WO2009153410A1

WO2009153410A1 - Weapon, device for loading the weapon, and method of sealing the weapon

Info

Publication number: WO2009153410A1
Application number: PCT/FI2009/050541
Authority: WO
Inventors: Pauli Rosvall
Original assignee: Patria Land & Armament Oy
Priority date: 2008-06-19
Filing date: 2009-06-18
Publication date: 2009-12-23
Also published as: FI20085623A0; FI20085623L

Abstract

A weapon for firing a shell (2), said weapon comprising a barrel (5) and a hollow firing chamber (6) closable by a breech block (8) for loading the shell (2). The firing chamber (6) is designed to comprise a space for a two-way open-ended support piece (1), said support piece (1) having some of its length around the shell (2) and some around the breech block (8).

Description

Weapon, device for loading the weapon, and method of sealing the weapon

BACKGROUND OF THE INVENTION

The invention relates to a weapon, a device for loading the weapon, and a method of obturating the weapon according to what is presented in the preambles of the appended independent claims 1 , 11 , 20, respectively. The invention relates specifically to a device for sealing a shell in a firing chamber, for holding the shell immovably in the firing chamber, as well as to a method of obturating a weapon as regards a breech mechanism by making use of the discussed device. The invention is particularly directed to a mortar.

PRIOR ART

The relevant type of technical field is represented by US patent 6257148, Toivo- nen et al., which discloses an arrangement for supporting a shell in a smoothbore barrel. In this technique, the shell is supported before firing in such a way that the shell has its tail fitted with a support piece for disallowing a longitudinal movement of the shell. Upon firing, the support piece is partially ruptured as the shell sets off.

There are also prior known solutions for obturating the breechblock of a breech- loading field gun or mortar in order to not direct the firing chamber pressure towards the personnel operating the weapon. One of the notable solutions is the so- called de Bange sealing, a technique reflected in US patent 4404888, Gentiluomo.

SUMMARY DESCRIPTION OF THE INVENTION

It is an object of the present invention to mitigate or even eliminate the above- mentioned problems appearing in the prior art. A problem, in general, relates to holding the shell reliably against a face of a breechblock in a smoothbore weapon unless the weapon has its barrel directed obliquely upwards (firing at high angles), in which case the shell is held by gravity against the face of the breechblock. When the weapon's barrel is lowered to less than 45 degrees relative to horizontal (firing at low angles), the shell may become slightly dislodged from the face of the breechblock and a reliable detonation of the primer of a shell propellant charge is no longer certain. Firing at low angles is used for example in direct firing to support infantry or when the weapon is forced to defend itself against enemy within close range.

A particular object of the invention is to provide a solution, which enables ensuring the discussed reliable retention of a shell against the face of the breechblock and denying a sliding dislodgement of the shell prior to a desired firing action while resolving the problem of a pressure leak past the breech mechanism caused by a pressure shock applied against the breech mechanism. This leak, induced by a gas and fire residues, is dangerous for persons operating the weapon and, as a result of fire residues, it may additionally cause scale build-up on the precision finished surfaces of the breech mechanism. This may ultimately lead to a jam-up of the breech mechanism and a disablement of the weapon.

In this application, the terms front, forward and back, rearward are employed as a rule in reference to the direction of motion, which is established as a direction upon firing a shell, i.e. front, forward stands for the outgoing direction of a shell from the firing chamber towards the muzzle of a barrel, and back, rearward stands for the opposite direction and, as such, the direction of a recoil possibly generated by firing a round.

The working examples and benefits mentioned in this specification apply, as appropriate, to both artillery and tank guns as well as to light and heavy infantry weapons, even if not always specifically pointed out. At the same time, the term shell may also stand for other, non-explosive projectiles, such as bullets or smoke charges or flares. It may also stand for hollow charges or missiles.

In the definition of firing angles, the barrel points upward at an angle. If the barrel lies within an angular range (elevation) of 45-90 degrees as measured from the horizontal plane, the question is about high-angle firing. If the firing is conducted at less than 45 degrees as measured from the horizontal plane, the question is about low-angle firing. As a rule, the traditional mortar is not used for low-angle firing. Artillery is typically able to fire at both high and low angles, depending on the situation and equipment. In this application, it is also of interest to fire at negative elevation angles, i.e. at angles below the horizontal plane. In this case, there is a defi- nite possibility of the shell becoming prematurely dislodged from its firm contact with the face of the breechblock. This is especially possible when the gun is mounted on a moving vehicle or vessel, with the gun not being statically in place. Benefits of the invention include a supporting action for the shell and an obturating effect for the breech mechanism. Because of the supporting action, the weapon can be reliably used for firing at low elevation angles. In addition, the ignition of a propellant is more reliable, because a primer included in the shell remains in a re- liable contact with or at a designed small clearance off the face of a breechblock. In addition, the support piece may enable a better centering of the primer with respect to a firing pin included in the firing mechanism and a more consistent detonation of the primers. By virtue of a pre-retention force of the support piece, the reliable ignition of a propellant is possible, because a burning front in the propellant already progresses a little while the initial pressure rises without allowing the shell to "escape" into the barrel and expanding the fire space (and reducing the pressure level), even as a result of the primer detonation force. The propellant is normally ignited by a basic charge present inside the tail, after the ignition of which the fire progresses by way of holes in a tail shaft to additional charges fitted around the tail shaft. By shaping the support piece accordingly in this regard, the mounting of additional charges can also be made more reliable as long as the additional charges are located in the region between tail fins. In this case, the support piece is able to protect the additional charges from moisture, especially if a large amount of shells are prepared or charged for heavy shelling and it starts raining prior to or during the shelling. Besides, moisture can be harmful at sea should the weapon be mounted on a vessel. Regarding the shells charged for firing, the support piece may also protect the shell primer from blows possibly coming from behind, thus improving safety.

It is a further benefit that the face of the breechblock does not require separate sealing elements which could be subject to wearing. As a rule, the support piece according to the invention has been conceived as a disposable article, thus resulting in a new, reliable and precise sealing effect for each round and thereby preventing the wear of a sealing surface facing the shell. As the shell is launched, the support piece deforms a little, yet without releasing fragments. Hence, in addition to the shell, there are no other pieces shooting in the direction of a barrel, and the barrel cannot damage for example because of a loose fragment left behind by the previous round and constituting an obstacle. The support piece is attractive in terms of its costs as can be fabricated from steel. SUMMARY DESCRIPTION OF THE DRAWINGS

The invention will now be described more closely with reference to the accompanying schematic figures, in which

FIG. 1 shows a shell capable of being fired with a weapon of the invention, FIG. 2A shows a tail of and a support piece for the shell loaded in the weapon in a view directly from the front side of a barrel, such that the figure is a truncated plan view from behind a projectile (the projectile is not shown for the sake of clarity). FIG. 2B shows a section A-A of the shell, along with its support piece, loaded in the firing chamber of a gun barrel with the breech mechanism in a closed condition.

FIG. 2C shows a detail in an enlarged scale from the location of a firing chamber sealing cone, wherein the enlarged part is marked with dashed lines in FIG. 2B. FIG. 2D shows a detail in a plan view from above the support piece at the location of a cylindrical member for the visualization of bosses, and FIG. 3 shows a support piece of the invention in a perspective view, with a portion of the firing chamber wall cut away.

In view of accomplishing the foregoing objectives, a weapon, a device for loading the weapon, and a method of obturating the weapon, according to the invention, are characterized by what is presented in the characterizing clauses of the appended independent claims 1 , 11 , 20, respectively.

The invention provides a weapon for firing a shell, said weapon comprising a barrel and a hollow firing chamber closable by a breechblock for loading the shell from breech. The invention is characterized in that the firing chamber (6) is designed to comprise a space for a two-way open-ended support piece (1 ), in said support piece (1 ) some of its length is fitted to surround the shell (2) and some of its length is fitted to surround the breechlock (8).

The invention is also directed to a support piece for a shell to be fired in a weapon, said weapon comprising a firing chamber to receive the shell for loading from breech, said shell comprising a projectile segment and a tail, said tail comprising a space for a propellant and a primer for firing the shell by means of a firing mechanism fitted in a face of a breechblock, and said support piece being adapted to retain the shell longitudinally stationary in the weapon's firing chamber prior to firing in such a way that the shell is fitted of its rear surface of its tail in abutment with the face of the weapon's breechblock. The invention is characterized in that a circular cone surface present in the support piece is adapted to obturate a firing pressure, generated in a firing process of the shell, against a sealing cone present in the firing chamber.

The invention is also directed to a method of obturating a gas pressure generated in the process of firing a shell to be fired in a weapon, said weapon comprising a firing chamber fitted in a barrel, said firing chamber being closable with a breechblock, and for said weapon a prepared shell (2) for firing, said shell (2) being fire- able by means of a firing mechanism in said weapon, said shell (2) comprising a propellant, a primer and a tail (4) with its fins. The method is characterized in that the method comprises the steps of: loading the firing chamber from breech with a shell and with a two-way open-ended support piece holding the shell and shaped to match the firing chamber, closing the breechblock, and igniting the propellant by means of the firing mechanism and the primer for generating a pressure needed for firing the shell and for further passing the pressure radially past the shell tail's fins onto an inner surface of the support piece for expanding the support piece against a wall of the firing chamber, whereby the pressure is denied a free passage by way of an outer surface of the support piece into a gap between the breechblock and the firing chamber.

In the definition of a firing chamber, the term "substantially cylindrical" refers to a right cylinder or a very slightly tapering cone. It is a common practice to use slight cones in firing chambers for facilitating extraction. In visual inspection, without measuring, the shape actually looks like a right cylinder.

In one embodiment, the weapon has its firing chamber loaded with a shell, which includes a detonator at its nose for exploding the shell at its target, a projectile with its explosives inside its case, and a tail. The tail is preferably provided with fins ca- pable of stabilizing the shell in flight. Retention of the shell at the face of the breechblock for disallowing a premature dislodgement is effected by means of a precision fabricated support piece, which squeezes the shell's tail fins with a slight interference fit by the fins' outer edges. While surrounding the shell tail, the support piece surrounds also a front end of the breechblock. The support piece and the firing chamber are also formed with a conical segment. In its tail-matching segment, the firing chamber is preferably smaller in diameter than in its breechblock-matching segment. To enable the change in diameter, the firing chamber is designed with a sealing cone which is adapted to open rearward in the firing chamber for facilitating extraction. As the shell is fired, the pressure shock generated by a basic charge and possible additional charges expands the support piece to a firm contact with the firing chamber walls, because the pressure spreads freely along the support piece's inner surfaces with the fin edges hardly opposing the spreading. The pressure is applied over a comparatively large surface area inside the support piece, providing a force action inside the support piece well sufficient for expanding the support piece. Consequently, the pressure effect inside the support piece prevents the pressure from spreading along an outer surface of the support piece towards a gap between the breechblock and the firing chamber. For enhanced obturation, the firing chamber is further provided with a sealing cone. The sealing cone can be positioned in such a way that its foremost edge is substantially flush with the face of the breechblock. In the support piece and, respectively, in the firing chamber, the matching circular conical surfaces may indeed be located further forward or even further rearward, yet in such a way that ahead of the sealing cone remains a substantially cylindrical segment and behind the sealing cone lies preferably at least a short substantially cylindrical segment.

After firing a round, the support piece is removed by means of an extractor or puller. The support piece has its rearward edge provided with a collar shaped rim readily grabbed by the puller in a reliable manner for reliable extraction. Respectively, the collar shaped rim functions as a restraint for parking the longitudinal motion, with the collar shaped rim stopping against a shoulder in the firing chamber as the shell and the support piece are pushed inside the firing chamber. Behind the sealing cone lies preferably a substantially cylindrical segment for the purpose of loading, but the sealing cone may also terminate in the collar shaped rim, whereby a substantially cylindrical segment present in the sealing cone and behind it can also be omitted without straying from the inventive idea.

According to a second embodiment, an essential feature in the preparation of a shell for positioning a support piece ahead of the tail fins is that the support piece, which has a pre-deflected arrester, is placed between a projectile segment and a tail as the projectile segment and the tail are assembled. Another option is placing the support piece between a tail shaft and tail fins in the process of assembling the same.

According to a third embodiment, the installation of a support piece in front of a shell tail is possible in such a way that an arrester at a front edge of the support piece has been deflected beforehand and additionally shaped to include axial splits matching the number of tail fins (or matching a multiple of the number). The support piece can be introduced from behind the tail in a manner that the splits coincide with the tail fins. The support piece is introduced past the fins and the bypass is followed by twisting the support piece for rotating the splits into a sector between the fins and, respectively, rotating into the coincidence with a front edge of the fins will be a smaller-diameter segment of the arrester, and a pre-holding action of the shell is possible. This way, due to a smaller diameter, the arrester's front edge can be brought past the tail fins to a position in front of the fins. The support piece can be locked in position for disallowing an undesired rotation, for example such that the arrester has its front edge provided with two small bosses for fitting the fin's front edge therebetween. The bosses can be designed in such a size and shape that the support piece can be twisted by normal manual force over or past the first boss. The second boss can be slightly larger, whereby a by-pass thereof is not easily managed by manual twisting. In addition, between the bosses may be a slight cut or recess, in which the fin's front edge can be fitted. This discussed cut or recess may also be formed with a forced rupture point, which is opened by a shell as it sets off. The cut or recess can be in such a configuration that thin plate technology has been applied to make the two above-mentioned bosses for providing the locking in a first direction and between said bosses is a cut or a recess in a direction opposite to the first direction. The support piece can be locked longitudinally in position, such that behind a point matching the fin's maximum diameter is a further small boss, which during the twisting action rotates to a position behind the fin's rear edge. For enhanced locking, this boss, located in a substantially cylindrical segment ahead of the support piece's cone, can be for example in the shape of a letter L, U, V or C, the fin having its rear edge, or a chamfered rear edge of the fin, locking in the "opening bosom" of said letter, perhaps even by a snap fit.

In the preparation process of shells according to a fourth embodiment of the inven- tion, this preparation of support pieces can be carried out by using a separate tool. The support piece is pressed by the tool for providing its front edge with a necessary collar shaped rim for the arrester after the support piece is first threaded around the tail. In this discussed method, the shell tail is first set against an anvil of the tool, whereby the shell can be vertical or horizontal. This is followed by thread- ing the support piece around the shell tail. Then, the support piece's front edge is squeezed to the engagement against the shell tail's front edge for an arrester by means of a press ring of the tool, such that the support piece's front edge has an inner diameter which is smaller than the outer diameter of the tail fins. The fore- going diameters refer to those diameters which lie in a transverse plane at the same distance from the surface of the tool's anvil in the direction towards the nose of a shell.

According to one embodiment the support piece has a section of its first length in front of the circular cone surface, which is fitted to surround the shell and a section of its second length behind the circular cone surface, which is fitted to surround the breechblock.

FULL DESCRIPTION OF THE INVENTION

Depicted in FIG. 1 is a shell according to the prior art, typically a mortar shell. The principal shell segments are a projectile segment 3, a tail shaft 14, a tail 4 with several fins 21. The shell also has a detonator in the nose and obturating rings around the projectile segment, which are precisely dimensioned and fabricated with respect to the caliber, for guiding the shell and sealing the gas pressure in order to place the shell accurately on its desired flight trajectory.

FIG. 2A shows the tail 4 of and a support piece 1 for a shell 2 in a view directly from the front of a barrel 5, such that the figure is a truncated plan view from behind the projectile segment 3 i.e. ahead of a sealing cone 10 (the projectile segment 3 is not shown for the sake of clarity). The support piece 1 encircles the shell over its entire circumference, whereby the support piece is able to obturate a gas pressure effectively as early as ahead of the sealing cone. The pressure is able to spread freely past the fins 21 onto an inner surface of the support piece 1 (shown with arrows for two sectors between the fins). The tail 4 has a space in its middle part reserved for a basic charge that has its rear end provided with a primer in a per se known manner.

FIG. 2B shows, in a section A-A designated in fig. 2A, the shell 2 along with its support piece 1 as loaded in a firing chamber 6 of the weapon's barrel 5, with a breech mechanism 8 in a closed condition. The support piece 1 has its specific space reserved in the firing chamber 6 for surrounding preferably both the shell tail 4 and the forward part of a breechblock 8. This enables providing a sealing effect over a sufficiently long distance and for achieving sufficient reliability. Besides, the support piece 1 has a beneficial guide function for guiding a forward end chamfer of the breechblock 8 in the process of closing the breech. In addition, the support piece 1 may have its inner surface and outer surface provided with a preferred coating for reducing the friction of moving elements, as well as for removing the support piece 1 and/or manipulating the breechblock 8. This coating may serve to reduce wearing, adherence (welding), and possibly even corrosion or erosion caused by firing action. The coating can be for example a copper-, nickel-, molyb- denum- or teflon-based lining. The support piece 1 is preferably manufactured in metal, for example steel, by compression molding or deep drawing. It can also be fabricated in plastics, for example by injection molding.

The support piece 1 has a restricted mobility in depth direction by virtue of a shoulder 15 present in the firing chamber 6 and a collar shaped rim 12 responding thereto. The collar shaped rim 12 enables a reliable removal of the support piece 1 by means of a puller (not shown) in a per se known manner. A hole passing through the breechblock 8 is used for transmitting a strike from the firing mechanism to a basic charge primer (not shown) present in the middle of the tail 4. After the basic charge has ignited, the wall of fire progresses through holes in the tail shaft 14 to additional charges possibly around the tail shaft 14. The number of additional charges may typically vary within the range of 0-5 and, among other things, the selection of their number can be used for adjusting a desired firing range. The attachment of additional charges is also possible by way of shaping the support piece 1.

FIG. 2C shows a detail in an enlarged scale from the location of a sealing cone 10 for the firing chamber 6, wherein the enlarged area is designated by dashed lines in FIG. 2B. Retention of the shell 2 is implemented by means of an arrester 11 , which comprises a deflected segment at the front edge of the support piece 1. The arrester 11 has been deflected to a position in front of the fins 21. In the process of firing a shell, the deflection of the arrester 11 straightens out and the shell sets off (to the left in the figure). At a maximum diameter of the fins 21 , the support piece 1 also guides and aligns the shell's 2 tail 4 for concentricity relative to the barrel or tube 5. Against the sealing cone 10 is precisely pressed a cone 16 of the support piece 1. At this point, the support piece has its end respectively provided with a chamfer which supports the cone 16 from inside. In this particular manner, as the cone 16 is dimensionally accurate, it is possible to adjust the weapon's head- space.

Because, in the process of firing a round, the gas pressure is allowed to work freely inside the support piece 1 , it is possible to provide a reliable obturation as early as ahead of the sealing cone 10. In the event that some gas pressure finds its way past the arrester's 1 1 deflection out of the support piece 1 , the by-passing gas stops at the sealing cone 10 by virtue of its precise fitting. When the shell 2 is loaded with a screw-attachment or the like breech mechanism 8, the shell 2 shall have its tail 4 supported and at the same time clamped between the support piece's 1 arrester 11 and the face of the breechblock.

FIG. 2D shows a detail in a plan view from above the support piece 1 at the foremost, substantially cylindrical segment for visualizing bosses 19 and a locking boss 20. The figure is preceded by the phase in which the support piece 1 , pro- vided with splits 22, has been threaded from behind a shell past the tail's 4 fins 21 , such that, as regards the splits 22 present at the arrester's 11 edge, the maximum diameters of fins has been successfully passed and the support piece 1 is in a correct position in terms of its length.

The figure depicts a condition, in which the support piece 1 has been successfully twisted with respect to the fin 21 to a locking position. The illustrated arrows refer to those opposite directions in which the locking has been managed. The shell 2 has had its fin 21 twisted upward and, respectively, the support piece 1 has been twisted downward until a first one of the bosses 19 pressed on the arrester 11 has by-passed the fin 21 . The fin 21 has its edge under the support piece marked in dashed lines, and more specifically therein, the area of maximum diameter for the fin 21 has been marked with a rectangle in dashed lines. When the fin 21 snap fits on the arrester 11 between the bosses 19, a lengthwise locking occurs at the same time by means of the shaped locking boss 20. In the figure, it is shown in the shape of a letter C and settles behind a location present on the maximum diameter of the fin 21. For a reliable locking of the support piece, the bosses 19 and the locking bosses 20 are needed in more locations than in coincidence with just one fin. At a maximum, the number is naturally consistent with the number of fins. The number of splits 22 is consistent with the number and pitch of fins 21 in order to manage a successful past-threading operation. All of the above-mentioned bosses 19 and locking bosses 20 are readily obtainable by thin plate technology, for example by stamping on the support piece 1.

FIG. 3 shows a support piece 1 of the invention in a perspective view, wherein a section of the firing chamber's 6 wall has been cut away for exposing essential elements of the invention. The support piece's 1 wall has also a sector cut away. The support piece 1 has its collar shaped rim 12 in plain view, and the support piece extraction is readily implementable by means of a puller (not shown). Fur- thermore, in an extracted position, the breechblock 8 can be supported by means of an articulated hinge for easier operation.

The figures only illustrate one preferred exemplary embodiment of the invention. The figures do not specifically demonstrate aspects, which are of a secondary meaning from the standpoint of the principal idea of the invention, which are known as such or per se obvious for a skilled artisan, such as power units or support frames possibly required by the invention. It is evident for a person skilled in the art that the invention is not limited to the foregoing examples alone, but that the invention is subject to variations within the scope of the appended claims. The dependent claims present a few possible embodiments of the invention and, as such, are not to be construed in the sense that would limit the scope of protection claimed for the invention.

Designations used in the figures:

1 - support piece

2 - shell

3 - projectile segment 4 - tail

5 - weapon's barrel

6 - firing chamber

7 - puller

8 - breechblock 9 - firing mechanism

10 - weapon sealing cone

11 - arrester

12 - collar shaped rim 14 - tail shaft 15 - shoulder

16 - cone

17 - tool's press ring 18 - tool's flank

19 - boss 20 - locking boss

21 - fin

22 - split

Claims

1. A weapon for firing a shell (2), said weapon comprising a barrel (5) and a hollow firing chamber (6) closable by a breechblock (8) for loading the shell (2) in the firing chamber (6) from breech, characterized in that the firing chamber (6) is de- signed to comprise a space for a two-way open-ended support piece (1 ), in said support piece (1 ) some of its length is fitted to surround the shell (2) and some of its length is fitted to surround the breechlock (8).

2. A weapon as set forth in claim 1 , characterized in that, during the process of firing, the support piece (1 ) is fitted to press tightly against the walls of the weapon's firing chamber (6) for obturating the breechblock (8).

3. A weapon as set forth in claim 2, characterized in that in the support piece (1 ) its cone (16) is fitted to press, at the latest upon firing, tightly against a sealing cone (10) fitted in the firing chamber (6).

4. A weapon as set forth in claim 3, characterized in that the firing chamber (6) comprises, in a space reserved for the support piece (1 ), a substantially cylindrical space for the support piece (1 ) forward of the sealing cone (10) in the firing cham- ber (6).

5. A weapon as set forth in claim 3, characterized in that the firing chamber (6) comprises, in a space reserved for the support piece (1 ), a substantially cylindrical space for the support piece (1 ) rearward of the sealing cone (10) in the firing chamber (6).

6. A weapon as set forth in claim 1 , characterized in that the weapon is comprising in its firing chamber (6) a shoulder (15) for limiting a lengthwise movement of the support piece (1 ), such that the support piece (1 ) is fitted with its collar shaped rim (12) in its operative position against the shoulder (15).

7. A weapon as set forth in claim 1 , characterized in that the weapon is comprising a puller (7) for extracting the support piece (1 ) from the firing chamber (6).

8. A weapon as set forth in claim 1 , characterized in that the weapon's breechblock (8) is screw-closable.

9. A weapon as set forth in any of the preceding claims, characterized in that its barrel (5) is pointable for firing at a 0-90-degree elevation angle relative to the horizontal plane or at an elevation angle which is below the horizontal plane.

10. A weapon as set forth in any of the preceding claims, characterized in that it is mountable for use on a moving chassis or a vessel.

11. A support piece (1 ) for a shell (2) to be fired in a weapon, said weapon comprising a firing chamber (6) to receive the shell (2) for loading from breech, said shell comprising a projectile segment (3) and a tail (4), said tail (4) comprising a space for a propellant and a primer for firing the shell (2) by means of a firing mechanism (9) fitted in a face of a breechblock(δ), and said support piece (1 ) being adapted to retain the shell (2) longitudinally stationary in the weapon's firing chamber (6) prior to firing in such a way that the shell (2) is fitted of its rear surface of its tail (4) in abutment with the face of the weapon's breechblock (8), characterized in that a circular cone surface present in the support piece (1 ) is adapted to obturate a firing pressure, generated in a firing process of the shell (2), against a sealing cone (10) present in the firing chamber (6).

12. A support piece (1 ) as set forth in claim 11 , characterized in that the support piece is comprising in the front side and/or rear side of its cone (16) a substantially cylindrical segment.

13. A support piece (1 ) as set forth in claim 1 1 , characterized in that, in the sup- port piece (1 ), the cone (16) is with its inner surface adaptable to a contact with a chamfer fitted in the breechblock (8).

14. A support piece (1 ) as set forth in claim 1 1 , characterized in that, in the support piece (1 ), the cone (16) is with its outer surface adaptable to a contact against a sealing cone (10) fitted in the firing chamber wall.

15. A support piece (1 ) as set forth in claim 11 , characterized in that the support piece (1 ) is comprising a collar-shaped rim (12) for bracing the support piece (1 ), such that the collar shaped rim is fitted to disallow a movement of the support piece (1 ) longitudinally against a shoulder (15) present in the firing chamber (6).

16. A support piece (1 ) as set forth in claim 15, characterized in that the support piece (1 ) is comprising a collar shaped rim (12) for extracting the support piece (1 ).

17. A support piece (1 ) as set forth in claim 11 , characterized in that the front edge of the support piece (1 ) is adapted to deflect or rupture in response to a firing pressure.

18. A support piece (1 ) as set forth in claim 11 , characterized in that the support piece (1 ) is fitted to disallow an undesired longitudinal movement of the shell (2) forward in the barrel prior to a desired firing moment.

19. A support piece (1 ) as set forth in claim 1 1 , characterized in that in said support piece (1 ) a section of its first length in front of the circular cone surface is fitted to surround the shell (2) and a section of its second length behind the circular cone surface is fitted to surround the breechblock (8).

20. A method of obturating a gas pressure generated in the process of firing a shell (2) to be fired in a weapon, said weapon comprising

- a firing chamber (6) fitted in a barrel (5), said firing chamber (6) being closable with a breechblock (8),

- and for said weapon a prepared shell (2) for firing, said shell (2) being fireable by means of a firing mechanism in said weapon, said shell (2) comprising a propel- lant, a primer and a tail (4) with its fins

characterized in that the method comprises the steps of:

- loading the firing chamber from breech with the shell (2) and with a two-way open-ended support piece (1 ) holding the shell (2) and shaped to match the firing chamber (6),

- closing the breechblock (8),

- igniting the propellant by means of the firing mechanism (9) and the primer for generating a pressure needed for firing the shell (2) and for further passing the pressure radially past the shell tail's (4) fins onto an inner surface of the support piece (1 ) for expanding the support piece (1 ) against a wall of the firing chamber (6), whereby the pressure is denied a free passage by way of an outer surface of the support piece (1 ) into a gap between the breechblock (8) and the firing chamber (6).