US3446111A

US3446111A - Recoilless open chamber gun

Info

Publication number: US3446111A
Application number: US664979A
Authority: US
Inventors: David Dardick
Original assignee: TRW Inc
Current assignee: Northrop Grumman Space and Mission Systems Corp; Tround International Inc
Priority date: 1967-09-01
Filing date: 1967-09-01
Publication date: 1969-05-27
Anticipated expiration: 1986-05-27
Also published as: FR1603953A; SE352947B; ES357762A1; BE720218A; IL30609A0; GB1243845A; CH491352A

Description

May 27, 1969 D. DARDICK RECOILLESS OPEN CHAMBER GUN Sheet 01'3 Filed Sept. 1, 1967 INVEN'I 0R Dmf/o lineal CK y 27, 1969 D. DARDICK 3,446,111

RECOILLESS OPEN CHAMBER GUN Filed Sept. 1. 1967 Sheet 3 of 3 I I02 H5 Ha. (I03 8 I N VEN TOR v DOV/D .DAQD/CK kam w May 27, 1969 D. DARDICK 3,446,111

RECOILLESS OPEN CHAMBER GUN Filed Sept. 1, 1967 Sheet 3 of 3 D4 we .DAPO/CK INVENTOR.

United States Patent O 3,446,111 RECOILLESS OPEN CHAMBER GUN David Dardick, Palos Verdes Peninsula, Calif., assignor to TRW Inc., Redondo Beach, Calif., a corporation of Ohio Filed Sept. 1, 1967, Ser. No. 664,979 Int. Cl. F41f 3/02, 15/00 US. Cl. 891.7 7 Claims ABSTRACT OF THE DISCLOSURE A recoilless open chamber gun having rearwardly opening venturi means through which a portion of the high pressure propellant gas generated during firing exits at high velocity to produce on the gun a counter-recoil force equal and opposite to the recoil force exerted on the gun during firing.

REFERENCE TO COPENDING APPLICATIONS Reference is made herein to copending applications Ser. No. 671,910, filed Sept. 1, 1967, and entitled, Sealed Open Chamber Breech Mechanism and Caseless Ammunition Therefor, Ser. No. 665,136, filed Sept. 1, 1967, and entitled Semicombustible Ammunition for Open Chamber Breech Mechanism, and Ser. No. 665,160, filed Sept. 1, 1967, and entitled, Ammunition Improvements to Permit Firing of a Conventional Closed Chamber Cartridge in an Open Chamber Breech Mechanism.

BACKGROUND OF THE INVENTION Field of the invention Prior art It is well known in the art that all weapons, when fired, experience a rearward recoil force which is equal and opposite to the forward propulsion force exerted on the projectile for propelling the latter forwardly through the gun bore. In small caliber weapons, such as rifles and pistols, the magnitude of this recoil force is relatively small and can be sustained by the person firing the weapon. In larger caliber weapons, on the other hand, the recoil force is relatively large and must be absorbed or neutralized in some way. For example, in some large caliber weapons, i.e., recoiling weapons, the breech mechanism is supported by a cradle for recoil and counter-recoil movement, and the kinetic energy of the recoil breech mechanism following firing is absorbed by counter-recoil means which arrest the breech mechanism with a cushioning action and then return the mechanism to battery position. In other larger caliber weapons, i.e., recoilless weapons, a portion of the high pressure propellant gas generated during the firing is directed through rearwardly opening venturi means in the breech end of the weapon to produce on the weapon a counter-recoil force substantially equal in magnitude and opposite in direction to the recoil force on the weapon. The present invention is concerned with this latter technique of counteracting recoil force.

ICC

Conventional recoilless weapons, while effective to neutralize the recoil force produced during firing, are deficient in that they are incapable of automatic high rate firing. This deficiency results from the relatively long length of recoilless ammunition necessary to contain the additional propellant required to develop the counter-recoil thrust and to the four step firing cycle employed in conventional automatic weapons. Thus, the firing cycle of such weapons involves initial lateral infeed movement of each round into the breech, axial insertion or ramming of the round into the firing chamber, axial removal or extraction of the spent cartridge case from the chamber after firing, and final lateral ejection of the cartridge case. This necessity of axially ramming each round into and axially extracting the spent cartridge case of each round from the firing chamber, coupled with the relatively long overall length of the conventional recoilless ammunition round, precludes high rate automatic firing of conventional recoilless weapons.

The above-noted disadvantages which attend conventional closed chamber guns and their four step firing cycle are avoided in guns having a so-called open chamber breech mechanism. Guns of this type, for example, are disclosed in Patents Nos. 2,983,223; 3,041,938; 2,831,140; 2,847,784; 3,046,890. Generally speaking, such an open chamber gun is characterized by an open chamber breech mechanism including a breech frame having a chamber containing a rotary carrier or cylinder with one or more firing chambers which open laterally through the circumference and longtiudinally through the forward end of the cylinder. The cylinder is supported on the breech frame for rotation or oscillation to sequentially locate each firing chamber in an ammunition infeed position, a firing position, and, when firing cased ammunition, a cartridge case ejection position. When in infeed position, the open side of the firing chamber registers with a lateral ammunition infeed opening in the breech frame to permit lateral infeed movement of an ammunition round into the chamber. When in firing position, the firing chamber is closed by the breech frame and opens forwardly to the gun bore to condition the breech mechanism for firing the round in the chamber. When in ejection position, the open side of the firing chamber registers with a lateral ejection opening in the breech frame to permit lateral ejection of the spent cartridge case from the chamber after firing. A primary advantage of an open chamber breech mechanism, then, is its effectively two-step firing cycle involving initial lateral infeed movement of each ammunition round to firing position and final lateral ejection of each spent cartridge case from firing position. As a consequence, the total travel of each ammunition round through an open chamber breech mechanism from infeed to ejection is independent of and but a fraction of the overall length of the round and is substantially less than the total ammunition travel through a conventional closed chamber breech mechanism. In one type of open chamber gun, referred to herein as a fixed barrel gun, each gun barrel is secured to and remains stationary with the breech frame, and each firing chamber is stationarily aligned with the barrel during firing. In another type of open chamber gun, referred to herein as a rotary barrel gun, each barrel is secured to and rotates continuously with the cylinder, even during firing, to achieve a high firing rate.

It is now evident, therefore, that the open chamber concept is uniquely adapted to an automatic, high rate recoilless firing action. The open chamber breech mechanisms, disclosed in the aforementioned prior patents, however, are incapable of such recoilless firing action owing to the fact that they lack means for utilizing a portion of the propellant gas generated during firing to produce a counter-recoil thrust on the breech mechanism.

SUMMARY OF THE INVENTION This invention provides an open chamber gun which is designed to provide a recoilless firing action. To this end, the open chamber gun of the invention comprises a basic open chamber breech structure essentially identical to those disclosed in the earlier mentioned patents. According to the present invention, the breech frame is provided with rearwardly opening venturi means which communicate with the firing chamber when the latter occupies its firing position. When an ammunition round is fired in the chamber, a portion of the high pressure propellant gas issues at high velocity through the venturi means to produce on the gun a counter-recoil thrust substantially equal and opposite to the recoil force exerted on the gun. In one disclosed embodiment of the invention, for example, the firing chamber and venturi means communicate via propellant gas plenums which extend longitudinally through the breech frame firing strap and cylinder and communicate laterally to the firing chamber through ports in the inner wall of the firing strap and the side walls of the firing chamber. In another disclosed embodiment of the invention, the venturi means communicate with the firing chamber through passages in the rear Wall of the chamber.

It is significant to recall here that the present recoilless open chamber gun may fire cased, semi-combustible, and caseless ammunition. In this regard, attention is directed to the earlier mentioned copending applications and patents which disclose these various types of ammunition. Also, the gun may have either a fixed barrel or a rotary barrel construction.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings:

FIG. 1 is a side elevation, partly in section, of a fixed barrel recoilless open chamber gun according to the invention;

FIG. 2 is an enlarged section taken on line 22 in FIG. 1;

FIG. 3 is a fragmentary section taken on line 3-3 in FIG. 2;

FIG. 4 is a rear end view of the gun looking in the direction of the arrows on line 44 in FIG. 1;

FIG. 5 is an enlarged section taken on line 55 in FIG. 2;

FIG. 6 is a perspective view, partly broken away, of an open chamber ammunition round which may be fired in the recoilless open chamber gun of the invention;

FIG. 7 is a longitudinal section through a modified open chamber ammunition round which may he fired in the present open chamber gun, the ammunition round in this case containing a conventional recoilless cartridge;

FIG. 8 is an enlarged fragmentary longitudinal section through a modified recoilless open chamber gun according to the invention;

FIG. 9 is a perspective view of a recoilless rotary barrel open chamber gun according to the invention; and

FIG. 10 is a longitudinal section through the gun of FIG. 9.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In general terms, the invention provides a recoilless open chamber gun, represented in the drawings by the gun 10, having an open chamber breech mechanism 11 including a breech frame 12 containing a chamber 14. Rotatably supported on the frame within the chamber, for rotation on an axis 16, is an open chamber carrier or cylinder 18. Chamber 14 opens laterally through opposite sides of the frame to form ammunition infeed and cartridge case ejection openings for the carrier, as explained below.

Extending forwardly from the front end of the breech 12, in spaced parallel relation to the cylinder axis 16, is a barrel 20 containing a bore 22. The rear end of the bore opens to the chamber 14, in confronting relation to the front end of the breech cylinder 18. Cylinder 18 contains a longitudinal firing chamber 24 which opens laterally through the circumference and longitudinally through the front end of the cylinder. Extending coaxially from the rear end of the cylinder, and rotatably through the rear end of the breech frame 12, is a shaft 26 by which the cylinder may be rotated or oscillated to sequentially locate its firing chamber 24 in ammunition infeed, firing and cartridge case ejection positions. When the firing chamber is in infeed position, the open side of the chamber registers with the ammunition infeed opening in the breech frame 12 for receiving through the opening an ammunition round 30 to be fired. In the simplified breech mechanism illustrated, this infeed opening is defined by one open side of the chamber 14. When in firing position, the open side of the firing chamber is closed by the breech frame firing strap 32, and the firing chamber is coaxially aligned with and opens forwardly to the gun bore 22. When in ejection position, the open side of the firing chamber registers with the cartridge case ejection opening in the breech frame which in this instance, like the infeed opening, is defined by one open side of the chamber 14. Breech mechanism 11 is equipped with firing means 36, such as a conventional firing pin mechanism, for firing the round 30 in the firing chamber 24 when the latter occupies its firing position.

As thus far described, the open chamber gun is conventional. According to the present invention, the gun is equipped with rearwardly opening venturi means 38 and with passage means 40 for communicating the venturi means to the firing chamber 24 when the latter occupies its firing position. During firing of an ammunition round 30 in the gun, a portion of the high pressure propellant gas generated by the burning propellant charge in the round issues at high velocity through the venturi means 38 to produce a forward, counter-recoil thrust on the gun. The counter-recoil means, consisting of the venturi means 38 and passage means 40, are so constructed and arranged that the magnitude of this counter-recoil thrust is substantially equal to the rearward, recoil force exerted on the gun during firing. Accordingly, during firing the present open chamber gun is subjected to substantially equal and opposite recoil and counter-recoil forces, whereby the gun exhibits a recoilless firing action.

In the particular, recoilless open chamber gun 10 of the invention which has been selected for illustration in FIGS. 1-5 the counter-recoil venturi means 38 comprise three separate venturis 42, 44, and 46 which are generally circularly curved in cross-section about axes which parallel the axis of the cylinder 18. The passage means 40 comprise three separate gas passages or plenums 48, 50, and 52 which communicate the venturis 42, 44, and 46, respectively, to the firing chamber 24. Plenum 48 extends longitudinally through the breech frame firing strap 32 and opens laterally to the chamber 14 through a number of longitudinal spaced ports 54 in the inner wall of the strap. The rear end of this plenum opens to the breech venturi 42. Plenums 50 and 52 extend longitudinally through the breech cylinder 18, at opposite sides of the firing chamber 24, and open laterally to the firing chamber through a number of ports 56 in the side walls of the chamber. When the firing chamber occupies its firing position, the rear ends of the cylinder plenums 50, 52 register with and open to the breech venturis 44, 46.

The operation of the illustrated recoilless open chamber gun 10 of the invention is believed to be obvious from the preceding description. Thus, when an ammunition round 30 is to be fired in the gun, the breech carrier or cylinder 18 is rotated to locate its firing chamber 24 in infeed position and the round is introduced laterally into the chamber. The cylinder is then rotated to locate the firing chamber in firing position, and the round is fired by actuation of the breech firing means 36. A major portion of the propellant gas generated within the firing chamber during such firing propels the projectile of the round forwardly through the gun bore 22. The remaining propellant gas flows from the firing chamber through the plenum ports 54, 56 and the propellant gas plenums 48, 50, 52 to the breech venturis 42, 44, 46 and then exits at high velocity through these venturis to produce on the gun a counter-recoil thrust substantially equal and opposite to the recoil force exerted on the gun as a consequence of forward propulsion of the projectile from the gun. In this regard, it will be understood that the venturis 42, 44, 46, plenums 48, 40, 52 and ports 54, 56 are so sized that the counter-recoil thrust produced by the propellant gas issuing through the venturis substantially equals the recoil force on the gun during firing.

At this point, it is significant to recall that a variety of ammunition rounds may be fired in the present recoilless open chamber gun. The ammunition round 30, for example, is also called semi-co bustible open chamber ammunition round of the type disclosed in the aforementioned copending application Ser. No. 665,136, entitled Semi-Combustible Ammunition for Open Chamber Breech Mechanism. This round comprises a yieldable, noncombustible plastic cartridge case 58 (FIG. 6) containing 21 propellant charge 60 and a projectile 62.

As is characteristic of open chamber guns and ammunition of the kind under discussion, the cylinder firing chamber 24 and the ammunition cartridge case 58 have complementary, generally triangular round shapes in cross section. This particular firing chamber and ammunition shape has several advantages which are fully explained in the aforementioned prior art patents. Accordingly, these advantages will not be repeated here. Suffice it to say that the two side walls of the firing chamber 24 and the three sides of the ammunition cartridge case 58 are cylindrically rounded to the same radius of curvature as the circumference of the breech cylinder 18. Accordingly, when the ammunition round 30 is positioned in the firing chamber, the side of the round which is exposed in the open side of the firing chamber is substantially flush with the cylinder circumference. The inner Wall of the breech frame firing strap 32 is cylindrically curved to the same radius and slidably engages the circumference of the breech cylinder. Accordingly, when the round 30 is rotated to firing position, the exposed wall of the round seats flush against the inner Wall of the firing strap. In the particular semi-combustible ammunition under consideration, the three sides of the cartridge case 58 are formed with openings 64 which uncover or expose the plenum ports 54, 56 in the breech mechanism 11 when the firing chamber occupies its firing position. It is now evident, that when the round 30 is fired in the gun, a portion of the propellant gas is permitted to flow from the firing chamber, through the ports 54, 56, into the breech plenums 48, 50, 52. and then through these plenums to the breech venturis 42, 44, 46 in the manner explained above. As discussed in the last-mentioned copending application, the propellant gas generated within the cartridge case 58 during firing expands the case the elfect sealing of the breech interfaces against propellant gas leakage.

Among the other types of ammunition which may be fired in the present recoilless open chamber gun is the caseless ammunition disclosed in the aforementioned copending application, Ser. No. 671,910, entitled Sealed Open Chamber Breech Mechanism and Caseless Ammunition Therefor. In this case, it will be understod that the breech mechanism will be equipped with suitable obturator means, such as the obturator means disclosed in the application, for sealing the breech interfaces against propellant gas leakage during firing. Moreover, since the ammunition is caseless, the need for rotating the firing chamber 24 to ejection position after firing is eliminated. FIG. 7 illustrates a round 65 of yet another type of open chamber ammunition which may be fired in the present recoilless open chamber gun. In this case, the ammunition is like that disclosed in the aforementioned copending application Ser. No. 665,160, entitled, Ammunition Improvements To Permit Firing of a Conventional Closed Chamber Cartridge in an Open Chamber Breech Mechanism, and comprises a standard recoilless ammunition cartridge 66 contained within a plastic adapted sleeve or jacket 68.

This jacket has side openings 70 which expose the propellant gas ports 72 in the cartridge case 74 of the recoilless cartridge 66. The ammunition jacket 68 has the same external, generally triangular round shape in cross section as the round 30 and is designed to permit firing of the standard recoilless cartridge 66 in an open chamber gun.

Reference is now made to FIG. 8 illustrating a modified recoilless, open chamber gun according to the invention and a round 102 of modified recoilless ammunition to be fired in the gun. Gun 100 is basically identical to the gun 10 described earlier and, accordingly, need not be explained in detail. Sufiice it to say that the guns differ only in their respective counter-recoil thrust producing means. Thus, the modified gun 100 is provided with rearwardly opening venturis 104 in the rear end of the breech frame 106 which communicate forwardly to the breech cylinder firing chamber 108,.when the latter occupies its illustrated firing position. The recoilless ammunition round 102 has a plastic cartridge case 112 of the same generally triangular round shape in cross section as the earlier described rounds. This cartridge case contains a propellant charge 114 and a projectile 116. In contrast to the earlier described ammunition rounds, however, the sides of the cartridge case 112 are completely closed and the rear end wall of the case is provided with ports containing blowout plugs 118 which register with the venturis 104 when the ammunition round 102 is located in firing position. When the ammunition round is fired, propellant gas pressure blows the plugs 118 rearwardly through the venturis 104 to permit a portion of the propellant gas to issue at high velocity through the venturis and thereby produce a counter-recoil thrust on the gun. As in the earlier embodiment of the invention, the venturis 104 are so sized that this counter-recoil thrust is substantially equal to the recoil force exerted on the gun during firing.

All of the open chamber guns described thus far have fixed barrels which are secured to and remain stationary with the breech frame. The aforementioned Patent No. 3,041,939 discloses another type of open chamber gun referred to herein as a rotary barrel open chamber gun. In this type of gun, the barrel or barrels are fixed to and rotate with the breech carrier or cylinder. The cylinder and barrels undergo continuous rotation, even during firing, whereby the gun is characterized by an extremely high firing rate. FIGS. 9 and 10 illustrate a recoilless rotary barrel open chamber gun 200 according to the invention. Gun 200 has a breech frame 202 including a central portion 204 and integral coaxial flange-like bearing rings 206, 208 at the front and rear ends of the central frame portion. Within the breech frame, on the common axis of the bearing rings 206, 208, is a cylinder receiving chamber 210. Chamber 210 opens longitudinally through the front and rear ends of the breech frame and laterally through opposite sides of the central frame portion 204. As in the earlier embodiments of the invention, the side openings in the breech frame 202 provide lateral ammunition infeed and ejection openings to the cylinder receiving chamber.

Rotatable within and on the axis of the chamber 210 is a carrier or cylinder 212. The front and rear ends of this cylinder are exposed through the central openings in the bearing rings 206, 208. Breech cylinder 210 is rotatably supported on the breech frame 202 by a pair of bearing units 214 which surround the ends of the cylinder in the planes of the bearing rings, respectively. Breech cylinder 212 contains a number of uniformly spaced longitudinal firing chambers 216. Each firing chamber opens laterally through the circumference of the cylinder in the region between the breech frame bearing rings 206, 208. Each firing chamber is thus bounded at its ends by front and rear end walls 218, 220, respectively.

Associated with each firing chamber 216 is a gun barrel 222. Each barrel is secured to the front end wall 218 of its respective firing chamber, as by being threaded in the wall, in such a way that the bore 224 contained in the barrel is coaxially aligned with and opens rearwardly to the firing chamber. It is now evident, therefore, that the gun barrels 222 are rotatable with the breech cylinder 212.

At the rear end of the breech frame 202 is a motor 226 for driving the breech cylinder 212 continuously in unidirectional rotation. During this rotation, the cylinder firing chambers 216 rotate through ammunition infeed, firing, and ejection positions. When in infeed position, the open side of each firing chamber registers with the breech frame ammunition infeed opening to permit lateral infeed movement of an ammunition round 228 to be fired into the chamber from ammunition infeed means (not shown). In firing position, the open side of each firing chamber is closed by the breech frame firing strap 230 to permit firing of the ammunition round in the chamber. It will be understood that a rotary barrel gun may have more than one firing station and a corresponding number of firing straps. For convenience, it is assumed that the illustrated gun has a single firing station. When in ejection position, the open side of each firing chamber registers with the breech frame ejection opening to permit lateral ejection of the spent cartridge case of a fired round or an unfired round.

The opening chamber gun 200 is equipped with firing means 232 for firing each ammunition round 228 in firing position. The illustrated firing means are assumed to be electrically actuated firing means which are energized in firing position by engagement of contacts 233a on the cylinder 212 for each firing means with energizing contacts 23% on the firing strap 230.

It will be recognized that the open chamber gun 200 is generally conventional as it is thus far described. During operation of the gun, the breech cylinder 212 is driven continuously in rotation to rotate its firing chambers 216 in succession through infeed, firing, and ejection positions. Each firing chamber receives an ammunition round 228- in firing position, the round is fired in firing position, and the spent cartridge case of the round is ejected in ejection position. The gun barrels 222 rotate with the breech cylinder, as already noted, whereby the cylinder can continue to rotate during firing to provide the gun with a high firing rate capability.

According to the present invention, the gun 200 is improved by providing the same with a counter-recoil action similar to that described above in connection with the gun of FIG. 8. To this end, the ammunition rounds 228 which are fixed in the gun 200 are identical, except for the electrical primer in the latter rounds, to the ammunition rounds 102 which are fixed in the gun of FIG. 8. Also, the rear end wall 220 of each firing chamber 216 in the gun 200 is provided with rearwardly opening venturis 234- which register with the blowout plugs 236 of an ammunition round 228 contained in the respective firing chamber. Accordingly, during firing of each round in the gun 200, a portion of the high pressure propellant gas generated within the round exits through the venturis 234 of its firing chamber to produce a counter-recoil thrust on the gun, all in essentially the same manner as described earlier in connection with FIG. 8. The rotary barrel open chamber gun 200, therefore, has a recoilless firing action. The cylinder drive motor 226 is attached to the rear end of the breech frame 202 in such a way that the motor uncovers the venturis of each firing chamber 216 in firing position, as shown.

At this point, it will be evident to those versed in the art that while the invention has been disclosed in connection with open chamber guns having rotary open chamber carriers or cylinders, the recoilless firing features of the invention may be embodied, as well, in an open chamber gun having a so-called breech mechanism.

In this type of open chamber breech mechanism, the firing chamber or chambers are contained in separate open chamber carriers supported by a conveyor of some type which is driven endwise through the breech frame to locate each firing chamber in infeed, firing, and ejection positions.

What is claimed as new in support of Letters Patent is: 1. A recoilless open chamber gun comprising: a breech frame containing a chamber; a carrier supported on said frame within said chamber for rotation on an axis; said frame having an ammunition infeed opening to said chamber between the ends of said carrier, and rearwardly opening venturi means; said carrier containing a longitudinal firing chamber opening laterally through the circumference of said carrier and longitudinally through the front end of said carrier; a barrel extending forwardly of said frame in spaced parallel relation to said carrier axis; said carrier being rotatable in said breech chamber to locate said firing chamber in an ammunition infeed position, wherein the open side of said firing chamber registers with said infeed opening to receive a round of ammunition through said opening, and a firing position, wherein the open side of said firing chamber is closed by said breech frame and said firing chamber opens forwardly to the bore on said barrel to condition said gun for firing said round to generate a high pressure propellant gas in said firing chamber; there being passage means communicating said firing chamber and venturi means in firing psition, whereby a portion of said propellant gas issues at high velocity through said venturi means during firing of said round to produce on said gun a counter-recoil thrust opposing the recoil force exerted on said gun during firing; and said passage means comprising a plenum extending longitudinally through said carrier along one side of said firing chamber and opening laterally to said firing chamber through a sidewall of said firing cham ber, and said plenum communicating with said venturi means when said firing chamber occupies said firing position. 2. A recoilless open chamber gun comprising: a breech frame containing a chamber; a carrier supported on said frame within said chamber for rotation on an axis; said frame having an ammunition infeed opening to said chamber between the ends of said carrier, and rearwardly opening venturi means; said carrier containing a longitudinal firing chamber opening laterally through the circumference of said carrier and longitudinally through the front end of said carrier; a barrel extending forwardly of said frame in spaced parallel relation to said carrier axis; said carrier being rotatable in said breech chamber to locate said firing chamber in an ammunition infeed position, wherein the open side of said firing chamber registers with said infeed opening to receive a round of ammunition through said opening, and a firing position, wherein the open side of said firing chamber is closed by said breech frame and said firing chamber opens forwardly to the bore in said barrel to condition said gun for firing said round to generate a high pressure propellant gas in said firing chamber; there being passage means communicating said firing chamber and venturi means in firing position, whereby a portion of said propellant gas issues at a high velocity through said venturi means during firing of said round to produce on said gun a counter-recoil thrust opposing the recoil force exerted on said gun during firing; and

said passage means comprising a pair of plenums extending longitudinally through said carrier along opposite sides of said firing chamber and opening laterally to said firing chamber through the sidewalls of said firing chamber, and said plenum communicating with said venturi means when said firing chamber occupies said firing position.

3. A recoilless open chamber gun comprising:

a breech frame containing a chamber;

a carrier supported on said frame within said chamber for rotation on an axis;

said frame having an ammunition infeed opening to said chamber between the ends of said carrier, and rearwardly opening venturi means;

said carrier containing a longitudinal firing chamber opening laterally through the circumference of said carrier and longitudinally through the front end of said carrier;

a barrel extending forwardly of said frame in spaced parallel relation to said carrier axis;

said carrier being rotatable in said breech chamber to locate said firing chamber in an ammunition infeed position, wherein the open side of said firing chamber registers with said infeed opening to receive a round of ammunition through said opening, and a firing position, wherein the open side of said firing chamber is closed by said breech frame and said firing chamber opens forwardly to the bore in said barrel to condition said gun for firing said round to generate a high pressure propellant gas in said firing chamber;

there being passage means communicating said firing chamber and venturi means in firing position, whereby a portion of said propellant gas issues at high velocity through said venturi means during firing of said round to produce on said gun a counter-recoil thrust opposing the recoil force exerted on said gun during firing;

said breech frame including a firing strap which closes the open side of said firing chamber when said firing chamber occupies said firing position; and

said passage means comprising a plenum extending longitudinally through said firing strap and opening laterally to said breech chamber through the inner wall of said firing strap for communication of said plenum with said firing chamber when said firing chamber occupies said firing position, and said plenum communicating with said venturi means.

4. A recoilless open chamber gun comprising:

a breech frame member containing a chamber,

a carrier member supported on said frame member within said chamber for rotation on an axis,

said frame member having an ammunition infeed opening to said chamber between the ends of said carrier member and rearwardly opening venturi means,

said carrier member containing a longitudinal firing chamber opening laterally through the circumference of said carrier member and longitudinally through the front end of said carrier member,

a barrel extending forwardly of said frame member in spaced parallel relation to said carrier axis,

said carrier member being rotatable in said breech chamber to locate said firing chamber in an ammunition infeed position, wherein the open side of said firing chamber registers with said ammunition infeed opening to receive a round of ammunition through said opening, and a firing position, wherein the open side of said firing chamber is closed by said breech frame and said firing chamber opens forwardly to the bore in said barrel to condition said gun for firing said round to generate a high pressure propellent gas in said firing chamber, and

there being passage means communicating said venturi means and firing chamber in firing position, whereby a portion of said propellant gas issues at high velocity through venturi means during firing to produce a counter-recoil thrust on said gun opposing the recoil force exerted on said gun during firing, said passage means including a plenum extending longitudinally through each of said members and opening laterally to said firing chamber when said firing chamber occupies its firing position.

5. A recoilless open chamber gun comprising: a breech frame containing a chamber, a cylinder supported on said frame within said chamber for rotation on an axis,

a barrel secured to and extending forwardly from the front end of said frame in spaced parallel relation to said axis and containing a bore opening rearwardly to said chamber in confronting relation to the front of said cylinder,

said breech frame having a lateral ammunition infeed opening to said chamber between the ends of said cylinder, rearwardly opening venturi means in the rear end of said frame, and a firing strap,

said cylinder containing a firing chamber opening laterally through the circumference of said cylinder and longitudinally through the front end of said cylinder,

said cylinder being rotatable in said frame to locate said firing strap having a plenum extending longitudinally through said strap and communicating with said venturi means, and ports extending laterally from said plenum through the inner wall of said firing strap for communication with said firing chamber when said firing chamber occupies said firing position, and

said cylinder containing a pair of plenums extending longitudinally through said cylinder at opposite sides of said firing chamber and communicating with said venturi means in firing position, and ports extending laterally from said cylinder plenums through the sidewalls of said firing chamber, whereby a portion of said propellant gas issues at high velocity through said venturi means to produce a counterrecoil thrust on said gun opposing the recoil force exerted on said gun during firing.

6. A recoilless open chamber gun for firing open chamber ammunition rounds each having a generally triangular round shape in transverse cross-section, comprising:

a barrel containing a bore;

an open chamber breech mechanism at the breech end of said barrel including a breech frame containing a chamber and a lateral ammunition infeed opening to said chamber, an ammunition carrier positioned within said chamber and containing a longitudinal firing chamber of generally triangular round shape in transverse cross section opening longitudinally through the front end and laterally through the circumference of said carrier, and means supporting said carrier on said frame for rotation between an ammunition infeed position wherein the open side of said firing chamber registers with said infeed opening to permit lateral infeed movement of an open chamber ammunition round into said firing chamber and a firing position wherein the open side of said firing chamber is closed by said frame and said firing chamber is coaxially aligned with and opens forwardly to said bore to condition said gun for firing an ammunition round in said firing chamher to generate a high pressure propellant gas in said firing chamber;

said breech mechanism having rearwardly opening venturi means and passage means communicating said venturi means and firing chamberrin firing position, whereby a portion of said propellant gas issues at high velocity through said venturi means during firing to produce on said gun a counter-recoil thrust opposing the recoil force exerted on said gun during firing; and

said passage means opening laterally to said firing chamber in firing position between the ends and through at least one longitudinal side of said firing chamber.

7. An open chamber gun according to claim 6, wherein:

said passage means open laterally to said firing chamber through at least two longitudinal sides of said firing chamber.

1 2 References Cited UNITED STATES PATENTS 4/1957 Bird 4239.5 X 7/1957 Atherton 89--1.803 12/1958 Dardick 42-39.5 4/1962 Musser 89--1.706

FOREIGN PATENTS 9/1949 Switzerland.

SAMUEL w. ENGLE, Primary Examiner.

US. Cl. X.R.