The present invention relates to a method and an arrangement for aligning a sub-calibre barrel inserted in a principal weapon.

Background of the invention

Training weapons with a sub-calibre barrel arranged in the barrel of a principal weapon are well-known in the art. Training weapons are used to perform training exercises with training ammunition. Typically, an insert comprising a holder or adapter for a sub-calibre barrel is inserted in the barrel of a principal weapon, e.g. for firing of shells. As in any weapon, the sub-calibre barrel needs to be accurately aligned and held in place over time such that the sight corresponds to the angle of the sub-calibre weapon in the same way as the principal weapon.

In the art, it is known through e.g. EP 163028 that sub-calibre barrels can be aligned by insertion in a holder device in a principal weapon. The sub-calibre barrel is aligned by fixing screws at the front and rear parts of the barrel. However, over time, aligning of the barrel may need adjustment which conventionally has been performed by adjusting the fixing screws in the front part of the barrel thus bending the barrel while the rear part of the barrel remains fixed.

However, adjustment of fixing screws while maintaining the rear part of the sub-calibre barrel fixed is not always a reliable long-term solution to maintain durable aligning of the sub- calibre barrel. There is thus a need to extend the period of time of accurate aligning to avoid frequent adjustment of the sub-calibre barrel.

The present invention intends to provide a new arrangement and method of adjusting the sub-calibre barrel coping with the above-mentioned problems. Moreover, the present invention provides a more convenient way of adjusting the sub-calibre barrel without bending the barrel which also prolongs the life span. The invention also intends to reduce tensions in the sub-calibre barrel. In addition, the present invention results in less need of maintenance of the sub-calibre barrel. The invention

The present invention relates to an arrangement for aligning a sub-calibre barrel for use in a principal weapon barrel comprising

i) an insert arranged in said principal weapon barrel

ii) front securing means for aligning the sub-calibre barrel

iii) rear securing means for securing the rear end of the sub-calibre barrel, wherein iii.a) said rear securing means comprise a barrel nut in which said sub-calibre barrel is inserted;

iii.b) clamping means securing said barrel nut to said insert and said clamping means in said principal weapon barrel.

It has been found the present invention extends the period of time of accurate aligning compared to the prior art that adjusts the aligning of the sub-calibre barrel by bending the front of the barrel by means of securing means such as fixing screws. Bending of the front of the barrel is not needed according to the present invention. As the front of the barrel is bent as disclosed in the prior art, a need to align the barrel occurs more frequently. It has thus been found a more convenient way of adjusting (and aligning) the sub-calibre barrel according to the present invention. Preferably, while the rear end of the sub-calibre barrel is resting, e.g. in a loosely held turnable barrel nut, e.g. a barrel nut that is not yet secured by clamping means (enabling the inserted sub-calibre barrel to turn), the unsecured front end of the sub-calibre barrel can be aligned by leaning it in the desired direction without having to bend it by the front securing means. Preferably, the front end of the sub-calibre barrel is thus aligned and subsequently secured by means of front securing means such as fixing screws and thereafter the rear end of the sub-calibre barrel is secured, e.g. by means of fixing means such as fixing screws whereby the barrel nut is secured to the rear and front clamping means and the insert. Thus, by avoiding exposure of the barrel to tensions by bending the front end thereof, the barrel of the present invention is not worn to the same extent as in the prior art. The present invention thus offers a convenient way of securing the front and the rear ends of the sub-calibre barrel. The barrel nut, clamping means, and the insert thus in conjunction ascertain the rear end of the sub-calibre barrel is secured and that the sub-calibre barrel is aligned in conjunction with the securing means at the front of the barrel.

By the term "clamping means" is comprised e.g. clamping washer. According to one embodiment, the clamping means comprise front and a rear clamping means. Suitably, front and rear clamping means may be used such as a front clamping washer and a rear clamping washer. According to one embodiment, the front and rear clamping means secure the barrel nut at either side thereof. According to one embodiment, the sub-calibre barrel is threadedly affixed in the barrel nut. The barrel nut has a length L in the axial direction of the sub-calibre barrel. According to one embodiment, the sub-calibre barrel is inserted 40 to 60 % of the length L of the barrel nut. According to one embodiment, the barrel nut has a rounded, elliptical or spheroidal exterior surface contacting the front and rear clamping means.

According to one embodiment, the surface of the clamping means in contact with the surface of the barrel nut (2) is rounded, elliptical or spheroidal (as further illustrated in figures 8c and 8d). By having rounded, elliptical or spheroidal contact surfaces of the clamping means and barrel nut, a smooth and even contact is provided safeguarding sufficient securing of the barrel nut independently of the aligning of the sub-calibre barrel. According to one embodiment, the surface of the clamping means in contact with the surface of the sub- calibre barrel nut is not rounded. According to one embodiment, the inner diameter of the clamping means is constant across its entire cross section (as further illustrated in figure 8a). According to one embodiment, the inner diameter of the clamping means is tapered across its cross section, at least at the portion of the inner diameter that is in contact with the barrel nut (as further illustrated in figure 8b). The shape of the inner diameter of the clamping means may thus vary. As long as the clamping means has a surface enabling safe securing of the barrel nut, aligning of the sub-calibre barrel may be provided. According to one embodiment, the barrel nut has an exterior rounded, elliptical or spheroidal shape to provide a contact surface corresponding to the shape of the clamping means. Preferably, the barrel nut has an exterior spheroidal shape such that its contact surface is the same independently of the aligning of the sub-calibre barrel. The barrel nut may, however, have other shapes as long as it can be secured by the clamping means. The term "screw" will when used without any further specification indicate a screw enabling fixing, i.e. a fixing screw. According to one embodiment, at least three fixing means, such as fixing screws, are tightening said front and rear clamping means and said barrel nut to each other. According to one embodiment, the front clamping means is tightened to the insert, barrel nut and rear clamping means by means of fixing screws drawn from said front clamping means.

According to one embodiment, the rear clamping means is tightened to the barrel nut, and the front clamping means by means of fixing screws drawn from the rear clamping means. According to one embodiment, six fixing screws are used to tighten the front and rear clamping means and the barrel nut to each other and to the insert. According to one embodiment, said rear and front clamping means are clamping washers.

The invention also relates to a training weapon comprising the arrangement as described herein. Preferably, the training weapon comprises an insert inside which is installed the sub- calibre barrel for subcalibre ammunition, a removable breech containing at least one holder for the sub-calibre ammunition, a firing pin, a hammer and a safety device.

According to one embodiment, the sub-calibre barrel is designed for ammunition calibres ranging from 1 to 20 mm, preferably from 2 to 13 mm. The invention also relates to a method of aligning a training weapon comprising the arrangement as described herein. The method of aligning a training weapon comprises

1) aligning the front end of the sub-calibre barrel by adjusting front securing means;

ii) securing the rear end of the sub-calibre barrel by rear securing means comprising front and rear clamping means and a barrel nut

ii.a) securing front clamping means to the insert and the rear clamping means by fixing means, e.g. by drawing fixing screws 1 ) from said front clamping means via through holes of the insert into the rear clamping means; or 2) from said rear clamping means via through holes of the insert into the front clamping means; and optionally

ii.b) securing the rear clamping means and the front clamping means by fixing means, e.g. by 1 ) drawing fixing screws from said rear clamping means into the front clamping means, or

2) drawing fixing screws from said front clamping means into the rear clamping means.

According to one embodiment, three fixing screws are drawn from front clamping means and three fixing screws are drawn from the rear clamping means.

Preferably, the front securing means are initially arranged such that the front end of the sub- calibre barrel can be easily adjusted. Preferably, and in order to safeguard the sub-calibre barrel is not bent, the rear end of the sub-calibre barrel is loosely held by the rear securing means, e.g. by allowing the barrel nut in which the sub-calibre barrel is fixedly inserted to turn as the front end of the sub-calibre barrel is leaned as desired to align it. In such embodiment, the sub-calibre barrel can be easily adjusted since the rear end of the sub- calibre barrel is not fixed but turnable with the barrel nut.

Preferably, the front of the sub-calibre barrel is aligned by means of adjustable front securing means, e.g. adjustable fixing means such as adjustable fixing screws. By means of the fixing means at the front of the sub-calibre barrel, the sub-calibre barrel can be secured with different angle or different aligning relative to the principal barrel. Preferably, the front securing means securing the front end of the sub-calibre barrel protrude through bores in the barrel of the principal weapon thus safeguarding the sub-calibre barrel is accurately aligned along the principal barrel. Additional securing means preferably attach the insert to the principal barrel in a conventional manner. Preferably, the rear securing means secure the sub-calibre barrel by means of at least three fixing means, preferably by means of at least six fixing means.

Preferably, the sub-calibre barrel is inserted halfway into the barrel nut.

Preferably, the clamping means comprises a front and a rear washer provided with holes for securing the barrel nut and the front and rear washers to one another by means of fixing screws. Preferably, in embodiments in which the fixing screws are drawn from the front clamping means, the rear clamping means is provided with threaded holes. Preferably, the insert is provided with through holes through which fixing screws drawn from the front clamping means pass and continue into the rear clamping means provided with

corresponding threaded holes. Preferably, as an alternative, fixing screws may also be drawn from the rear clamping means whereby the front clamping means need to be provided with threaded holes instead of the rear clamping means. Preferably, in embodiments in which fixing screws are drawn from the rear washer, the front washer is provided with threaded holes. Preferably, a gear ring is arranged on the sub-calibre barrel in front of the barrel nut in the firing direction. The gear ring is preferably threadedly adjustable along the sub-calibre barrel to enable re-adjustment of the insertion of the sub-calibre barrel into the barrel nut, i.e. to what extent the sub-calibre barrel is inserted into the barrel nut having a length L. The gear ring thus secures suitable insertion of the sub-calibre barrel into the barrel nut. Preferably, the gear ring is arranged such that the sub-calibre barrel can be inserted about half-way into the barrel nut, i.e. a length L/2.

Preferably, a bolt is inserted halfway into the barrel nut from the opposite side of the barrel nut, i.e. from the rear part of the barrel nut seen in the firing direction. In such embodiment, the front end of the bolt is preferably secured in the barrel nut by means of a bayonet mount adjacent to the rear end of the sub-calibre barrel. According to this embodiment, a bolt is inserted about halfway into the barrel nut from the rear end thereof (seen from the fire direction) and the sub-calibre barrel is inserted halfway into the barrel nut from the front end thereof (seen from the fire direction).

According to one embodiment, the space between the bolt and the radial surrounding of the insert is adapted to allow angling of the bolt. If the sub-calibre barrel is inclined downwards for example 1 ° relative to the principal barrel assuming the sub-calibre barrel and the principal barrel were parallel from the outset, the barrel nut will be turned accordingly and the bolt will be angled such that the space between the bolt and the surrounding insert becomes smaller. The rear end of the bolt will then no longer be coaxially oriented with the barrel of the principal weapon. Instead, the rear end of the bolt will be turned toward the upper surface of the principal barrel if the sub-calibre barrel is inclined downwards 1 °. A skilled person knows what appropriate dimensioning of the insert and securing means are needed to allow for accurate aligning. Preferably, the arrangement according to the invention is applicable to training with e.g. recoilless weapons but may be implemented in any suitable weapon type.

Brief description of the figures

Figure 1 shows a cross section of a barrel nut secured by clamping washers. Figure 2 shows a cross section of a sub-calibre barrel insert.

Figure 3 shows a perspective view of a sub-calibre barrel, barrel nut, and clamping washers.

Figure 4 shows a perspective view of the exterior surface of a spheroidal barrel nut.

Figure 5 shows an insert arrangement comprising a sub-calibre barrel.

Figure 6 shows the rear end of a barrel nut where the bolt is inserted and the rear clamping washer.

Figure 7 shows a cross section of a front arrangement for securing the front of the sub- calibre barrel by means of screws.

Figures 8a-d show cross sections of clamping means with different shapes contacting the barrel nut. Detailed description of the invention

Figure 1 shows a sub-calibre barrel 1 , the rear end of which being inserted and secured in a barrel nut 2. Barrel nut 2 is secured by clamping washers 3a and 3b. Clamping washer 3a is secured to insert (adapter) 4 and clamping washer 3b by means of tightening screws 5a. Surfaces C are exposed to pressure by clamping washers 3a and 3b to maintain the barrel nut 2 in place. Screws 5a assist in tightening the clamping washers 3a, 3b together thereby securing the barrel nut 2 and, as a consequence, sub-calibre barrel 1 . A bolt 6 inserted in the rear end of barrel nut 2 is attached by means of a bayonet mount.

Preferably, clamping washers 3a, 3b are secured to barrel nut 2 by the following procedure: Three fixing screws 5a for securing front clamping washer 3a are tightening front clamping washer 3a to insert (adapter) 4. Front clamping washer 3a and insert 4 are provided with through holes through which said three fixing screws 5a tighten insert 4 to front clamping washer 3a. Clamping washer 3b is likewise provided with corresponding holes which are threaded. Fixing screws 5a thus also tighten front and rear clamping washers 3a (which may be provided with threads) and 3b (which are provided with threads) and barrel nut 2. The fixing screws 5a are drawn from clamping washer 3a in figure 1 . However, fixing screws may also be drawn from clamping washer 3b in which case clamping washer 3a must be provided with threads to allow for tightening. Sub-calibre barrel 1 is inserted and secured in barrel nut 2. Rear clamping washer 3b, barrel nut 2, and front clamping washer 3a are provided with holes through which fixing screws 5b (not visible in fig .1 ) can be drawn from the rear clamping washer 3b to tighten it to the clamping washer 3a provided with threads whereby barrel nut 2 is held in place relative to the washers (3a, 3b) and the insert 4. Figure 2 shows a barrel nut 2 and a gear ring 7 impeding further insertion of sub-calibre barrel 1 into barrel nut 2. The ring 7 may be adjusted to modify the degree of insertion into barrel nut 2 depending on the ammunition used. Clamping washers 3 are tightened to barrel nut 2 and insert 4 by means of screws 5 thereby affixing barrel nut 2 and as a consequence sub-calibre barrel 1 . Alignment screws 8 can be adjusted to align the front end of the sub- calibre barrel 1 . The alignment screws affixing the front end of the barrel secures the aligning is maintained in the front end of the barrel.

Figure 3 shows a perspective view of a barrel 1 inserted in barrel nut 2 which is secured by clamping washers 3 by means of screws 5a, 5b. The gear ring 7 on sub-calibre barrel 1 determines the extent of insertion of the sub-calibre barrel 1 into the barrel nut 2. Figure 4 shows a perspective view of a spheroidal barrel nut 2 with a length L. Preferably, the spheroidal barrel nut has an exterior spheroidal shape to provide the same contact surface to the clamping washers irrespective of the aligning of the sub-calibre barrel 1 . For example, if the aligning of the barrel is adjusted 2° downwards, the barrel nut affixing the barrel will be turned downwards to the same extent as the barrel. Still, however, the contacting surface against the clamping washers will be the same. Therefore, clamping washers having a corresponding contacting surface against the barrel nut will always correspond and fit smoothly to the exterior surface of the barrel nut and safeguard good contacting. Figure 5 shows an insert 4 in which sealing ring 9, and membrane 13 are arranged. Sealing ring 9 holds membrane 13 in place to prevent powder gases from entering.

Figure 6 shows a barrel nut 2 from the rear end thereof. Clamping washer 3b is tightened against barrel nut 2 and clamping washer 3a (not shown) provided with threaded holes adapted for screws 5b drawn from clamping washer 3b.

Figure 7 shows fixing screws 8 adjusting and aligning sub-calibre barrel 1 .

Figures 8a-d show different cross sections of clamping means 3, typically a clamping washer, having differently shaped surfaces contacting the barrel nut 2 (compare areas C of figure 1 ). The dotted line of figures 8a-d illustrates the symmetry line (central line) of the clamping means 3. In figure 8a, only an edge of the clamping means is in contact with the barrel nut. Still, such contact may be sufficient to maintain the barrel nut fixed such that the sub-calibre barrel remains aligned in a stable way. In figure 8b, the portion of the clamping means has been tapered. This portion corresponds to the surface of the clamping means 3 that is in contact with the barrel nut 2 (compare areas C of figure 1 ). This embodiment enables a smoother contact with the barrel nut than in figure 8a which still may be sufficient. Figure 8c shows a rounded edge of the clamping means 3 in contact with the barrel nut 2 (compare areas C of figure 1 ). This also renders the contact between the clamping means 3 and the barrel nut 2 smoother than in figure 8a. In figure 8d, the whole inner surface of the clamping means 2 has been shaped to smoothly fit the barrel nut 2. While the embodiment of figure 8d may be preferred, the embodiment of e.g. figure 8a may be sufficient if the aligning of the training weapon need not be maintained for a very long period of time. An advantage of the shape of the clamping means 3 of figure 8a may be for example more cost- effective production thereof. Different embodiments may thus be selected depending on the application.