Integral Primer Cartridge

Abstract

A cartridge having a case with an anvil-less percussive ignition primer as an integral unitary part of the cartridge case, the case having a cup-shaped bore into which is compacted a primer mixture without an anvil.

Parent Case Text

This is a continuation, division of application Ser. No. 103,237 filed Dec. 31, 1970, now abandoned.

Description

This invention relates to a cartridge having a percussive primer formed integrally therewith.

In conventional percussion fired cartridges a separately formed percussive primer is secured as a unit, as by a friction fit, within a rearwardly open primer-receiving bore formed in the cartridge case and communicating with a further enlarged bore formed in the case and containing propellant powder. While this conventional cartridge construction is quite satisfactory from an operational standpoint, such requires separate manufacture of both the cartridge case and the percussive primers, as well as sealing of the primer in the cartridge case, and in addition the percussive primers conventionally employ a construction having an anvil formed as a part thereof, which further adds to the construction requirements and expenses of construction.

It is an object and feature of this invention to provide a cartridge of considerably less complexity and of less cost to manufacture, through the provision of a cartridge case having a percussive primer formed integrally therewith.

It is still a further feature of the invention to provide a cartridge having a percussive primer as an integral part of the cartridge case, and in which the primer is devoid of an anvil in the normal sense of the word as applied to percussive primers.

Still other objects, features and attendant advantages will become apparent to those skilled in the art from a reading of the following detailed description of a preferred embodiment constructed in accordance with the invention, taken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a longitudinal section view of a cartridge according to the invention, the cartridge being shown in chambered position in a barrel, in readiness for firing.

FIG. 2 is a fragmentary view of the arrangement of FIG. 1, schematically showing the firing of the cartridge by a firing pin according to the invention.

Referring now in detail to the figures in the drawings, an illustrative cartridge 11 according to the invention has a case 13, within the open forward end of which is secured a projectile 19 of any suitable form or construction, as by annular crimping as indicated at 17b. In this respect, while the invention is illustrated with respect to a single projectile, it will be apparent that the invention is equally applicable to multiple projectile cartridges, including shotgun cartridges, as well as to blank cartridges in which there is no projectile as such but only an ignitable charge of propellant or other desired ignitable powder.

Case 13 includes a base 15, and a forward bore section 17. The case may be externally formed in any desired general configuration, so as to fit within a desired barrel chamber, and the projectile or projectiles may be fired to pass through a smooth bore or rifled barrel.

The forward bore section 17 of the case 13 has an internal cylindrical bore 17a formed therein, in which is disposed a propellant charge of suitable composition, and which may be of convention composition for flash ignition by percussive ignition primers. The base 15 has formed therein a cup-shaped cylindrical bore bounded along its length by a cylindrical wall 15b, and its base by the forward wall surface 15c" of an integral web 15c of the case base 15, the rear surface of the web 15 being indicated at 15c' and being a central extension of the rear surface of base 15, against which rear surface a breech bolt 33 and firing pin 31 may be brought to bear for firing of the cartridge through firing of a primer mix disposed within the integral primer bore 15b. The cup-shaped bore 15b perferably has a length greater than its diameter, although this is not necessarily required in all constructions for operation.

Compacted within the bore 15d is a primer charge 17 which may be of generally conventional composition and desirably contains a mixture of grit or abrasive which is preferably as exothermic fuel, so as to enhance the firing reliability. The degree of compaction of the primer charge 17 is variable, but desirably it should be as great as possible without resulting in accidental ignition during the manufacture of the cartridge. The primer charge 23 contained in the bore 15b primer cavity is separated from the propellant 21 contained in the larger diameter bore 17a of the forward section 17 of bore 15b by a thin easily frangible, and preferably combustible,moisture seal 25 of suitable material, such as a coating of wax or Krylon. While the moisture seal 25 is not absolutely required for functional operation, it is desirable to aid against malfunction due to undesired moisture absorption by the primer charge 23 which, for example, might occur during assembly.

A primer is thus effectively formed integral with the cartridge case 13, and percussive ignition of the primer is effected by percussively impacting and indenting the flat exterior surface 15c" of the weapon 15c, through the medium of a firing pin 31 having a relatively wide blunt nose protrusion 31b formed thereon, as indicated in FIGS. 1 and 2. Percussive ignition of the primer charge in turn effects flash firing of the propellant charge 21, to thereby create the necessary gas pressure for propelling the projectile 19 from the cartridge case 13 and along the bore of the barrel 41.

The exact manner in which the primer charge 23 is ignited without the requirement for an anvil is not fully understood, but it is thought that the indentation formed in the relatively thin-walled web 15c of the case 13 causes primer ignition through imparting relative movement between particles in the primer charge 23, as by causing a column of primer charge particles in the cylindrical bore cavity 15b to move in relation to other primer charge particles nearer the periphery of the cylindrical bore cavity 15b which remain generally stationary due to the friction between the primer charge 23 and the cylindrical bore wall 15b, and that the resulting abrupt friction between the moving and stationary primer charge particles generates a sufficient heat to ignite the primer charge 23, or as by abrupt relative motion and compaction of a quantity of primer particles at the rear end of the primer charge cavity adjacent web 15c, with these rear centrally disposed particles being moved in compaction against the restraint exerted by the remaining forward mass of primer charge particles in the highly compacted columnar mass 23 of primer charge particles. However, irrespective of the theory by which the primer charge 23 is ignited, the anvil-less ignition of the primer charge 23 ruptures the moisture seal 25 and fires the propellant 23 which generates a high gas pressure that propels the projectile 19 forward through the barrel bore.

Since a sufficient indentation must be made in the web 15c of case 13 to ignite the primer charge 23, yet not exceed the elongation or shear limits of the case material, the contour of the protrusion 31b formed on the head 31a of the firing pin 31 is of importance. The diameter and the amount of the protrusion formed on the surface of the head must be sufficient to cause adequate compacting or internal relative movement of the primer charge particles within the cavity 15d to cause ignition of the primer charge, yet the annular edges or corners such as at 31c, 31d on the protrusion 31b should be rounded or chamfered to prevent shearing failures of the relatively thin primer web 15c. Also, the diameter of the head 31a of the firing pin 31b extends across an extent of the rear face of the cartridge case 13 laterally beyond the zone of web 15c to provide an adequate impact support for the web 15c to prevent impact shearing by the pin, and upon ignition, possible rupture by the resultant high pressure propellant gas.

The integral primer cartridge case 13 may be suitably formed of various materials, dependent upon the tensile strength required. For peak propellant burning pressures of the order of approximately 50,000 - 70,000 psi high tensile strength steel such as medium to high carbon steel (e.g., 1050 steel, 1065 steel), heat treatable alloy steels and precipitation hardening steels, are suitable. For lower peak propellant pressures as of the order of 40,000 psi or less, the integral primer cartridge case 13 may be formed of brass or other material of lower tensile strength properties.

In one illustrative mode of practicing the present invention, an integral anvil-less primer cartridge case 13 is formed from standard cartridge brass, having a primer bore 15b of 0.093 inch, and a web 15c thickness of approximately 0.014 inch. Inside the primer bore cavity, 0.04 grams of dried primer charge are compacted with a pressure of the order of from 125,000 to 175,000 psi, and the length/diameter ratio of the cylindrical primer charge 17 is in the range of approximately 1.5 to 2.0. An illustrative and preferred embodiment primer composition consists of the following ingredients in the indicated proportions:

EXAMPLE I

Ingredient % Dry Wt. Lead Styphnate, Normal (sensitive high explosive) 37 .+-. 5 Tetracene (sensitive high explosive) 4 .+-. 1 Barium Nitrate (oxidizer) 32 .+-. 5 Antimony Sulfide (abrasive & exothermic fuel) 15 .+-. 2 Aluminum Powder (exothermic fuel) 7 .+-. 1 PETN (Class 2) (high energy yield high explosive) 5 .+-. 1

This is a composition now generally known as FA-956, except that it does not include a light gum solution which is normally utilized in FA-956 per se.

An alternative workable composition is as follows:

EXAMPLE II

Ingredient % Dry Wt. Lead Styphnate, Normal (sensitive high explosive) 31 Barium Nitrate (oxidizer) 19 Antimony Sulfide (abrasive & exothermic fuel) 20 Lead Dioxide (oxidizer) 8 Tetracene (sensitive high explosive) 10 Zirconium (catalyst) 8 PETN (Class 2) (high energy yield high explosive) 4

With the foreging described illustrative example, the associated firing pin used in conjunction with the cartridge may satisfactory impact the web 15c with an input energy of 48 inch-ounces, and have a diameter of 0.155 inch with a protrusion extending approximately 0.012 inch from the head of the firing pin and with a diameter of 0.060 inch. In this example, the base radius of curvature 31d of the protrusion 31b on the firing pin 31 is 0.020 inch, while the radius of curvature at the extended rim surface 31c of the protrusion is 0.005 inch.

While the invention has been illustrated and described with respect to a single preferred embodiment, it will be apparent to those skilled in the art that other embodiments and various modifications and improvements may be made without departing from the scope and spirit of the invention. For example, the primer cavity formed in the cartridge case 13 by wall 15b of the integral anvil-less primer may not necessarily be cylindrical but may assume a variety of cross-sectional shapes. Also, the moisture seal need not be combustible but may be of very thin, relatively non-combustible, easily frangible material such as Chapman's red lacquer, epoxy or metal foil which offers substantially no resistance analogous to or which in any substantial manner would function an anvil for the ignition of the primer charge. The composition of the primer charge may be varied to produce more, or less if desired, friction between the relatively moving particles of the primer charge. Accordingly, it is to be understood that the invention is not to be limited by the single preferred illustrative embodiment, but only by the scope of the appended claism.

Claims

That which is claimed is:

1. A cartridge arrangement comprising

a case having a primer-cup-forming case base and connecting extended side walls forming a cup having a main cup-shaped case cavity for containing propellant powder,

a propellant charge disposed within said cup,

said case base being of one unitary integral piece and formed of malleable material and having a forwardly open cup-shaped primer-mix recess therein extending rearwardly from, and opening at its forward end into, said main cup-shaped case cavity,

said case base having a relatively thin impact-deformable malleable web forming the integral rear wall of said cup-shaped primer-mix recess,

and a columnar mass of percussively ignitable primer mix compacted within said cup-shaped primer-mix recess,

said cartridge being devoid of an anvil for said primer mix and devoid of any ignition assisting fracturable container therefor,

said impact-deformable integral web being deformable to effect firing of the primer mix without rupturing of such web, and maintaining its structural sealing integrity without rupture, upon firing of the primer and propellant charge.

2. A cartridge according to claim 1,

said case with its primer cup base and side walls being a unitary one piece elment,

3. A cartridge according to claim 1,

said primer mix having a frangible anvil-less covering thereon,

4. A cartridge according to claim 1,

said compacted primer mix comprising an explosive powder constituent, an oxidizer constituent, and an abrasive constituent.

5. A cartridge according to claim 4,

said primer mix further comprising a catalyst constituent for increasing the explosive reaction rate between said explosive powder and said oxidizer.

6. A cartridge according to claim 4,

said primer mix including abrasive particles.

7. A cartridge according to claim 6,

said abrasive particles being also ignitable and acting as an exothermic fuel.

8. A cartridge according to claim 1,

mass of primer mix being greater than its greatest cross sectional width.

9. A cartridge according to claim 8,

said columnar mass of primer mix being cylindrical, and the length of said columnar mass being substantially greater than the diameter thereof.

10. A cartridge arrangement according to claim 9,

and projectile means carried by said case adjacent the forward end of said case.

11. A cartridge arrangement according to claim 1,

and projectile means carried by said case adjacent the forward end of said case.

12. A cartridge arrangement according to claim 2,

and projectile means carried by said case adjacent the forward end of said case.