US2397544A

US2397544A - Method of rifling

Info

Publication number: US2397544A
Application number: US502699A
Authority: US
Inventors: John C Garand
Original assignee: Individual
Current assignee: Individual
Priority date: 1943-09-16
Filing date: 1943-09-16
Publication date: 1946-04-02
Anticipated expiration: 1963-04-02

Description

April 9 I J. C. GARAND 2,397,544

METHOD OF RIFLING F iled Se t. 16, 1943 JWW JUHN E-GARAND,

Patented Apr. 2, 1946 UNITED STATES PATENT OFFICE METHOD OF RIFLING John C. Garand, Springfield, Mass. Application September 16, 1943,-Seriai-No. 502, 699

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 O. G. 757) 1 Claim.

' 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 a composite firearm barrel and to a method for forming the rifling in such barrel.

The conventional method of rifling a barrel for a firearm is to cut helical grooves in the barrel by broaching or by a cutter in a rifiing machine. Prior to machining a barrel blank the blank must be heat treated to obtain the desired physical properties of the finished barrel. Such heat treatment however generally does not improve the machlnability oi the blank. Machining operations on such a blank are extremely hard on the cutting tools thereby requiring frequent resharpening of such tools which adds materially to the cost of fabrication of a barrel and to the time required to produce the rifling therein. Further where difficult machining is encountered the surface of the bore of a barrel will invariably be rough. Such a rough surface invites corrosion due to the diiliculty in keeping the bore clean.

In addition firearm manufacturers have found that steels of the type known as stainless steels which are highly corrosion resistant are especially suitable for barrels for that reason. Steels of this class however have very poor machinability qualities which almost precludes their use for barrels when such barrels are fabricated by conventional methods.

Accordingly, it is an object of this invention to provide an improved firearm barrel and an inexpensive and rapid method for fabricating a firearm barrel and particularly for forming the rifling in such barrel.

It is a particular object of this invention to provide a method of rifiing a tube for a firearm barrel by the use of pressure to force the walls of the barrel tube into the grooves of a master form.

The specific nature of the invention as well as other objects and advantages thereof will clearly appear from a description of a preferred embodiment as shown in the accompanying drawing in which:

Fig. 1 is a perspective view of a portion of a barrel tube mounted on a grooved mandrel.

Fig. 2 is a cross-sectional view of the barrel tube and mandrel mounted between the rollers.

Fig. 3 is a cross-sectional view of the rifled tube assembled to a barrel jacket.

Fig. 4 is a partial longitudinal sectional view showing the barrel tube spun into the chamber of the barrel jacket.

Briefly, this invention comprises forcing a portion of the wall of a barrel tube into substantially helical grooves on a mandrel which is inserted within the barrel tube. The grooves on the mandrel, of course, conform to the twist of rifiing desired, The wall is forced into these grooves by rollers which bear against the outer surface of the tube directly opposite each groove as the tube and mandrel are drawn between the rollers on a helix conforming to that of the grooves.

There is shown in Fig. 1 a section of a barrel tube I and a portion of a mandrel 2 inserted within the barrel tube I. Four helical grooves 3 are exteriorly formed on mandrel 2. Any number of such grooves may be provided, however, the number shown serving only for illustration. The barrel tube I with mandrel 2 inserted within tube I is then arranged so that it may be drawn between four equally spaced oppositely disposed rollers 4 (Fig. 2). A suitable machine such as a planer (not shown) may be utilized to pull the barrel tube and mandrel assembly between the rollers 4, such machine to impart a helical motion to the barrel tube and mandrel assembly as it is drawn between rollers 4 so that the rollerswill depress the wall of the barrel tube. into grooves 3 in mandrel 2. It should be mentioned that the machine (not shown) must of course produce the same helical lead as that of the grooves 3 in mandrel 2.

It is desired to point out that the depth of the lands of a .30 caliber barrel is only .004 of one inch. Lands of larger caliber rifles are of course proportionately larger. It is thus readily apparcut that only a comparatively small amount of deforming is necessary to force the barrel tube into grooves 3 of mandrel 2. The rollers 4 are preferably made adjustable so that they may be moved nearer or farther away from the longitudinal axis of the barrel jacket as may be desired. Rollers 4 must, however, be set so that they will force the wall of barrel tube I to completely fill the grooves 3. Each roller 4 is, of course, mounted directly over each groove 3. The barrel tube and mandrel assembly is then drawn between the rollers 4 by the machine (not shown) employed. After the barrel tube has, been drawn through the rollers 4 mandrel 2 is removed from barrel tube I as by an arbor press and the bore of. such tube will then have integrally formed lands 5 as shown in Fig. 3. Slight depressions 6 will be formed on the outside of barrel tube I where the rollers 4 have come in contact with barrel tube I due to forcing the wall of the barrel tube I into grooves 3 of mandrel 2. It should be mentioned the propelling gases.

The comparatively thin barrel tube I may then be shrunk, sweated or forced into a barrel jacket I (Figs. 3 and f1). Barrel jacket'lis of con- I I been metho'dewililikewfise'sbe exceptionally smooth and ventional barrel. zconcfiguration whil'l'l'ha's bored out toreceive" ba'rrel tubel. Tlifibarrel jacket I is however provided with an enlarged lhe lands of the rifling formed in the barrel tube chamber 8. When barrel tube I is forced into S barrel jacket I the portion of barrel tube 1|: pros l jecting into ch'amber 8 is then spun or otherwise forced into intimate contact with the"-"walls of chamber 8. As lands 5 are ofevery-slightudepth 7. as compared to the diameter of the bore the slight indentations 6 formed by rollers I are-like wise of very shallow depth. However, the-.cross a: 3 section between the indentations 6 and the topof lands 5 is still of the same cross section as of barrel tube l and therefore-is of s'ufiic'i'ent' strength" I to withstand-any gas --pressure develol 'ed within the'bairel tube l': Additional support is provided-' by barreljacket -1. Barrel-jacket 'I also "provid'es*- themeeessaryweight "to the' barrel assembly so necessary for the reduction'of recoil and ac ,scription that the barrel tube I may be made of practically any material which can be deformed by rollers in the manner above described regardless of the toughness of machinability of such material. It should also be appreciated that provided the tubing originally had a highly polished interior bore surface the lands formed by this highiypolisl'ied 'at'the eompietiomor forming.

in this manner are quickly and readily produced. Furtherrsuch lands produced in this manner are quite inexpensively formed.

I claiin z Theimethodbf iorming a firearm-barrel con- "sisting of, placing a relatively thin metallic barrel tub'e ona mandrel which is provided with ex- I terior substantiallyohelical grooves which correspondinconfiguration to the lands desired in the firearm barrel, and then helically drawing said tube 'a ndmandrel between-a plurality 1 of rollers each" bf wh-i'li -is arranged to overlie one of -"said grooves =whereby' rolling pressures are applied to said tube along helical paths wl ich directly -overlie said g rooves 'causing metal-of saidtube to flowintosaid-greovesik l JOHN C. GARAND;