Centerfire Cartridge Primer Safety Shield
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.
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 INVENTIONThe 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 INVENTIONThe 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.
Referring now to
Cartridge B of
Cartridge C of
As shown in
Referring now to
Referring now to
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
- said washer having a thickness sufficient to withstand rifle impacts as set forth in claims 6 and 7.
10. 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 cup like about the exterior surface of said primer and having a central hole in the bottom 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 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;
- said central hole having a diameter less than the tip diameter of the projectile to be used in the firearm cartridge.
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.
Type: Application
Filed: Jun 25, 2010
Publication Date: Dec 29, 2011
Inventor: William S. DeHimerRome (Rome, NY)
Application Number: 12/824,055