US3057264A - Projectile broach - Google Patents

Description

C W. MUSSER PROJECTILE BROACH Filed May 20, 1960 INVENTCR. C WALTON MUSSER Q. JQ M M BY ijfloimii ATTORNEYS Oct. 9, 1962 United States Patent Ofiice 3,057,264 Patented Oct. 9, 1962 3,057,264 PROJECTILE BROACH C Walton Musser, Beverly, Mass, assignor to the United States of America as represented by the Secretary of the Army Filed May 20, 1960, Ser. No. 30,692 1 Claim. (Cl. 90-63) (Granted under Title 35, US. Code (1952), see. 266) The invention described herein may be manufactured and used by or for the Government for governmental purposes without the payment to me of any royalty thereon.

This invention relates to the manufacture of firearms, and more particularly to a device which functions in response to the firing of an explosive charge to rifle the interior of a gun barrel.

Heretofore the rifiing of a gun barrel has usually involved the use of a cutting tool fixed to the end of an arm adapted to be extended into the bore of the gun. The present invention simplifies and greatly expedites this procedure by the provision of an improved rifle cutting device which functions in response to the firing of an explosive charge. In a preferred embodiment of the invention, [the cutting element of the device is in the form of a projectile having a cylindrical forward portion which is a close fit to the barrel and a rearward portion provided with cutting teeth having a lead designed to give the desired twist to the rifling.

The invention will be better understood from the following description when considered in connection with the accompanying drawings and its scope is indicated by the appended claim.

Referring to the drawings:

FIG. 1 shows a longitudinal section of a gun containing a projectile and cartridge case according to this invention.

FIG. 2 is a longitudinal section through the projectile alone.

FIG. 3 is an enlarged longitudinal section of the cutting teeth.

FIG. 4 is a top plan developed view showing a rear portion of the lead and teeth of FIG. 3.

FIGS. 1 to 3 illustrate a conventional recoilless rifle which includes a barrel 10, a chamber 11 and venturi 12. Extending through the chamber 11 is a cartridge which includes a casing 13 enclosing an explosive charge and a projectile 14. This projectile has walls of about the wall thickness of a recoilless rifle lbarrel as shown in the herein drawing.

The projectile 14 has on its rearward surface teeth 15 (FIGS. 1, 2 and 3) which are similar to the teeth of a broach and have a lead designed to give a desired twist to the rifiing. The forward surface of the projectile has no teeth and functions to guide the breach through the rifle tube.

In practicing the invention, the cartridge 13--14 is fired in the same manner as a conventional cartridge. The device is especially useful where a shallow-groove rifling is required to give a fin stabilized projectile a slight twist to prevent ya-w. An advantage in the illustrated construction is that the cutting teeth 15 are protected during shipment and handling by the cartridge case 13 which in usual practice is of a softer metal than the projectile itself. As shown, approximately the rear half and heavier duty part projectile teeth have a more rigid support than do the fore portions because these projectile teeth are located over and nearer the solid base of the projectile, while the fore portion of teeth 15 are radially outside a hollowed central portion. The close fitting cylindrical guide portion 16 of the projectile is advantageously close to the cutting teeth 15. The perforations in casing 13 are for the usual purpose for their use in recoilless weap ons, but here these perforations are located in rear of the cutting teeth, which teeth are protected by imperforate case material as shown.

I claim:

In a round for cutting rifling grooves in the barrel of a recoilless rifle for firing a fin and spin stabilized projectile, the combination therewith of the improvement adapting said cutting round for use in a recoilless weapon, said round comprising a projectile having an axial hollow portion having walls of about the wall thickness of a recoilless rifle barrel in which rifiing grooves are to be cut by firing said round, said hollow portion extending for a major portion of the length of said projectile from its front end, cutting teeth on approximately a rear half of the length of the projectile and extending over a solid base portion and forward thereof, a forward portion of said projectile being a guide of a size to closely fit within a barrel of a gun and be closely adjacent said cutting teeth to reduce the danger of any buckling occurring when a rifle groove cutter is being pushed, the cutting teeth having a lead for cutting rifiing grooves in a gun barrel with the teeth being of increasing diameter toward the rear, and said cutting round including a cartridge case of usual case material and having a forward imperforate portion covering said teeth with a perforate portion in rear of said projectile, to enclose a propellant charge.

References Cited in the file of this patent UNITED STATES PATENTS 37,898 Bonzano Mar. 17, 1863 599,472 Nobel Feb. 22, 1898 1,394,079 Fuchs Oct. 18, 1921 2,641,822 Sampson June 16, 1953 2,994,249 Schecter et al. Aug. 1, 1961

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