US20110315038A1

US20110315038A1 - Centerfire Cartridge Primer Safety Shield

Info

Publication number: US20110315038A1
Application number: US12/824,055
Authority: US
Inventors: William S. DeHimerRome
Original assignee: Individual
Current assignee: Individual
Priority date: 2010-06-25
Filing date: 2010-06-25
Publication date: 2011-12-29

Abstract

A centerfire cartridge with improved ballistic characteristics for use in lever action firearms having tubular magazines is shown. A primer safety shield allows a sharper pointed bullet to be used without increased danger of inadvertent firing when a cartridge is placed in nose to base contact in a magazine.

Description

FIELD OF INVENTION

This invention relates to firearms ammunition and more particularly to rifle and pistol centerfire cartridges for use in magazines where the cartridge primer may come in contact with the tip of adjacent cartridges.

BACKGROUND OF INVENTION

The background of the firearms ammunition industry problems and challenges addressed in part by the present invention is set forth in great detail in the specification of U.S. Pat. No. 7,380,502 and is copied in part herein.
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 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. Centerfire cartridges have primers centered in the base of the cartridge and it is essential to ensure that the nose of one bullet does not act as a firing pin and strike the primer of the next cartridge. Traditionally this has required the use of blunt nosed bullets having diameters greater than the diameter of the centerfire primer to ensure any force transmitted to the primer is distributed over a large enough area to ensure that primer discharge will not occur.
Unfortunately flat or blunt nose bullets are aerodynamically inefficient compared to pointed bullets used in other types of rifles. This means that they lose more velocity as a function of distance traveled than a sharp pointed bullet resulting in less energy downrange and increased errors requiring shooter adjustment. A ballistic coefficient (BC) of 0.200 depending on caliber and weight of the bullet is common for blunt nosed bullets while BC values of 0.250 to 0.350 are achieved with comparable sharp nosed bullets. Translated into hunting values a lever action rifle is considered effective to about 100-150 yards while spire point bullets of comparable weight and muzzle velocities are effective beyond 250 yards.

SUMMARY OF PRESENT INVENTION

The present invention overcomes the flat nose bullet limitations of tubular type magazines such as the lever action rifle tubular magazines described in the referenced patent by providing a centerfire firearm cartridge with a safety shield about the primer such that the bullet fixed in such a cartridge may be more pointed than the traditional blunt nose bullets and substantially achieve the greater ballistic coefficients of more sharply pointed cartridges such as shown in the referenced US patent. By shielding the primer with a safety shield having a small central hole just large enough to admit a firing pin blunt nose bullets are no longer required to prevent unintended discharge of the primer and cartridge.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional side view of cartridges in a tubular magazine according to the present invention.

FIG. 2 is a sectional view of three cartridges with A showing a prior art cartridge, B showing a modified case with large rifle primer and safety shield; and C showing a standard case with small primer and safety shield. according to the present invention;

FIG. 3 is a sectional view of a small primer A, safety shield B, and assembly C;

FIG. 4 is a view similar to FIG. 3 with a large primer A, safety shield B, and assembly C;

FIG. 5 is a sectional view of a cartridge case showing another embodiment of my invention;

FIG. 6 is a view similar to FIG. 5 showing a still further embodiment of my invention.

DESCRIPTION OF PREFERRED EMBODIMENT

Referring now to FIG. 2 cartridge A is a cross section of a conventional center fire cartridge body 10 standardized one hundred years or so ago. Millions and millions of this type of cartridge body have been made and many are still available for reloading with a new large primer 12, powder and bullet of choice. Regardless of the caliber of the cartridge the diameter of the large primer has stayed at 0.212 inches and it has been made of cartridge brass that may be easily indented to compress the primer mixture against an anvil to fire the cartridge.
Cartridge B of FIG. 2 is a cross section of a first embodiment of my invention where a large primer 12 has been press fitted into a safety shield 14. Shield 14 is cup shaped and has a center hole 16 in the base. Hole 16 must be large enough to admit the firing pin but small enough to exclude the more pointed tip of the bullet to be used in the cartridge. A range of 0.060-0.110 inches, depending on the diameter of the bullet tip, seems to be satisfactory. In a preferred embodiment a diameter of 0.100 inches has been found to be suitable. A typical shield 14 might have an outside diameter of 0.266 inches. Shield 14 is preferably made of nickel plated steel with a thickness sufficient to prevent firing of the primer by recoil or other shock. The assembled shield 14 and primer 12 are press fitted into an appropriately enlarged cavity in the base of the cartridge 10′. While this would require modification of existing cartridge bodies and changing of the primer cavity dimensions in new manufacture the existing large primers could still be used.
Cartridge C of FIG. 2 shows a variation of my invention in which the large primer cavity diameter of 0.212 inches is maintained in the cartridge body 10″ and a smaller safety shield 18 is used to protect a “small” primer 20 which usually has an outside diameter of 0.175 inches. Again shield 18 has a center hole 22 with a diameter of 0.100 inches an inside diameter of 0.175 inches and an outside diameter of 0.212 inches. These dimensions allow the primer 20 to be press fitted into the shield 18 and the assembly press fitted into the large primer cavity in the standard cartridge body. Shield 18 is preferably made of nickel plated steel with sufficient strength so the thinner wall will still protect the primer from firing. It may be seen that in cartridge C the height of small primer 20 may be shorter than standard since safety shield 18 is sized to just fit in the large primer cavity in standard cartridges.
As shown in FIG. 1 the foregoing safety shields 14 and 18 prevent pointed bullet nose 24 from contacting the primer of the bullet in front of it. Obviously the bullets will not always be in perfect alignment as shown in FIG. 1 but when skewed there is even less possibility of contact with the primer.
Referring now to FIG. 3 a small primer cup 26 is shown with safety shield 28 sized to receive cup 26 in a press fit and the complete assembly staying within the outside diameter of 0.212 inches to allow press fitting in the standard cartridge body primer cavity. With this configuration of my invention the millions of existing cartridge shells can be reloaded using standard readily available parts and tools. Also new cartridges made with this safety shield may be used in lever action rifles with tubular magazines without sacrificing any appreciable accuracy or range with safety equal to or better than blunt nose bullets.
Referring now to FIG. 4 a primer safety shield for the large primer with its 0.212 inch outside diameter and 0.118 inch depth. Here typically the safety shield would have an outside diameter of 0.266 inches and an overall depth of 0.145 inches. While this would require resizing the primer cavity in the standard cartridge, for some applications it may be preferable to the configuration of FIG. 3.
FIG. 5 shows another embodiment of the invention in which the safety shield takes the form of a nickel plated steel flat washer 30 with a center hole of 0.100 inches press fitted into the base of the cartridge below the primer 32. This configuration gives the same protection and performance advantages as the foregoing alternatives although requiring some additional modification to the standard cartridge cases.
FIG. 6 shows a still further embodiment in which a nickel plated washer 34 having a central hole of 0.100 inches diameter and an outer diameter matching the primer 36 used in the primer cavity of the cartridge. It is affixed to the primer 36 before press fitting the assembly into the cartridge body. Safety shield washer 34 may be epoxyed, welded or otherwise affixed to the primer bottom.
While there are given above certain specific examples of this invention and it application in practical use, it should be understood that they are not intended to be exhaustive or to be limiting of the invention. On the contrary these illustrations and explanations herein are given in order to acquaint others skilled in the art with this invention and the principles thereof and a suitable manner of its application in practical use.

Claims

1. A firearm cartridge comprising:

an elongated cylindrical case defining an interior volume containing gunpowder having a rear end including a central primer pocket receiving a primer and a primer safety shield member and a forward end opposite from the rear end of the case for receiving therein a bullet;

said primer safety shield member being formed about at least the exterior surface of said primer and having a central hole in the surface thereof;

said primer safety shield having a diameter less than the diameter of said elongated cylindrical case and substantially greater than the diameter of a firing pin of a firearm;

a bullet received in said forward end of said elongated cylindrical case;

said bullet having a rigid tapered forward nose portion with a diameter less than said primer safety shield member diameter; and

said safety shield member central hole having a diameter less than the diameter of said tip of said bullet tapered forward nose portion.

2. The firearm cartridge of claim 1 wherein said safety shield member is cup shaped and said central hole has a diameter between 0.060 and 0.110 inches.

3. The firearm cartridge of claim 2 wherein said safety shield member central hole has a maximum diameter of 0.100 inches.

4. The firearm cartridge of claim 3 wherein said bullet tapered nose portion has a diameter of at least 0.110 inches.

5. The firearm cartridge of claim 1 wherein said primer safety shield member comprises an outer nickel plated steel cup member press fitted about said primer and inserted in the base of said elongated cylindrical case.

6. The firearm cartridge of claim 1 wherein said safety shield member comprises a steel cup press fitted about said primer having a central hole in the base thereof with a diameter of less than 0.101 inches and a thickness sufficient to support the impact of a column of firearm cartridges in a tubular rifle magazine without detonation of the primer in said safety shield member when the rifle is dropped butt first from a height of at least fifteen feet.

7. The firearm cartridge of claim 1 wherein said safety shield member comprises a steel cup press fitted about said primer having a central hole in the base thereof with a diameter of less than 0.101 inches and a thickness sufficient to support the impact of a column of firearm cartridges in a tubular rifle magazine without detonation of the primer in said safety shield member under heavy recoil.

8. The firearm cartridge of claim 1 wherein said safety shield member is a washer having a central hole of less than 0.101 inches secured in the bottom surface of said elongated cylindrical case; and

said washer having a thickness sufficient to withstand rifle impacts as set forth in claims 6 and 7.

9. The firearm cartridge of claim 1 wherein said safety shield member is a washer having a central hole of less than 0.101 inches secured to the bottom surface of said primer; and

10. A firearm cartridge comprising:

said primer safety shield member being formed cup like about the exterior surface of said primer and having a central hole in the bottom thereof;

a bullet received in said forward end of said elongated cylindrical case;

said bullet having a rigid tapered forward nose portion with a ballistic coefficient of greater than 0.250; and

said safety shield member central hole having a diameter less than the diameter of the tip of said bullet tapered nose portion.

11. A firearm cartridge component comprising;

a cylindrical cup body open at the top;

said body bottom having a central hole;

said central hole having a diameter less than the tip diameter of the projectile to be used in the firearm cartridge.

12. A firearm cartridge component as claimed in claim 11 wherein said cup body has an outer diameter equal to the large primer diameter and an inner diameter equal to the outer diameter of a small primer.

13. A firearm cartridge component as claimed in claim 11 wherein said body has an inner diameter equal to the outer diameter of a large primer and an outer diameter less than the cartridge body diameter.

14. A firearm cartridge component comprising:

a cylindrical flat body portion;

said body portion having a central hole;

15. A firearm cartridge component as claimed in claim 14 wherein said flat body portion has an outer diameter equal to the primer diameter.

16. A firearm cartridge component as claimed in claim 14 wherein said flat cylindrical body portion has an outer diameter greater than the primer diameter.