US3568600A - Method and apparatus for checking firing pressure of ammunition - Google Patents

Abstract

A method and an apparatus are described for enabling a sportsman to determine the correct amount of powder that he should add to firearm cartridges to produce maximum safe working pressures. A shallow cavity is formed in the sidewall of the cartridge. A calibrated thin metal disc is seated in the cavity with the outer surface of the disc flush with the cartridge wall. The disc has a recessed center section with reduced thickness that is calibrated to deform or bulge outward to make contact with the firing chamber wall when the maximum safe working pressure is exerted on the interior of the cartridge.

Description

I United States Patent 1 3,568,600 7 Inventor John A31 3,345,876 10/1967 Smith 73/167X B d O 3,443,430 5/1969 York etal 73/167 [21] App]. No. 751,286 OTHER REFERENCES 1 Flled Aug-8,1968 Internal Ballistic, published 1951, copy in NY [45] patmed 1971 Philosophical Library; pp. 112. [731 Asslgnee Robe" Amos SMOKELESS SHOTGUN POWDERS; 1935; by Wallace Gales Ferry Conn H. Cox; pub. E. I. duPont NeMours 81: Co., Inc. pp. 73 & 74

' Primary Examiner-Robert F. Stahl [54] METHOD AND APPARATUS FOR CHECKING Attorney-Wells & St. John FIRING PRESSURE 0F AMMUNITION 9 Claims, 6 Drawing Figs.

- ABSTRACT: A method and an apparatus are described for U-S. bli g a sportsman t d t i th correct amount f 73/167 86/23 powder that he should add to firearm cartridges to produce [51 1 llltmaximum safe working pressures A shallow cavity is fomed [50] Field of 73/167, in the sidewall f the cartridge A calibrated thin meta] disc is (lnqmred); 10238143151; 86/1, 20,23 31 seated in the cavity with the outer surface of the disc flush with the cartrid e wall. The disc has a recessed center section [56] References Cited with reduced th ickness that is calibrated to deform or bulge UNITED STATES PATENTS outward to make contact with the firing chamber wall when 1,062,604 5/1913 Pedersen 102/43 the maximum safe working pressure is exerted on the interior 1,123,362 1/1915 Pedersen... 102/43 ofthe cartridge.

Patented March 9, 1971 3,568,600

INVENTOR.

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METHOD AND AFPPTHJS FOR CHIECG mo PRESSURE Oh AMMUNTTION BACKGROUND OF THE INVENTION This invention relates to methods and apparatus for deter mining the correct amount of powder that should be loaded into firearm cartridges to produce safe firing pressures.

has always been difiicult for sportsmen who are interested in reloading spent firearm cartridges to accurately determine the maximum amount of powder that should be loaded in the cartridges to produce efficient tiring pressures without exceeding the safe limit of the cartridge. It is well known that the type of the primer, the type and size of the cartridge, the style of the bullet and the particular powder lot are all important factors that bear on the amount of the powder that should be added to provide efficient and safe working pressures. One combination may produce a safe load while another combination may produce a dangerous load. Many accidents have occurred because the sportsman was unable to determine the correct amount of powder to reload spent cartridges.

One of the objects of this invention is to provide a method and apparatus for determining the correct amount of powder that should be loaded in spent cartridges upon reloading.

An additional object of this invention is to provide such an apparatus and method that may be readily used by sportsmen without requiring elaborate and expensive test equipment.

A further object of this invention is to provide a pressure indicator for mounting to the side of the cartridge for measuring the explosive pressure on the interior of the cartridge during firing without having to puncture the wall of the cartridge.

An additional object of thisinvention is to provide a deformable object that may be seated in the wall of a cartridge for generating an indication of the magnitude of the pressure on the inside of the cartridge during firing.

A still further object of this invention is to provide a small disc that may be inserted between the cartridge case and the tiring chamber of the firearm to gauge the pressure during firing.

These and other objects and advantages of this invention will become apparent upon the reading of the following detailed description of a preferred embodiment.

BRIEF DESCRIPTION OF THE DRAWINGS A preferred embodiment of this invention is illustrated in the accompanying drawings, in which:

FlG. l is a plan view of a test cartridge incorporating the principle features of this invention particularly emphasizing the placement of a thin metal disc in the side of the cartridge;

hi6. 2 is a plan view of the thin metal disc;

FIG. 3 is a side elevational view of the thin metal disc;

FlG. d is a side elevation of the thin metal disc showing the thin metal disc formed to complement the curvature of the wall of the cartridge;

FIG. 5 is a schematic cross-sectional view showing the test cartridge, with a bullet mounting therein, positioned in a firing chamber prior to detonation; and

Fit}. 65 is a fragmentary schematic view similar to FIG. 5 except showing the cartridge after it has been detonated emphasizing the deformation of the thin metal disc.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1 there is shown a test cartridge that has a forward neck section 13 for receiving a bullet and a flared shoulder section l2 extending to a tubular wall 13. The rear end of the cartridge is enclosed by the base i4 containing a primer.

The test cartridge has a pressure indicator for gauging the interior pressure during tiring. The pressure indicator includes a localized wall segment in with a deformable portion 17 that is recessed inwardly from the outer surface of the tubular wall.

The deformable portion 17 has a thickness less than the surrounding portion of the wall segment 116. The deformable portion 17 is calibrated to deform a prescribed amount when the interior pressure on the cartridge approaches the maximum safe limit of the cartridge.

As shown in the drawings, the localized wall section includes two elements or thicknesses-an indented wall member l? and a thin disc 20. The indented wall member 18 is a continuous segment of the cartridge wall that has been indented a prescribed amount to form a circular cavity 19 for receiving the disc 20. The disc 20 is made from a mild steel. The disc 20 is seated in the cavity l9 so that the outer surface 21 of the disc is flush with and conforms with the outer surface of the tubular wall 13. The disc 20 has a deformable circular center section 22. The circular center section 22 is recessed a predetermined distance so that the amount of subsequent bulge or deformation will be indicative of the interior firing pressure exerted on the cartridge. The disc 20 has an inner surface 23 with beveled edges so that. when the disc is seated in the cavity 19 it will not puncture the wall member 18 of the cartridge. Initially the disc is formed as shown in FIG. 2 and 3 with the circular center section having a flat-bottomed recess. The disc 20 is then curved as shown in FIG. 4 to conform to the curvature of the tubular wall 13 so that when the disc is seated in the indentation 19 the outer surface 21 of the disc 20 will be flush with the outer surface of the tubular wall 13.

To determine the correct amount of powder that should be added to the cartridge to provide a maximum safe firing or working pressure for a particular type cartridge, a test cartridge 10 is initially loaded with an amount of powder believed to be less than the amount that will produce the maximum safe pressure. A bullet 25 is then mounted in the neck portion of the cartridge. The cartridge 10 with the bullet is loaded in a firing chamber 26 having an interior wall 27 that conforms to the outer surface of the cartridge as shown in FIG. 5. If the amount of powder added to the cartridge is less than that which will produce the maximum safe working pressure, then the deformable portion 17 which includes the circular center section 22 of the disc will only partially bulge without engaging the inner wall 27 of the firing chamber 26.

Additional amounts of powder are added to the cartridge l0 until the deformable portion l7 will bulge outwardly to make contact with the interior surface 27 of the firing chamber to form a small flat segment on the bulge. When the cartridge is removed from the firing chamber, the small flat segment may be readily visually observed indicating that the correct amount of powder was added to the cartridge.

If an excess amount of powder is added to the cartridge the deformable portion 17 will deform to such a point that a very large flat area will be formed on the bulge.

Through a trial and error method, by successful loading and detonating gradually increasing amounts of powder in the car tridge, one can visually determine when the correct amount of powder has been added to the cartridge.

It is desirable that the discs 20 be as small in diameter and as thin as possible in order to not displace any more of the combustion volume of the cartridge than is necessary. It has been found that a disc of approximately five-sixteenths of an inch in diameter and having a thickness of 0.035 in. is particularly suitable for medium to large cartridges. The circular center section is initially formed with a Vs-inch-diameter indentation that is 0.015 in. deep having a flat bottom.

It is also important that the wall segment 16 be located in an area of the tubular wall that has a uniform thickness in strength.

if a sportsman desires to determine the correct amount of powder to be added to a particular type and model of cartridge, he first determines the maximum safe working pressure of the cartridge. This information is readily available from the manufacturer. The sportsman then purchases discs 20 that are calibrated for that particular working pressure. For example, if a particular type of cartridge has a maximum safe firing rating of 40,000 psi. then the sportsman will purchase discs that are calibrated for 40,000 p.s.i. The sportsman makes a cavity 19 in a spent cartridge. The disc is seated in the cavity to form r test cartridge. The sportsman then starts out with a reduced load and works up a grain or two at a time during each loading and firing until the bulge of the circular center 22 makes contact with the interior wall of the firing chamber 26. He will then know that the components he is using in this particular rifle or firearm are within the safe limits of the 40,000 psi. category.

It should be understood that the above described embodiment is simply illustrative of the principles of this invention and that numerous other embodiments or modifications may be readily devised without deviating from the principles thereof. Therefore, only the following claims are intended to define this invention.

I claim:

1. A test cartridge for determining the correct amount of powder that should be loaded in selected cartridges to produce a safe firing pressure, said test cartridge comprising:

a cartridge having a tubular wall with a wall section which has a deformable portion thereof that is recessed inward so that when the test cartridge is subjected to said safe firing pressure the deformable portion will deform outward a predetermined amount; and

the wall section including a thin metal disc that is seated in the side of the tubular wall without puncturing the tubular wall, said disc having a recessed center section with a reduced thickness.

2. A test cartridge as defined in claim 1 wherein the disc is produced from uniform mild steel.

' 3. A test cartridge as defined in claim 1 wherein the disc is seated in the tubular wall so that the outer surface of the disc is flush with the outer surface of the tubular wall.

4. A test cartridge as defined in claim 1 wherein the disc has a thickness of approximately 0.035 in. and the center section is recessed approximately 0.015 in. v

5. A pressure indicator for mounting to the sidewall of a firearm cartridge to determine the correct amount of powder to be loaded in the cartridge to produce a safe firing pressure, said pressure indicator comprising a thin metal disc seated in the sidewall of the cartridge flush with the outer surface of the sidewall, said thin metal disc having a deformable center section with a reduced thickness that will deform a predetermined distance when the cartridge is subjected to the selected safe firing pressure.

6. A pressure indicator as defined in claim 5 wherein the deformable center section of the disc is recessed below the outer surface of the cartridge sidewall a distance equal to the predetermined distance so that the central section will deform when subjected to the safe firing pressure.

7. A method of determining the correct amount of powder that should be loaded into tubular walled firearm cartridges to produce a safe firing pressure, said method comprising the steps of:

a. seating a test element in the exterior of the cartridge wall conforming with the exterior shape of the wall in which the test element has a deformable section that is recessed inwardly a predetermined distance so that when the safe firing pressure is exerted on the interior of the cartridge the deformable section will deform outwardly the predetermined distance; and

b. successively loading and detonating gradually increasing amounts of powder in the cartridge until it can be visually observed that the recessed section has deformed outwardly the predetermined distance.

8. A method as defined in claim 7 wherein a shallow cavity is first formed in the cartridge wall to receive the test element which is a thin metal disc having a recessed center section with a reduced thickness that is calibrated to deform the predetermined distance when the safe firing pressure is exerted'on the interior of the cartridge.

9. A method as defined in claim 8 wherein the cartridge is positioned in a firing chamber for detonating so that when the safe firing pressure is exerted on the interior of the cartridge the recessed section will deform outwardly making contact with the firing chamber.

Claims (9)

1. A test cartridge for determining the correct amount of powder that should be loaded in selected cartridges to produce a safe firing pressure, said test cartridge comprising: a cartridge having a tubular wall with a wall section which has a deformable portion thereof that is recessed inward so that when the test cartridge is subjected to said safe firing pressure the deformable portion will deform outward a predetermined amount; and the wall section including a thin metal disc that is seated in the side of the tubular wall without puncturing the tubular wall, said disc having a recessed center section with a reduced thickness.

2. A test cartridge as defined in claim 1 wherein the disc is produced from uniform mild steel.

3. A test cartridge as defined in claim 1 wherein the disc is seated in the tubular wall so that the outer surface of the disc is flush with the outer surface of the tubular wall.

4. A test cartridge as defined in claim 1 wherein the disc has a thickness of approximately 0.035 in. and the center section is recessed approximately 0.015 in.

5. A pressure indicator for mounting to the sidewall of a firearm cartridge to determine the correct amount of powder to be loaded in the cartridge to produce a safe firing pressure, said pressure indicator comprising a thin metal disc seated in the sidewall of the cartridge flush with the outer surface of the sidewall, said thin metal disc having a deformable center section with a reduced thickness that will deform a predetermined distance when the cartridge is subjected to the selected safe firing pressure.

6. A pressure indicator as defined in claim 5 wherein the deFormable center section of the disc is recessed below the outer surface of the cartridge sidewall a distance equal to the predetermined distance so that the central section will deform when subjected to the safe firing pressure.

7. A method of determining the correct amount of powder that should be loaded into tubular walled firearm cartridges to produce a safe firing pressure, said method comprising the steps of: a. seating a test element in the exterior of the cartridge wall conforming with the exterior shape of the wall in which the test element has a deformable section that is recessed inwardly a predetermined distance so that when the safe firing pressure is exerted on the interior of the cartridge the deformable section will deform outwardly the predetermined distance; and b. successively loading and detonating gradually increasing amounts of powder in the cartridge until it can be visually observed that the recessed section has deformed outwardly the predetermined distance.

8. A method as defined in claim 7 wherein a shallow cavity is first formed in the cartridge wall to receive the test element which is a thin metal disc having a recessed center section with a reduced thickness that is calibrated to deform the predetermined distance when the safe firing pressure is exerted on the interior of the cartridge.

9. A method as defined in claim 8 wherein the cartridge is positioned in a firing chamber for detonating so that when the safe firing pressure is exerted on the interior of the cartridge the recessed section will deform outwardly making contact with the firing chamber.

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