US3552625A

US3552625A - Explosive charge operated setting tool or gun

Info

Publication number: US3552625A
Application number: US806184A
Authority: US
Inventors: Karl-Ernst Udert
Original assignee: Hilti AG
Current assignee: Hilti AG
Priority date: 1968-11-13
Filing date: 1969-03-11
Publication date: 1971-01-05
Anticipated expiration: 1988-01-05
Also published as: DE1808703B2; DE1808703C3; DE1808703A1

Abstract

An explosive charge operated setting tool or gun for driving anchoring elements into hard receiving material such as concrete or steel comprises a housing in which is axially slidable a hollow barrel. A drive piston is slidable within the barrel and it is moved forward rapidly under the force of an explosive charge to drive an anchoring element which is positioned within a stand plate end portion of the barrel into the receiving material. The barrel has an inner end portion which terminates in an outwardly flaring cartridge chamber. The housing, together with a pistol grip extension or handle, defines a magazine channel which extends at substantially right angles to the movement and direction of the barrel. A disposable magazine preferably of a resilient material such as plastic is provided with a plurality of tubular projections defining cartridge receiving recesses. Cartridges are held in the magazine within the recesses so that the forward tips project outwardly in a direction toward the barrel and they are successively aligned with the barrel for successive firing thereof. At the rear, the cartridge magazine abuts against the cartridge chamber breech at its rear end and its opposite end which includes the tubular projection surrounding the cartridge and the base of the band provide a sealing engagement with the portion of the barrel surrounding the cartridge receiving chamber therein. The plastic band of the cartridge magazine forms a necessary wall portion of the closed cartridge chamber and it provides a sealing for the gases upon explosion of the cartridge and during the initial forward movement of the barrel and the drive piston therein.

Description

United States Patent [72] inventor Karl-Ernst Udert ABSTRACT: An explosive charge operated setting tool or gun Matschils, Liechtenstein for driving anchoring elements into hard receiving material [21 Appl. No. 806,184 such as concrete or steel comprises a housing in which is axi- [22] Filed Mar. 11, 1969 ally slidable a hollow barrel. A drive piston is slidable within [45] Patented Jan. 5, 1971 the barrel and it is moved forward rapidly under the force of [73] Assignee HiltiAktiengesellschaft an explosive charge to drive an anchoring element which is Schaan, Furstentum, Liechtenstein positioned within a stand plate end portion of the barrel into [32] Priority Nov. 13, 1968 the receiving material. The barrel has an inner end portion [33] Germany which terminates in an outwardly flaring cartridge chamber. [31] No. 1,808,703 The housing, together with a pistol grip extension or handle, defines a magazine channel which extends at substantially right angles to the movement and direction of the barrel. A EXPLOSIVE CHARGE OPERATED SETTING TOOL disposable magazine preferably of a resilient material such as on GUN plastic is provided with a plurality of tubular projections defin- 12 chimsflnl'awing Figsing cartridge receiving recesses. Cartridges are held in the 52] US. Cl 227/10 magazifie Within the recesses 80 that the forward p P j [51 1 25 1/14 outwardly in a direction toward the barrel and they are succes- [50] Field of Search 227/8, 9, silely aligned with the barrel for Successive firing thefeof- At 10 1 the rear, the cartridge magazine abuts against the cartridge chamber breech at its rear end and its opposite end which in- [56] References Cited cludes the tubular projection surrounding the cartridge and UNITED STATES PATENTS the base of the band provide a sealing engagement with the portion of the barrel surrounding the cartridge receiving 58f: chamber therein. The plastic band of the cartridge magazine 33638l7 [1968 Brad; 227 forms a necessary wall portion of the closed cartridge chamber and it provides a sealing for the gases upon explosion Primary ExaminerGranville Y. Custer, Jr. of the cartridge and during the initial forward movement of Attorney- McGlew and Toren the barrel and the drive piston therein.

Z T 31 3 2 I o '9's i7"x 7 10 8 a i I \\l lr n l AM] I LL I //a4 50 g a i a; Ga r a m a 00 L5 f I la x W n EXPLOSIVE CHARGE OPERATED SETTING TOOL OR GUN SUMMARY OF THE INVENTION This invention relates, in general, to the construction of explosive charge operated devices and, in particular, to a new and useful gun or setting tool for driving anchoring elements into hard receiving material which includes a magazine for feeding the cartridges into a cartridge chamber defined in the rear portion of a moving barrel of the device and wherein the magazine provides a seal with the barrel during the operation of the device.

In the known constructions of guns of the type with which the present invention is concerned, the cartridges are pushed out of the magazine and into a cartridgechamber by so-called ejector or pusher elements. The cartridge chamber is then closed in a conventional manner and the cartridge is ignited. Such a cartridge feed is complicated and difficulties may occur during the operation either because the cartridge jams in the magazine and is not ejected or because the ejector pusher mechanism malfunctions. .With such a mechanism, there is also the danger of premature ignition of the cartridge due to a too powerful contact with the ejector.

In accordance with the present invention, there is provided a gun which includes a disposable magazine preferably made of a material such as plastic which carries a plurality of cartridges for automatic feeding to a cartridge chamber defined in the rear end of a moving barrel of the gun. The magazine is advantageously formed as a plastic band and it preferably includes cylindrical or tubular portions on the one side which encompass only the lower portion of the cartridge in a manner such that the tip projects outwardly therefrom. Sealing of the cartridge chamber is effected between the moving barrel and the breech by a portion of the magazine material itself. Thus, the construction of the invention avoids the disadvantages of the prior art and provides a rugged and reliable construction which is less complicated since it has an automatic magazine feed. By using a disposable magazine construction, which can be produced economically of a plastic material, the ejector and the pusher mechanism for pushing the cartridge out of the magazine into the cartridge chamber can be eliminated. Another considerable advantage results from the fact that in the present guns, the ejector mechanism which is necessary to push the cartridge after ignition out of the cartridge chamber can also be eliminated. With the present construction, after the cartridge is ignited it still remains in the magazine recess and it will be moved upwardly out of alignment with the cartridge chamber during the returning movement of the barrel in a complete operation cycle.

The invention is based upon the realization that the magazine material itself may be employed to close the cartridge chamber instead of requiring a steel breech which touches the chamber directly during the ignition process. Thus, the cartridge chamber barrel need no longer be placed in direct contact with the breech but a plastic magazine may be interposed therebetween. Contrary to the opinion of experts in the field, it has been found that in a majority of practical cases, the interposition of plastic between the breech plate and the cartridge chamber can withstand considerable compressive stresses during the explosion of the cartridge. This is surprising insofar as an additional support of the plastic and such a band-shaped cartridge magazine can be effected at best in two directions transverse to the feeding direction of the magazine, but not in or opposite to the magazine feeding direction. While it has been known to fire plastic covered cartridges in bolt setting guns, the steel part of the cartridge chamber embraces the total height of the surrounding plastic so that the steel is supported in all directions, in contrast to the present construction, in which the plastic magazine surrounds only a portion of the cartridge adjacent its base and the sealing is effected between the barrel and the breech.

A polyolefin plastic preferably a polypropylene or polyethylene is particularly suitable as a plastic material for the magazine.

In a preferred embodiment of the gun construction, according to the invention, where the opening of the passage of the powder gases into the barrel is smaller in its cross section than the cross section of barrel bore, as it is in the case of so-called piston guns, cooperating stops for absorbing the explosive recoil forces which press the barrel against the breech are provided in the cartridge chamber or on the gun barrel. The distance between the cartridge chamber wall and across the transition range of a substantially cylindrical part adjacent the bottom edge of the cartridge itself which rests on the cartridge chamber breech is somewhat smaller than the thickness of the magazine band surrounding the transition range. This insures that a pressure is exerted on the magazine band by the wall of the barrel adjacent the cartridge chamber at a force which will not be sufficient to destroy it, but which will be high enough to seal it. According to this characteristic of the invention, care is taken that the plastic band of the magazine is protected from excessive impact loads which might occur when the barrel is directed opposite to the firing direction by the reaction forces of the explosion pressure which act upon it. At the same time, care is taken that the gas pressure will not escape around the magazine material and the cartridge chamber or between the magazine and the cartridge. To accomplish this a compressive stress sufficient for sealing purposes is provided by the dimensions of the magazine and the location of the magazine relative to the barrel in the breech. The construction is such that the breech includes an annular portion which fits into an annular recess of the barrel and a stop is formed by abutment of the ledge of the barrel with the annular portion of the breech and also by the magazine material which is disposed between an annular portion directly surrounding the cartridge chamber at the barrel and an interior annular portion surrounding the cartridge. The configuration of the parts is such that the forces acting between the cartridge chamber breech and the cartridge chamber are concentrated primarily on the region of the cross section of the cartridge bottom. To facilitate this, the cartridge chamber breech which is directly in alignment with the base of the cartridge is formed with a raised or bulbous portion so that contact in this area takes place at the first instance. The construction insures that little effort will be required to press the cartridge against the cartridge chamber and a minimum ignition energy and optimum gas effect can be achieved.

Accordingly, it is an object of the invention to provide an improved gun construction in which a sealing is effected between the material of a bandlike magazine and the barrel defining the cartridge chamber.

A further object of the invention is to provide a gun having a housing in which a barrel is axially movable, the barrel defining a cartridge chamber at its rearend which moves toward and away from a fixed breech carrying a firing pin, and an improved magazine band construction therefor having a plurality of cylindrical projections on one side which surrounds the bottom portion of each cartridge, permitting the forward tip to project forwardly for orientation into the cartridge chamber of the barrel; the barrel in the breech and the cartridge being shaped so that a sealing is provided between the barrel and the material of the magazine and wherein the breech includes a portion surrounding the barrel providing a stop so that the forces acting on the magazine will be at the desired level for sealing without rupturing of the magazine material.

A further object of the invention is to provide a gun which is simple in design, rugged in construction, and economical to manufacture.

The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which there are illustrated and described preferred embodiments of the invention. i

BRIEF DESCRIPTION OF THE DRAWINGS- In the drawings: FIG. 1 is a longitudinal sectional view through a gun constructed in accordance with the invention with a magazine inserted therein;

FIG. 2 is a section taken on the line "-11 of FIG. 1;

FIG. 3 is an enlarged sectional view of a portion of the gun indicating diagrammatically the dimensional characteristics of the barrel breech and magazine when a cartridge is in position on a slightly enlarged scale; and

FIG. 7 is a section taken along the line VII-VII of FIG. 6.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, in particular, the invention embodied therein as indicated in FIGS. 1 and 2 comprises a housing 1 having a forward end defining a forward chamber 1a in which is slidable a barrel 2. The forward end of the barrel carries a stand plate or tube 3 which is adapted to be pressed against the receiving material for the purposes of orienting the gun in respect thereto for driving an anchoring element into the material. The barrel 2 and a drive piston 4 located within the barrel move axially backwardly and forwardly during the sequence of operations under the force of the explosive gases produced by explosion of each cartridge 5 contained in a magazine generally designated 17.

The rear end of the barrel 2 is provided with an outwardly flared cartridge chamber 6 which is formed in a cylindrical extension 30. The cylindrical extension 30 is surrounded by an annular shoulder 30a.

A cartridge 5 which is located in each one of a plurality of cylindrical projections 17 on the magazine 17 is oriented with its tip pointed toward the chamber 6, and, as indicated in FIG. 1, the belt is in position to fire the uppermost one of the cartridges 5 which is aligned with the cartridge chamber. The cartridge 5 is ignited by a firing pin 7 which is carried in a fixed breech 31. As best seen in FIGS. 3 and 4, the breech 31 includes a raised central portion 31a. The firing pin 7 is prestressed against the force of a spring 8b when the gun is pressed against the target material by depressing the stand plate 3 inwardly within the housing 1. An operating bar 9 shown in FIG. 1 in broken lines acts at its rear end on the sleeve 10 which surrounds the

compression springs

8a and 8b. Spring 80 serves to exert principally and initial stress on the barrel in the driving direction. The prestressed firing pin 7 is locked by a latch 12 which is mounted for displacement in the sleeve 10 in a direction perpendicularly to the firing pin axis. The firing pin is released when the nose 12a of the latch 12 is above the free end 13a of an angle lever 13 which is pivotally mounted on a housing journal 14. The other end 13b of the angle lever 13 is actuated by a trigger 15 to cause the end 13a to push the latch 12 which will be located above the lever end 13a when the firing pin is stressed (position not represented) to thus release the prestressed firing pin. A magazine receiving channel or duct 16 extends substantially perpendicularly to the axis of the gun barrel 2 and it is located partly within the handle portion la of the housing. The magazine is indexed upwardly in a direction of the arrow X and after the uppermost cartridge is fired, it will be moved out through a top slot defined in the housing 1. The magazine channel is provided with a groove 16a for guiding the cartridge magazine band 17. The magazine band 17 includes side portions'with alternate projections and recesses 17b arranged at fixed spaced locations along its length for facilitating the feeding thereof.

The feed of the cartridge magazine is effected in an upward direction as indicated by arrow X by a two-arm indexing lover or feed lever 18. The lever 18 is pivotally mounted about a pivot point 180 in a manner which permits arm portion 180 to move upwardly and downwardly and also inwardly and outwardly. For this purpose, the opening for the mounting of the lever 18 on pivot pin 50 is made larger than that required so that the lever will tilt in any direction. In the uppermost position indicated in FIG. 1, the arm portion 18a will next be moved laterally outwardly and then downwardly to cause the arm portion to move out of the notch 17b with which it was engaged. An arm portion 18b includes a cam surface in engagement with the barrel 2 and it is rocked during the outward movement of the barrel 2 to cause the arm portion 18a to move downwardly to the dotted line position indicated in FIG.

2. A spring 52 urges the arm portion I8a'inwardly against the.

side of the magazine but permits its withdrawal out of each notch during its downward movement. On the return movement thereof, however, the spring 52 willurge the arm portion.

18a into engagement with the next notch so that the arm portion will engage behind the widened portions 180 to lift the magazine by an amount sufficient to place the next cartridge into alignment with the cartridge chamber 6.

As shown in FIG. 3, the barrel 2 will move backwardly dur-. ing the firing cycle to engage against the breech 31 and the magazine 17. The annular extension 30 of the barrel 2 engages around the exteriorly tapered cylindrical projections 54 of the magazine 17. This position will occur when the magazine is pressed against the target material. The cartridge 5 bears with its bottom part against the central projecting portion 310 of the cartridge chamber breech 31. The barrel extension 30 is forced in the directionof the chamber breech 31 and applies a loading pressure force againstthe magazine around the tubu- Iar projections 54. The loading of the magazine part which surrounds the cartridge has a double effect: first, the cartridge chamber is sealed in a gastight manner against the reaction gases in the contact range of the cartridge chamber with the part of the magazine band 17 which surrounds the cartridge. This gastight seal extends up to the contact surface between the cartridge case and the surrounding magazine band. Second, a firm support is offered to the bottom edge of the cartridge at its base 5a so that it may accommodate the subsequent shock load of the firing pin. In this manner, a low ignition energy is sufficient since the firing pin does not have to first seal the plastic supporting the cartridge bottom edge.

As indicated in FIG. 4, immediately after firing, the explosive pressure will act on the annular surface 2b defined within the interior of the barrel 2. The gap S as shown in FIG. 3 which is located between the stops formed by the ledge 30a and the annular projecting portion of the breech 31 will be reduced to zero. Thus, after ignition, the explosive force acting on the barrel 2 is absorbed by the stops defined by the surfaces 30a and 160 and this insures that the band portion of the magazine surrounding the exploded cartridge 5 does not have to absorb this load which might otherwise deform or even destroy it. The power transmission from the barrel 2 to the breech 31 is effected now through the

stops

30a and 16c. Since it is also necessary in this phase of the operation to insure a sealing against the returning explosion gases between the cartridge chamber 6 or the barrel extension 30 and the chamber breech 31, the dimensions of the cooperating parts, that is, breech 31, magazine 17 and cartridge 6 are so adapted to each other that a relatively light compressive stress of the plastic part of the magazine 17 which surrounds the cartridge will take place as the stops 30a and 160 come in contact with each other.

As represented in FIG. 3, the distance A and B define a measured difference therebetween M of from about 0.08 to O. l 2 mm less than the thickness of the magazine band 17. This means that the material of the magazine band 17 will be compressed in this base portion at the zone Y of FIG. 4 by a pressure which cannot deform or destroy the magazine due to the small dimensional compression which will take place. The

smallest distance between the bottom edge of the cartridge and the cartridge chamber wall in the transition range Y serves as a restrictor for the plastic portion in the cartridge chamber and as a restrictor it will prevent a possible outflow of the plastic at this location underextreme pressure loads.

In the embodiment of FIG. 5, a breech 31 is provided with a central portion 31a which contacts the rear face of the magazine 17. The barrel extension 30 which carries the cartridge chamber 6 rests on the magazine part 17d without a radial support of this part.

As a magazine material, there is preferably used plastics which have a test temperature of 20 C. according to the DIN measuring method. DIN-53,453 and DIN-53,435, have a notch impact strength of 8.12 kp/cm absolute, a strength of about 300305 kp/cm at the elastic limit, an elongation of the elastic limit of about 7 to 12 percent, and a modulus of elasticity and tension in the bending test of about 10,000 to 14,000. Hydrocarbon polymers, particularly polyolefins, but also copolymers are also preferred. Thus, for example, it was found particularly expedient to use a material for the magazine in this new breech which is known under the trade name of VESTOLEN PP 5500 from the group of the polypropylenes. This material shows under the indicated test conditions a notch impact strength of about cm kplcm In addition, it has the strength of the elastic limit of about kplcm an elongation at the elastic limit of about 10 percent and a modulus of elasticity in tension in the bending test of about 12,000.

In FIGS. 6 and 7, a cartridge chamber breech 31 is provided which has an elevation 31a for supporting the cartridge 5 in the magazine 17 so that it is possible to press the cartridge 5 against the barrel extension 30a without the magazine band 17. In order to insure friction-free feed of the magazine, the elevation 31a is provided with a bevel in the feeding direction of the magazine.

Iclaim:

1. An explosive force driven device such as a gun or a tool particularly for driving anchoring elements such as nails and bolts into a hard receiving material, comprising a housing having a bore adjacent its forward end and a barrel slidable in axial directions in the bore of said housing and having an inner end terminating in a cartridge chamber, means defining a magazine channel extending transversely to the path of movement of said barrel, a magazine band adapted to carry a cartridge located in said channel with the cartridge carrying portion aligned with the cartridge chamber of said barrel, said barrel in a firing position being located to position the cartridge and a portion of said magazine within the cartridge chamber thereof, said magazine being held between said barrel and said breech and forming with said barrel and said breech a closing wall for said cartridge chamber during firing.

2. An explosive force driven device, according to claim 1, wherein said barrel includes a central rearwardly projecting portion at its inner end terminating in said cartridge chamber and having an annular shoulder'formed therearound, said breech having an annular projecting portion adapted to engage against said annular shoulder in a firing position and to stop the rearward movement of said barrel, said magazine being of a thickness so that a portion located around said cartridge and extending between said central projecting portion of said barrel and said breech is compressed to form a seal therebetween when the annular projecting portion of said breech engages against the annular shoulder of said barrel.

3. An explosive force driven device, according to claim 1, including stop means defined between said barrel and said breech limiting the rearward movement of said barrel toward engagement with said breech, said stop means being such that the material of said magazine is engaged under little pressure between said barrel and said breech to aid in sealing said cartridge chamber during firing.

4. An explosive force driven device, according to claim I,

wherein said barrel includes a cartridge chamber having walls which diverge outwardl toward the inner end of said barrel, said barrel cartridge c amber and said breech being con structed such at that the contacting forces acting between said cartridge chamber barrel and said cartridge chamber breech in a firing position are concentrated primarily adjacent the location of the cartridge bottom.

5. An explosive force driven device, according to claim 4, wherein said breech includes a raised central portion projecting outwardly toward said barrel at a location to directly contact the bottom of a cartridge position in said magazine.

6. An explosive force driven device, according to claim I, wherein said barrel includes a central axially projecting portion and an annular shoulder surrounding said projecting portion, said cartridge chamber being defined within said central projecting portion, said breech having an annular projecting portion engageable with said annular shoulder of said barrel and providing a stop for the rearward movement of said barrel in a firing position, said magazine being a resilient band having a portion disposed between said central projecting portion and said breech and a tubular portion engaged by the wall of said cartridge chamber, said breechhaving a raised central portion projecting against said magazine at the location thereof which is adapted to carry the bottom of said cartridge, the distance of the rear end of said cartridgechamber from the surface of said raised central portion of said breech being about l/l 0th of a millimeter smaller than the spacing of said magazine band between two adjacent cartridges.

7. An explosiveforce driven device, according to claim 6, wherein said magazine band comprises a plastic material.

8. An explosive force driven device, according to claim 6, wherein said plastic material of said magazine is a polyolefin.

9. An explosive force driven device, according to. claim 7, wherein said magazine is a polyethylene plastic.

10. An explosive force driven device, according to claim 7, wherein said magazine is a polypropylene plastic. j

11. An explosive force driven device such as a gun or tool particularly for driving anchoring elements such as nails and bolts into a hard receiving material, comprising a housing having a bore adjacent its forward end and a barrel slidable in axial directions in the bore of said housing and having an inner end terminating in a cartridge chamber, means defining a magazine channel extending transversely to the path of movement of said barrel, a magazine band of resilient material adapted to carry a cartridge and including a portion adapted to surround the lower portion of a cartridge located in said channel with the cartridge carrying portion aligned with the cartridge chamber of said barrel, said barrel in a firing position being located to position the cartridge in a portion of said magazine within the cartridge chamber thereof, said magazine being held between said barrel and said breech and forming with said barrel and said breech a closing cover for said said cartridge chamber during firing.

12. An explosive force driven device, according to claim 1 I, wherein said barrel includes a central rearwardly projecting portion at its inner end terminating in said cartridge chamber and having an annular shoulder formed therearound, said breech having an annular projecting portion adapted to engage against said annular shoulder in a firing post position and to stop the rearward movement of said barrel, said magazine being of a thickness so that a portion located around said cartridge and extending between said central projecting portion of said barrel and said breech is compressed to form a seal therebetween when the annular projecting portion of said barre] and said breech is compressed to form a seal therebetween when the annular projecting portion of said breech engages against the annular shoulder of said barrel, said magazine being of a dimension which is great enough to provide a sealing effect but which is not great enough so that the magazine will be ruptured by the compression between said barrel and breech.

Claims

2. An explosive force driven device, according to claim 1, wherein said barrel includes a central rearwardly projecting portion at its inner end terminating in said cartridge chamber and having an annular shoulder formed therearound, said breech having an annular projecting portion adapted to engage against said annular shoulder in a firing position and to stop the rearward movement of said barrel, said magazine being of a thickness so that a portion located around said cartridge and extending between said central projecting portion of said barrel and said breech is compressed to form a seal therebetween when the annular projecting portion of said breech engages against the annular shoulder of said barrel.

4. An explosive force driven device, according to claim 1, wherein said barrel includes a cartridge chamber having walls which diverge outwardly toward the inner end of said barrel, said barrel cartridge chamber and said breech being constructed such at that the contacting forces acting between said cartridge chamber barrel and said cartridge chamber breech in a firing position are concentrated primarily adjacent the location of the cartridge bottom.

5. An explosive force driven device, according to claim 4, wherein said breech includes a raised central portion projecting outwardly toward said barrel at a location to directly contact the bottom of a cartridge position in said magazine. 6. An explosive force driven device, according to claim 1, wherein said barrel includes a central axially projecting portion and an annular shoulder surrounding said projecting portion, said cartridge chamber being defined within said central projecting portion, said breech having an annular projecting portion engageable with said annular shoulder of said barrel and providing a stop for the rearward movement of said barrel in a firing position, said magazine being a resilient band having a portion disposed between said central projecting portion and said breech and a tubular portion engaged by the wall of said cartridge chamber, said breech having a raised central portion projecting against said magazine at the location thereof which is adapted to carry the bottom of said cartridge, the distance of the rear end of said cartridge chamber from the surface of said raised central portion of said breech being about 1/10th of a millimeter smaller than the spacing of said magazine band between two adjacent cartridges.

7. An explosive force driven device, according to claim 6, wherein said magazine band comprises a plastic material.

9. An explosive force driven device, according to claim 7, wherein said magazine is a polyethylene plastic.

10. An explosive force driven device, according to claim 7, wherein said magazine is a polypropylene plastic.

12. An explosive force driven device, according to claim 11, wherein said barrel includes a central rearwardly projecting portion at its inner end terminating in said cartridge chamber and having an annular shoulder formed therearound, said breech having an annular projecting portion adapted to engage against said annular shoulder in a firing post position and to stop the rearward movement of said barrel, said magazine being of a thickness so that a portion located around said cartridge and extending between said central projecting portion of said barrel and said breech is compressed to form a seal therebetween when the annular projecting portion of said barrel and said breech is compressed to form a seal therebetween when the annular projecting portion of said breech engages against the annular shoulder of said barrel, said magazine being of a dimension which is great enough to provide a sealing effect but which is not great enough so that the magazine will be ruptured by the compression between said barrel and breech.