that the increase in strength due to work hardening in the cold shaping will be Sullicient so that the decrease in strength due to the stress relieving anneal will leave the required strength in the nished case.

3. In the manufacture of cartridge cases from low carbon steel having a carbon content between about .09% and about .5% by drawing and annealing, the method comprising the steps of normaliznig said case to increase the rate of work hardenablllty and obtain a strength so coordinated withthe relief anneal that the increase of strength due to worl; hardening in the nal cold shaping will be sufficient so that the decrease of strength due to the stress relieving anneal will leave the required strength in the finished case, cold shaping the case, and then subjecting the coldtshaped cas to a stress relieving heat treatmen CHARLES D. COXE,

A I CERTIFICATE CF CORRECTION. Patentuo. 2,52I1l,26l. February 8, 191m.

CHARLES D. com.

It is hereby certified that error appears in the printed speclficatien of the above numbered patent requiring Correction as follows: Page 1, sec-g ond cQlumh, line 28 for "deforat'ion" read "deformation-j; page 2, first column, line 11.1?, for "of" read .or; and that the said Letters-Patent should be read with this correction therein that the seme mayv conform to the record of the cause in the Patent Office. Y

signed and sealed this 18th day ofApru, A. D. 19ML.

Leslie Frazer (Seel) Acting Commissioner of Patents.

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