Quick-change barrel

Jan. 20, 1953

C. E. SIMPSON

QUICK CHANGE BARREL

Filed April 4, 1950

2,625,766

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Patented Jan. 20, 1953

2,625,766

UNITED STATES PATENT OFFICE

2,625,766

QUICK-CHANGE BARREL

Clarence E. Simpson, Wilbraham, Mass., assignor to the United States of America as represented by the Secretary of War

Application April 4,1950, Serial No. 153,954

Claims. (Cl. 42—75) (Granted under Title 35, U. S. Code (1952), sec. 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 firearm barrels and more particularly to improved means for effecting rapid replacement of barrels in automatic ίΪΓ6ΗΓΙ118

A serious drawback in the operation of fully automatic firearms is the tendency of the barrel to overheat during long continuous bursts of fire and thereby detract from its maximum endurance life and accuracy. Such drawback is customarily overcome by replacing the overheated barrel with a cold, unused one whenever the opportunity presents itself in order to maintain the operational efficiency of the firearm. Consequently, various devices have been provided for the purpose of avoiding any direct contact with the hot metal of the barrel during removal thereof from the firearm. However, these prior art devices have almost invariably required the use of additional parts such as handles or other protective coverings which, of course, tend to increase the overall weight of the firearm as well as complicate the barrel disassembly procedure.

It is therefore an object of the present invention to provide in an automatic firearm simple and reliable means for rigidly securing a quick change barrel therein.

It is a particular object of this invention to provide in an automatic firearm a barrel adapted for rapid disassembly and replacement without the use of tools or the necessity for manual handling of the barrel itself.

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 drawings in which:

Fig. 1 is a fragmentary longitudinal sectional view showing the barrel of this invention locked to the firearm and showing in dotted outline the path of movement of the rear end of the barrel upon disassembly from the firearm;

Fig. 2 is a fragmentary sectional view showing the details of the front barrel bearing and showing in dotted outline the path of movement of the front end of the barrel upon disassembly from the firearm;

Fig. 3 is a transverse cross-sectional view taken along the line 3—3 of Fig. 1;

Fig. 4 is a sectional view similar to Fig. 2 but showing the details of the front barrel bearing used in a gas operated firearm; and

Fig. 5 is a fragmentary view of Fig. 1 but showing the additional construction required when the quick change barrel is used with a gas operated firearm.

There is shown in Fig. 1 a firearm receiver 5 arranged to suitably house a reciprocating bolt 6 having a firing pin 7. Fixedly secured within receiver 5 by suitable means (not shown) is a 5 barrel extension 8, here shown as cylindrical in form but not necessarily limited to such configuration. Extension 8 is provided with a longitudinal bore 9 therethrough adapted to slidably receive the front end portion of bolt 6. A sub10 stantially rectangular cutaway portion 10 is provided at the front end of barrel extension 8 and extends upwardly from the bottom thereof to form a semi-circular arch portion concentric with bore 9. A semi-circular locking rib 12 con15 centric with arch portion projects downwardly therefrom for a purpose to be disclosed. At the junction of arch portion and the remainder of barrel extension 8 there is also provided a semicircular clearance recess 14 having its vertical 20 axis arranged to form a small angle relative to the vertical axis of extension 8. As a result, a portion of the vertical wall surface 13 formed by rectangular cutaway portion 10 slopes rearwardly and upwardly as shown at 16 from a point 25 slightly below the horizontal centerline of barrel extension bore 9.

A barrel II is of a conventional design but is provided with an annular groove i5 adjacent the breech end thereof and of sufficient width and 30 depth to matingly engage with rib 12 when completely assembled to extension 8 as best illustrated in Fig. 1. Moreover, the longitudinal distance between the rear surface of rib 12 and the vertical portion 13 of the wall surface formed 35 in barrel extension 8 by cutaway portion 10 is equal to the longitudinal distance between the rear end of barrel 11 and the vertical rear wall formed by annular groove 15. Thus, when barrel 11 is fully assembled to barrel extension 8, 40 the rear surface of rib 12 and vertical wall surface 13 serve to rigidly hold barrel 11 against longitudinal movement relative to extension 8. At the same time, inclined wall portion 16 introduces a limited clearance space between barrel 11 and extension 8 for permitting a swinging ^4δ downward movement of the breech end of barrel i t for unlocking from extension 8 as will be hereinafter explained. Such clearance space, however, does not detract from the proper closure of the breech in the battery position of the gun. ⁵⁰ A spring-biased pin 17 extends transversely through receiver 5 and is arranged to releasably support barrel 11 in its locked position. Barrel 11 is thus securely locked to extension 8 against 55 any tendency for longitudinal shifting movement during the discharge of a cartridge therefrom. Yet, as will be hereinafter shown, barrel I ί is free to fall of its own weight out of extension 8 when the support of pin 17 is withdrawn.

Tn the particular firearm here disclosed, re2,628,766 ceiver 5 extends forwardly to form a barrel jacket 18. As best indicated at 19 and 20 in Figs. 1 and 3, jacket 18 is open at the top and bottom thereof along substantially its entire length. Opening 20 thus provides access for the assembly and 5 disassembly of barrel II. The front end of jacket 18 is provided with a fixed annular front barrel bearing 21 having an axial opening 22 therethrough for slidably receiving the muzzle end of barrel II. An upper peripheral wall surface 23 10 of opening 22 is tapered forwardly and upwardly as shown at 24 in Figs 2 and 4 for a distance slightly greater than half the width of bearing 21 so as to form a larger elliptical circumference at the forward end of opening 22 than the di- 15 ameter thereof. The lower peripheral wall surface 25 of opening 22 is similarly tapered as shown at 26 but in a direction opposite that of taper 24. Hence, barrel 11 can be tilted an appreciable amount from the horizontal in order ²⁰to permit slidable rearward movement of the muzzle end thereof through opening 22 while the breech end is out of its horizontal locked position. Yet when barrel 11 is locked to extension 8 as previously explained, the horizontal periph- ²⁵eral wall portions 23 and 25 of opening 22 are of sufficient length to adequately support the weight of barrel 11.

In view of the foregoing, it can readily be seen that it is an extremely simple matter to re- ³⁰place a barrel in the firearm whenever so desired. To remove barrel 11 from the firearm, it is merely necessary to retract pin 17 out of supporting engagement with barrel 11 whereupon the breech end thereof will fall out of ³⁵extension cutaway portion 10 simply through its own weight. Due to the clearance between the inclined wall portion 16 of extension 8 and the rear end of barrel 11, the breech portion thereof is free to break its rigid locked connection with ⁴⁰ extension 8 and fulcrum about the peripheral edge formed by the junction of tapered wall surface 2fi and horizontal portion 25 of opening 22. Thus barrel 11 will swing downwardly through open portion 20 of barrel jacket 18 as indicated by the dotted outline shown in Fig. 1 until the inclination of the rear end is sufficient to cause the muzzle end to slide rearwardly out of front barrel bearing 21. If this swinging movement of barrel 11 is halted by the ground, it is merely necessary to thrust the entire weapon sufficiently forwardly to completely disengage the muzzle end of barrel 11 from bearing opening 22. Then a new or different barrel can be assembled to the firearm merely by inserting the muzzle end into front barrel bearing 21 and moving the breech end upwardly into locking engagement with barrel extension 8 while the retaining pin 17 is held retracted. Release of such pin will automatically complete locking of barrel 11 in the firearm.

While the firearm disclosed in Fig. 1 is of the recoil type, the barrel locking means of this invention is equally applicable to a gas operated firearm. As illustrated in Fig. 4, a conventional gas cylinder 27 is suitably provided adjacent the front end of barrel jacket 18. A gas port 28 in barrel 11 is aligned with a gas port 29 in gas cylinder 27 through a passage 30 formed through the upper portion of be’aring 21. In order to assure correct alignment of gas port 28 with passage 30 when barrel 11 is in its locked position, there is provided in barrel extension 8 a fixed stud 31 arranged to extend into a suitable hole 32 in the breech end of barrel II, Therefore, barrel 11 must be positioned so that stud 31 will engage in hole 32 thereby properly qualifying gas port 28 with gas passage 30. Otherwise, assembly and disassembly is identical to the procedure previously explained.

Accordingly, the construction herein presented assures extremely rapid and simple replacement of barrels in automatic firearms without requiring any manual contact with the hot barrel during the step of disassembly.