US2105993A - Shot shell - Google Patents

Description

Jan. 18, 1938. w,-E. WAGNER SHOT SHELL Original Filed June 24, 1929 ,44 and JMWCA /lv Patented Jan. 18, 1938 PATENT ,OFFICE SHOT SHELL wiuiam awww, unworthy, ontario, canada,

assignor to Western Cartridge Company, East.. Alton, Ill., a corporation oi' Delaware Application June 24, 1929,v Serial No. 373,127 Renewed May 3, 1937 f 8 Claims.

This invention relates to cartridges, and more particularly to shot shells adapted for use in shot guns.

In a shot shell the propellant charge is coniined by wadding, over'which is placed the shot charge and the latter is in tu'rn confined by its covering wad and the turned over end or crimp of the paper shell, while a primer is provided in order to ignite the powder. 'I'he wadding does not, however, form such a tight seal as does the bullet in a riile; accordingly, the conditions encountered in a rifle cartridge and in a shot shell are entirely diierent. Where quick burning powder is used, a highA and rapidly rising initial pressure is applied to the shot charge, causing rapid acceleration thereof followed by rapid falling oil in acceleration during the subsequent stage. In order, therefore, to produce -a high muzzle velocity, it has been heretofore deemedV necessary to employ charges of powder sufficient to produce high initial pressures; the latter are, however, necessarily limited by the limiting breech pressure. These conditions have to a large extent been overcome by the employment of coated or impregnated powder securing a progressive burning of the powder charge -by retarding the initial combustion rate. In such a progressive burning powder, the combustion at the surface will start the shot charge on its course at a lower pressure while the maximum pressure is developed an extended distance along the gun barrel; this latter is due to the increased rate of combustion of the powder grains after the coating or impregnation has been consumed.

Coated powders as commonly used in shot shells are dense nitro-cellulose powders of high nitration coated with a deterrent. Not only are such coated powders more difficult to ignite than double base powders, such as nitro-cellulosenitro-glycerin powders, but they are more hygroscopic and under varying climatic conditions may be more subject to changes in burning rate. 'I'he ballistic properties and characteristics of coated powders may, therefore, be affected by storage under varying climatic conditions. 'Ihese conditions cannot be fully met to the desired extent by variation of the primer charge, but the irregularities may, in fact, be increased. On the other hand, uncoated double base fast-burning powders do not have the desired progressive burning action when employed in shot shells as now constructed.

A powder charge starts to burn from the outer surfaces of the individual grains while suiiicient pressure is being built up to overcome the inertia (ci. 1oz-15) -loaded with a propellant charge of readily ignit- 5 able powder and with regular primers such as have been found most suitable to ignite such powders under different storage conditions, the combustion does not start merely from a layer near the base, but the combustion proceeds and l0 the gases are evolved from a small quantity of powder burning from the surface of grains throughout substantially the entire powder charge. This is even true of a shell provided with a base wad having a cavity or well of rel5 duced diameter in front of the primer and even ilared or stepped, unless the cavity or well is constructed as hereafter described. The purpose of such a base wad as heretofore constructed has really been to partly iill the powder space in the zo shell and make the same available for dense powders without the addition of extra wadsibetween the powder and shot charges, in order that the standard length of the shell might be maintained. Even in such shells, however, the 25 primer flame permeates substantially the entire powder charge; accordingly, where fast burning powder is used even in such a shell, the ignition and the pressures produced will not differ substantially from those produced in shells havingy 30 no cavity in the base, and high velocities cannot, therefore, be attained without dangerously high breech pressures.

In a shot shell, therefore, it is the rate of evolution of the gas which controls the initial pres- 35 sure as well as the final velocity of the shot charge. In a shell employing a progressive burning powder of the coated or impregnated type the initial combustion rate is retarded by the coating or impregnation on each grain, so that 4@ the initial pressure can be maintained fairly low while the working pressure ls sustained an extended distance along the gun barrel.

One of the objects of this invention, therefore, is to provide a loaded shot shell in which the initial combustion rate of the propellant charge is retarded sufficiently to develop a low maximum pressure an extended distance along the gun barrel, while the pressure is sustained to produce a high average pressure, and which has improved features and characteristics.

Another object is to develop a process of controlling the ballistics of such a loaded shot shell in a simple and effective manner.

Another object is to provide a shell and process but in which the initial pressure is kept down while the pressure is sustained even after the shot charge moves out of the shell.

lnated with the powder as to produce a progressive burning action when ilred in a shot gun.

Further objects will appear from the detail description, taken in connection with the accompanying-drawing, in which- Figure 1 is a longitudinal section through a shot shell having a stepped recessed base;

`Figures 2, 3 and 4 are views similar to Figure 1, but showing the dimensioning of a base wad well in accordance with this invention;

Figure 5 is a diagram, showing the relation of pressures Valong the gun barrel in the shells. Figures 1, 2, 3 and 4.

A number of embodiments of this invention will now be described; itis, however, to be understood that these are merely given as examples, as this invention is susceptible of various other embodiments. y

Referring to the accompanying drawing, the shot shell generally, except as hereinafter described, may be of the usual form, comprising a tube l, which may be of paper, a metallic base 2, a base wad 3, and a primer in the form of a battery cup 4.

The charge of propellant 5 is shown as confined by wads 6 and 1,. the yvad 6 being generally of Ycardboard'l `while the wads I are of the compressible type, such as felt wads. The shot charge 8 is confined by a wad 8 secured by a crimp i0. The cartridge or shell so far generally described may be of any suitable or usual construction and, as shown, is of 12 gauge.

Referring now to Figures 1 to 4, the base wad 3 is shown as recessed to provide a cavity or well II in front of the primer, and this well may terminate in a flared part i2, which may be stepped, as shown, and provided with a suitable angle of flare.l In accordance with this invention, however, the well II, which contains a part of the propellant charge, is so dimensioned as to substantially retard the initial combustion rate of the propellant charge. This well is, therefore, dimensioned with reference to the characteristics of the propellant in order to control the ballistics of the shell. 'I'he well diameter is, therefore, contracted suiliciently and its depth extended sufflciently, with reference to the normal 'rate of ignition of the propellant, in order to control the pressure generated by the charge. Figures 1 to 4 show wells of progressively decreasing diameters and of progressively increasing depths; this, as

hereafter described, has a marked effect upon the ballistics of these shells. A practical example and a method of determining the dimensions of the well will be hereinafter more fully described; but at this point it will be well to describe the action of the combination, reference being particularly had to Figure 4.

As the primer gases issue from the flash hole ,of the primer, they are restricted in the confined pendent upon the granulationofv` the propellant; for the diametermust be sumcient to permit free admission of the powder grains in loading andI permit escape of the primer gases from the flash hole of the primer. 'Ihe primer gases issuing from the flash hole are, therefore, not only deilected and muffled by the walls of the well, but also by the powder grains therein. The result is, therefore, that the penetration ofthe charge by the primer flame is restricted so that the initial ignition is practically confined to the charge within the wellr and adjacent the base of the shell. The checking of the primer gases further serves to confine their energy content largely within the well, resulting in'improved ignition of the powder contained therein. y i

of the primer gases and the gases evolved by the* combustion of that portion of the powder charge in and adjacent to the well.- The pressure and temperature, therefore, rise gradually as the lli charge progressively ignites and burns, so that i the velocity of the shot charge moving out of the shell is built up gradually. However, pressure and temperature are maintained not4 only as the shot charge moves out of the shell,.but also as it moves 'for an extended distance along the gun barrel. The propellant charge, therefore, does not burnv rapidly to produce a high initial pressure, as in other shells when equal charges of fast burning powders are used, but the pressure is gradually built' up and sustained for an extended distance along the -gun barrel. On the otherhand, by employing a fast burning powder, in which, however, the penetration by the primer flame is restricted to retard the initial combustion, both pressure and temperature are sustained as the shot charge moves out of the shell; for the propellant in front of the well is ignited by, the combined action of the primer gases and the gases evolved by the combustion of that ,portion of the charge in and adjacent to the well; furthermore liability of failure of ignition of the forward part of the charge is obviated by the use of a fast burning powder. Moreover, the primer charge can be increased to secure the desired ignition on account of the-fact that the penetration of the charge by the primer flame is restricted. Since the penetration of the primer gases is restricted by deflection from the grain surfaces inthe well against the walls of this well, additional control of the ballistics may be secured by Aproper selection ofthe granulation of the powder l large grains than by small grains; accordingly as the deected gas currents meet other large grains of powder, they will be further retarded and deflected sideways and back and penetrate less deeply into the main powder charge than is the case with finer grains, which furnish a more direct course through the body of the powder. 'I'here is, of course, a limit to this action; for if the powder is extremely ne, it will, when compressed, act somewhat like a solid mass, thereby preventing penetration lof the ignition gases altogether; this phase can, however, bedisa, lomos'` regarded, for such a .closely packed ne powder results in such poor ignition and low velocities as to be impractical. In accordance with another embodiment of this invention, therefore, the well may contain powder of a larger granuiationthan the main body of the charge; this granulation being selected with reference 'to the normal rate ot ignition of the propellant and the dimensions of the well as determined. It will, thereforabe seen, that by proper dimensioning of the well and by proper selection of propellant grains therein, the penetration of the charge by the primer flame may be restricted to the ldesired extent to substantially retard the initial combustion vas desired.

In theshot sheller'nbodying this invention, the velocity is mainly determined by the quantity of the propellant charge, while the pressure is adjusted by the dimensioning oi' the well and the granulation of the powder therein. Within limits the pressure is reduced -by decreasing the'di-v ameter or increasing the: depth of the well or b'y increasing the grain size 'of the powder in the well; and the pressure can be controlled by variation of, any or all of these factors. vIt will be understood, of course, that anywell will not necessarilyghave la controlling effect, but adaptation is required, particularly with reference to the character of the propellant.

It will be well at this point to describe a practical method of determining the-dimensions of the lwell with reference to the characteristics or the propellant to beused and the shot charge. Taking a fast burning double base propellant, such as Hercules No. 2 (a nitrofce'llulose-nitroglycerin powder containing 30% of nitro-glycerin and whose grain is a flat disc .055 inch tn diam.- eter and .005 inch thick), for use in a l2 gauge shot shell containing, ior instance, il@ oz. of No. 6 shot, the procedure can be as follows: Let us take, say arbitrarily, a shell formed with a well in the base wad and ,dimensioned as shownin Figure 3. A number of such shells' are Inow'v loaded, each with an arbitrary trial charge of the chosen propellant and with the. desired shot charge and suitably Wadded. `These shells arev now red and tested to determine the velocity and also the pressure. if the Velocity is lhigher or lower than desired or necessary, the propellant: charge is .decreased or increased-respectively and another batch of such shells is loaded with the reyised charge. After the propellant charge required to produce the desired velocity has thus been determined, the pressure may be greater than desired; in fact, unless the baserhas been specially adapted and dimensioned for lthe pro pellant, the pressure will be above the desired limit with a fast burning powder. The procedure is, therefore, to increase the depth or decrease the diameter of the well or alter both until further tests show that the pressure has been reduced to the desired value. 0f course, if the pressure is lower than necessary, the well depth can be de creased or its diameter increased, or both.

The pressure can also be reduced by placing in the well a small charge (such as one grain by weight) of a coarse powder, r,such as a nitrocellulose-nitro-glycerin powder in the form 0iv perforated cylinders of .035 inch diameter, .053 inch length and .007 inch perforation.

If it has been found necessary to change the dimensions of the base well any considerable amount, it may be necessary to revise the quantity l powder Vand the depth and diameter of the base well, itis a very simple matter to secure the deaired relations of velocity to pressure.

Ordinarily, the primer is not varied, either as to the charge or the size of the ilash hole. However, i'or varying primer charges and varyingsizes of ilash hole in the primer the procedureis to increase the depth and to decrease the diameter of the well as the primer charge in- 1 creases or the ilash hole decreases, and vice versa for decreasing primer charge and increasing diameter of ilash hole, until the relation of velocity and pressure is as required. If necessary, the main powder charge can be increased orv decreased slightly to control the velocity by the quantity ot the powder, while the pressure is adiusted .by the dimensions of the well.

In order to show graphically the effect of dimensioning the well with reference to the characteristic of the propellant employed and the effect of grain size in the well, actual results will be given, together with the shell dimensions and granulations of the propellant.

In' this test the shells were dimensioned (in inches) as follows:

' vwell wen Depth er Shell mmm depth Flare diameters steps Fig. l... 392 196 543- .675 196. 125

rig. a .25o .25o .a -.4-. 5-. 565 .075 Each ration. The wedding was composed of felt wadding supplemented by hard wads.

Foliog are the results of the test for velocity and pressure:

Powder No. oi Av. max No* sha1! charge shots Av' vel' pressure Grains An examination of the results will show that the velocity increases with the powder charge; in fact, the energy imparted to the shot charge by the propellant varies as the square of the velocity. Accordingly as the powder charge is increased, the velocity square also increases. Now, ordinarily an increase in powder charge is accompanied by increase in maximum pressure. If, therefore, we should increase the powder charge in Figure l shell from 26 to 28 grains, While we can expect an increase in velocity, we can also expect an increase in the maximum pressure. An examination of the above results, however, shows that where the well has been suitably dimensioned with reference to the characteristics of the propellant, then an increase in the powder charge, while accompanied by an increase in velocity, is actually accompanied by a decrease in pressure. Thus, in the shell, Figure 1, 26 grains of propellant, produce u. velocity of 867feet per second, at a pressure of 10,470 pounds per square inch. Where, however, the well has been reduced in diameter, as in Figure 2, then 28 grains of propellant, produce a velocity of 888 feet persecond, at a pressure of 9,520 pounds per square inch. Moreover, iwhen` the well has`been increased in depth, as between Figures 2 and 3, then 32 grains of propellant,

"l produce a. velocity 01.933 feet per second, at a lpressure of only 9,420 pounds per square inch.

Again, we find that reducing the diameterfstill further, as between Figures 3 and 4, an increasedy charge of 34 grains produces an increased velocity of 947 feet per second, but accompanied by a pressure of only 8,780 pounds per square inch.

Test No. 5 shows the eilect of employing a coarser grain'propellant in the well. In this case 37 grains, including one grain (by weight) of coarse propellant, produceda velocity of 970 feet per vsecond at a pressure of 7,600 pounds per square inch.

/, A comparison of the results is, indeed, striking.

powder charge can Abe' actually increased from .30

to 42%, with resulting increases in velocities of from 9 to412%, but with actual decreases in maximum pressures of from 16 to 27%.

The following are the results of tests obtained with a multiple piston. gun, the readings being 40 taken at distances along the gun barrel, noted in the form of curves.

inches. The shells and their powder charges are as in the preceding table. The number of shots red was in each case ten, except for No. 5, in which there were only ilve shots iired.

u Average pressure at Shell In Figure 5 the results have been plotted in These results illustrate the progressive burningactio'n of the powder charge and the retardation of the initial combustion so that the maximum pressure is developed an extended distance along the gun barrel. The inertia ofthe shot charge is, therefore, overcome in such a mannerthat the shot charge is gradu-l ally moved out of the shell and along the barrel,

but the pressure is sustained an extended distance along the gun barrel. While the differences may not at rst sight' be striking, it must be remembered that an increase of pressure of 740 pounds per square inch as between Nos. 1 and 4, and- 1030 as between Nos. 1 and 5, ten inches 0 along the gun barrel, has an. important eiect upon the ve1ocity,.especially when we keep in mind that the maximum pressure is not increased but, in fact, materially decreased. The work done' areas are considerably greater'in shells loaded' in accordance with this invention than where the shell base is not provided. with a well dimensioned toesecure control of the pressure and ballistic properties.

' From a consideration of Figure 5,y it will be seen v that curve No. l, corresponding to shell, Figure l. has a sharp peak while the pressure drops rapidly, thereby showing that the initial combustionis not retarded substantially. The pressure attending the employement of 26 grains of powder in shell ,No.l also indicates that' the charge is about the desired maximum charge of the particular fast burning nitro-cellulose-nitro-glycerin powder employed. As, however, the well diameter is decreased' or/and the depth increased vfrom 1 through 2, 3 and 4, it will be seen that the/ curve rapidly changes its configuration and ilattens out, not only at the peak but also along the gun barrel. 'I'his would seem to indicate that for a given propellant there is 'a rather definite zone, or field of dimensions, where a decrease in the diameter or an increase in the depth of the well becomes effective to retard the initial combustion substantially and to reduce the maximum pressure substantially. The dimensioning of the well is, of course, with reference to the particular propellant employed;- but, as pointed out above, the proper proportions can be readilyarrived at byf rst determining the charge required to produce the desired velocity and by then varying the well diameter or/and depth until the pressure de' provided with a powder receiving well will at- Dtain the objects of this invention if it has the following characteristics: if the well diameter is not less than 0.10 incl'in order to receive powder grains of practical dimensions; if this well diameter is not greater than 0.30 inch and preferably' between 0.20 and 0.25 inch; if the minimum depth of the well is 0.05 inch plus 0.66 times its diameter and is preferably between 0.20 and 0.25 -inch; the maximum depth of the well is, of course, determined by the depth of the base Wad which is limited in all shot shells by the length of the shell and is generally ilxed by the shot charge, the wadding and the required powder charge.l It will, of course, be understood that the term shot shell is a term wellunderstood by those skilled in the art as meaning -a shell having a primer, a powder charge, a shot charge and, of course, wedding between the powder and shot charges.

It will, therefore, be seen that this invention accomplishes its objects. A shot shell is produced having improved characteristics as distinguished from those of the prior art, and this result is secured in a simple and eiective manner. While theinvention is particularly applicable to the lgeneral type of cartridge as shown and described, it will be understood that this invention is applicable in many cases to other forms and types of cartridges. It will, Ifurthermore, be understood that, while certain theories have been advanced, this has only been done to facilitate the explanation; for this invention is not limited to any particular theory. It will, furthermore, be understood that certain features, operations and sub-combinations are of utility and may be employed without reference to other features, operations and sub-combinations. That is contemplated by and is within the scope of the appended claims. It is, furthermore, obvious that various changes may be made in details and operations,`within the scope of'the appended claims, without departing from the spirit of this invention. It is, therefore, to be understood that this invention is not to -be limited to the specific details and operationsshown and/or described.

Having thus described the invention, what is claimed is:

1. A loaded shot shell having a primer and a propellant charge, the base of the shell having a well containing coarser grained propellant than the remainder of the charge.

1 2. A loaded s liot shell having a primer and a propellant charge, the base of the shell having a well containing coarser grained propellant than the remainder of the charge and the well being dimensioned to control the ballistics of the shell.

3. A' shot shell having a base wad provided with a powder-receiving well whose diameter is not less-than 0.10 inch and not greater than 0.3 inch and whose minimum depth is 0.05 inch plus 0.66 times its liameten 4. A shot shell having a base wad provided with a powder-receiving well whose diameter is bea tween 0.2 and 0.3 inch and whose minimum depth is 0.05 inch plus 0.66 times its diameter.

5. A shot shell having a base wad provided with a powder-receiving well whose diameter is between 0.20 and 0.25 inch and whos-e minimum depth is 0.05 inch plus 0.66 times its diameter.

6.1A shot shell having a base wad provided ,with a powder-receiving well whose depth is about .25 inch and whose diameter is .20 to .25 inch.

'7. A loaded shot shell having a base wad, a

primer therein, a well in front of said primer, the diameter of said well being not less than 0.10 inch and not greater than 0.3 inch and the minimum depth of said well being 0.05 inch plus 0.66 times its diameter, and a powder charge in said shell and in said well.

8. A loaded shot shell having a base wad, a primer therein. a Well in front of said primer, the diameter of said Well being not less than 0.10 inch and not greater than 0.3 inch and the minimum depth of said well being 0.05 inch plus 0.66 times its diameter, and a charge of fast burning powder in said shell and in said Well.

E. WAGNER.

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