Jacketed-cast bullet

July 28, 1964

3,142,256

B. V. MACK

JACKETED-CAST BULLET Filed April 3, 1959

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BY.

ATTORNEY

United States Patent Office

3,142,256

Patented July 28, 1964

3,142,256 JACKETED-CAST BULLET

Bernhard V. Mack, Kensington, Calif.

(29 Kingston Road, Berkeley 7, Caiif.) Filed Apr. 3, 1959, Ser. No. 803,871

Claims. (CI. 102—92.5)

This invention relates to new versatile jacketed bullets for use in rifled firearms and more particularly to such new bullets which are particularly adapted for manufacture by a casting process.

Though equipment is available for the manufacture of extruded bullets, such equipment is very expensive and the extruding operation sufficiently exacting that the production of bullets by a casting process is often preferred. Bullets made in this manner have a cast portion made from a low melting metal such as lead or lead-base alloys, and the cast portion must extend continuously through the bullet in order for the bullet to be cast in one operation. The cast material should be exposed at the base of the bullet in order that the cast material may be introduced from the base of the bullet where there is a flat surface on the bullet where the sprue in the bullet mold can terminate.

It is well known that ordinary cast bullets having unprotected bases are capable of only limited velocities, i.e. maximum muzzle velocities of about 1500 feet per second. When sufficiently large powder charges are employed with these bullets in an attempt to produce greater velocities, serious problems are encountered; the hot low pressure gasses from the burning powder which initially pass around the base of the bullet cause serious softening and erosion, finning, of the lead at the periphery of the base of the bullet, and the bullet is distorted by frictional heating and erosion as it passes through the gun barrel. These problems result in deposition of lead in the gun barrel followed by distortion and loss of gyrostatic stability and accuracy of successive bullets fired through the barrel.

High bullet velocities are very desirable in order that the bullet may have a relatively flat trajectory and maximum kinetic energy and hence killing power. Accordingly it is conventional practice to attach to cast bullets flanged discs or cups made of higher melting metals such as gilding metal, brass or copper. These discs are called gas checks and fit over the heel of the bullet and protect the periphery of the base of the bullet from the action of the low pressure gasses of the burning powder. Gas checked bullets are capable of velocities slightly higher than those for unprotected cast bullets, i.e. maximum muzzle velocities up to about 2200 feet per second, but the gas checked bullets are limited in velocity by the frictional heating and erosion caused by passage of the bullet through the gun barrel.

Bullets capable of much higher muzzle velocities, average of 3000 and up to 4000 feet per second and higher, are made by enclosing a lead or lead-base alloy core of the bullet in a metal jacket made of a higher melting metal. The jacket covers the entire groove bearing surface of the bullet and hence eliminates the frictional heating, melting and erosion of the periphery of the bullet. Jacketed bullets for sporting and military purposes are made by placing a lead core, usually extruded lead wire, inside a preformed seamless cylindrical jacket having only one open end followed by a series of cold forming, shaping, extruding and sizing operations. However the jackets for these bullets are full jackets, i.e. jackets which enclose the entire bullet from the base side of the groove bearing surface forward over the entire groove bearing area and forepart of the bullet. The use of full jackets has been necessary on these bullets where the lead core is exposed at the base of the bullet because of the tendency of the lead core to be driven axially through the jacket when, in the gun barrel, the lead core is subjected to the thrust from the burning powder while the jacket 5 is subjected to frictional resistance to its passage through the gun barrel.

Because of this tendency of the lead core of a bullet to be driven through the jacket of the bullet when the lead core extends continuously through the bullet and is 10 exposed at the base and forepart of the bullet, it has been necessary to use jackets which completely enclose the base of the bullet when a jacket is desired on a mushroom type bullet such as commercially sold hollow point, soft nose, bronze pointed, open point expanding and metal 15 tipped hunting bullets. These mushroom type bullets cannot be manufactured by conventional casting methods because the material of the lead core is introduced into the jacket from the nose of the bullet where there is no flat surface on the bullet from which the sprue of a mold 20 can lead. Accordingly these bullets are conventionally made by introducing the material of the core into the jacket from the forepart of the bullet and then cold forming, shaping, extruding and sizing the core and jacket.

I have now devised a class of jacketed bullets which 25 have a heavy metal core extending continuously through the bullet from the base to the forepart of the bullet and exposed at the base and forepart of the bullet, the jacket carrying means for preventing the core from moving axially with respect to the jacket.

Preferably this means for preventing relative axial movement of the jacket and core is a portion of the jacket spaced axially from the base of the bullet and having a thickness greater than a part of the jacket which separates it from the base of the bullet. This thick por35 tion of the jacket grips the core and prevents the core from moving forward with respect to the jacket. Since the portion of the jacket has an increased thickness, its tendency to merely bend out of the way is overcome.

High muzzle velocities can be obtained with these bul⁴⁰ lets by increasing powder charges used with the bullet, and with a given powder charge the muzzle velocities can be increased by increasing the thickness or hardness of the jacket or by increasing the hardness of the lead base alloy of the core.

⁴⁵ With these bullets, muzzle velocities can be obtained which are equally as high as the muzzle velocities obtainable with conventional jacketed bullets yet my new bullets have exposed lead at the forepart of the bullet so that they can be used efficiently as mushroom bullets having excellent controlled expansion, and at the same time they have lead exposed at the base of the bullet and extending continuously through the bullet so that the bullets can be made efficiently in a simple one-step casting operation.

° The class of bullets of my invention are illustrated in the attached drawings in which:

FIG. 1 is a longitudinal sectional view of a bullet embodying the principles of my invention;

^FIG‘ ² ’^{S a lon}8‘^tudinal sectional view of another bullet embodying the principle of my invention and equipped with a flange for protecting the base of the bullet;

FIG. 3 is a longitudinal sectional view of a bullet similar to that illustrated in FIG. 2 but in addition provided with cannelures in the bullet for lubrication and cleaning ^J of the gun barrel and for crimping the bullet into a cartridge case.

FIG. 4 is a longitudinal sectional view of a bullet employing a preferred embodiment of my invention;

TIG. 5 is a longitudinal sectional view of the preferred bullet of my invention; and

FIG. 6 is a longitudinal sectional view of another bullet

3,142,256 embodying the principles of my invention and provided with an improved mushroom point and a boattail.

Referring now in detail to the drawings, the bullet illustrated in FIG. 1 comprises a central cast core 1 surrounded by a jacket 2. The jacket covers the entire 5 groove bearing area 3 of the bullet, the area of maximum diameter of the bullet, and the jacket 2 extends over a portion 4 of the forepart of the bullet. The jacket 2 carries a radially inwardly extending flange 5 which is imbedded in the core 1 and which is formed by bending the 10 jacket inwardly into· the core 1 and then outwardly back on itself. The forward surface 6 of the flange 5 is preferably slightly inclined to the axis of the bullet so that the surface 6 extends from the jacket 2 inwardly toward the axis of the bullet and slightly rearwardly toward the base 15 7 of the bullet; this slight inclination of the surface 6 prevents gas from being trapped in the bullet while the core 1 is being cast. The base 7 and the forward portion 8 of the core 1 are exposed.

The bullet illustrated in FIG. 2 comprises a cast core 20 1 and a jacket 2 which overlies the core 1 over the groove bearing portion of the bullet. The jacket 2 carries a rearward flange 9 which covers a portion of the base 7 of the core 1 and protects the peripheral edge 10 of the core 1 from the action of hot gasses in the gun barrel. 25 The jacket carries a forward flange 11 extending radially inwardly into the core 1 to prevent axial movement of the core 1 with respect to the jacket 2. The forward faces 6' and 6 of the flanges 9 and 11 respectively are inclined to the axis of the bullet to prevent entrapment of gas in 30 the bullet when the core is cast. The jacket 2 may be provided with one or more cannelures 12 which will collect foreign material in a gun barrel and which may be filled with a conventional lubricating composition, or may be employed for crimping a cartridge case to the bullet. 35 The deep cannelure 12' having generally radially extending sides also functions as flanges 11 to prevent relative axial movement of the jacket and core.

The bullet illustrated in FIG. 4 comprises a central cast core 1 and a jacket 2 which covers the entire groove 40 bearing area of the bullet. The jacket 2 is made up of a rearward jacket member 13 which carries on its base the flange 9 having surface 6'. The forward portion 14 of member 13 is constricted so that it has smaller inside and outside diameters than the remainder of member 13. A 43 second jacket member 15 overlies portion 14. The outer surfaces of members 13 and 15 lie on the same cylinder and comprise the groove bearing area of the bullet. When the bullet is driven through a gun barrel, the increased thickness of the jacket 2 where members 13 and ₅₀15 overlap prevents the core 1 from moving axially with respect to the jacket 2. Furthermore the frictional resistance to the bullet’s passage through a gun barrel will tend to seat the member 15 more firmly on the member 13; as a result, any flow of the material of core 1 out from 55 under member 13 responsive to the pressure of burning powder would permit member 15 to slide down and compress member 13 to again grip the core 1. Tnis action is further enhanced if the diameter of member 15 is made slightly larger than the diameter of member 13. The ex- ₆₀ternal groove 12 at the rearward end of member 15 functions as a cannelure similar to the cannelures 12 in FIG. 3. Member 15 may carry on its forward end, as illustrated in FIG. 5, a flange 11 and surface 6 to further prevent relative axial movement of core 1 and jacket 2 as _6gdid the corresponding parts in FIG. 2. The telescopic construction of the jacket illustrated in FIGS. 4 and 5 permits the use of one jacket for manufacturing bullets of varying length. As the bullet is made larger and the groove bearing area is lengthened, the jacket members can γθ be slightly separated.

The bullet of FIG. 6 comprises a cast core 1 encircled by a jacket 2 which carries a central flange generally indicated by 16 and the base flange 9. The jacket is in fact made of two juxtaposed members 17 and 18 carry- 75 ing flanges 19 and 2® respectively, and the flanges 19 and 20 combine to make up the flange 16. The bullet of FIG. 6 is also provided with a conventional boattail 21 which is covered by jacket 2.

The bullets of my invention may be easily modified so as to provide mushroom bullets for hunting purposes. Thus the bullet may be provided with a hollow point as indicated at 22 in FIG. 4 or a foreign object may be impregnated in the forepart of the bullet as indicated at 23 in FIG. 6. This latter expedient may be employed easily in bullets of my invention by placing a small piece of material such as lead shot in the bullet mold before the core 1 is cast. The lead shot must be heavier than the material of core 1 and must have a higher melting point than the material of core 1. The lead shot will rest in the bottom of the mold and thus become impregnated in the forepart of the bullet; when the bullet is subsequently fired and strikes an object, the shot will be flattened causing the forepart of the bullet to mushroom.

As stated above, the class of bullets of my invention have a central cast core and a metal jacket surrounding the core. The bullets are best produced by prefabricating the jacket, placing it in a mold where the base of the bullet is on top, and pouring the material of the cast core into the mold through the opening in the base of the jacket. The jacket should be made from a material having a melting point higher than the melting point of the material of the core so that the latter will not melt the jacket in the mold, and also because the jacket should have a higher melting point than the core in order for the jacketed bullet to be capable of higher muzzle velocities than an unjacketed bullet. The jacket is preferably made of a red or yellow brass, i.e. an alloy having from 95 to 64 weight percent copper and 5 to 36 weight percent zinc, or the jacket may be made of any other high melting material which is softer than the metal of a gun barrel and will slide on steel. The jacket can be made of a soft steel electroplated with copper. Most desirably the jacket is made of gilding metal. The cast core of the bullet may be made of any of the heavy, low-melting materials from which bullets may be cast; suitable materials for the core are lead and lead alloyed with tin and/or antimony.