WO2012137120A2

WO2012137120A2 - Method and components for optimizing the ballistic of shotguns with smooth barrel

Info

Publication number: WO2012137120A2
Application number: PCT/IB2012/051588
Authority: WO
Inventors: Alessandro BENTIVOGLIO
Original assignee: BENTIVOGLIO ALESSANDRO & C. S.n.c.
Priority date: 2011-04-07
Filing date: 2012-04-02
Publication date: 2012-10-11
Also published as: ITBS20110044A1; WO2012137120A3

Abstract

A method for optimizing the ballistic of shots of a shot group fired by a shotgun with smooth barrel, specifically for maximizing the highest and average speed of shots, and the components for realizing such a method are illustrated. The method comprises one or more of the following steps: a) detecting the inner diameter of the bore of the barrel of the shotgun and, at a portion of the barrel free of side holes for gas exhaust, and extending inwardly substantially from the muzzle, detecting an expansion chamber having a length comprised between 5 and 15 cm and an inner diameter greater of 0.3 ÷ 1 mm than the inner diameter of the bore of the barrel of the shotgun; b) defining the inner diameter of the bore of the barrel of said gun and providing a substantially tubular choke tube, free of side holes for gas exhaust, that can be removably combined to the muzzle of the barrel, wherein at least a portion of the choke tube has a length comprised in the range of 5 - 15 cm and an inner diameter greater than the inner diameter of the bore of the barrel of 0.3 ÷ 1 mm; c) detecting the caliber of the barrel of the gun and arranging a cartridge of any one of the calibers smaller than the caliber of the barrel of the gun, and arranging a plastic sheath outside of the cartridge having a thick corresponding substantially to the difference between the cartridge and the barrel shotgun calibers; d) arranging a cartridge having a caliber corresponding to the caliber of the barrel of the gun, the cartridge comprising a case inner base, a case head and a containing tube for the shots, and providing the case inner base of the cartridge with a tubular extension, integral with the case inner base itself, wherein said tubular extension is coaxial relatively to the containing tube of the cartridge and it extends therein.

Description

METHOD AND COMPONENTS FOR OPTIMIZING THE BALLISTIC OF SHOTGUN WITH SMOOTH BARREL

DESCRIPTION

Field Of The Invention

The present invention generally relates to the field of firearms, especially the field of shotguns with smooth barrel suitable for firing shot cartridges. More specifically, the present invention relates to a method for optimizing the ballistic of the fired shots, specifically for maximizing the speed of the shots, and a kit of components for shotguns the inventive method can be implemented therewith.

The present application claims priority from the Italian Application BS201 1A000044.

State of the Art

The use of shotguns with smooth barrel for the bird hunting or sports scope, for example for the skeet shooting, is known. With the expression smooth barrel a shotgun barrel is meant whose inner bore, that is the through hole of the barrel crossed by the fired shots, is smooth.

The bore of the shotgun barrel is known to extend between a cartridge insertion chamber, usually obtained in a single piece with the barrel itself, and the outlet of the barrel, at which a choke, that gradually reduces the inner diameter of the bore of the barrel, can be present.

The national and international standardizing rules define the standardized calibers of the shotgun barrels, that is the reference standard calibers to be applied munitions, or cartridges, too.

Generally the munitions, or cartridges, fired with these shotguns are of shots type; with the term shot group the set of shots expelled from the shotgun barrel, rapidly moving towards the target, is usually meant. In the same field, interchangeable choke tubes that can be screwed to the shotgun barrel, inside or outside, with the function of reducing the inner diameter of the bore of the barrel towards the outlet according to the needs, are known to be used. The choke tubes generally have a tubular body which, in models screwed inside the shotgun barrel, is partly or fully inserted within the barrel, and in the models screwed outside the shotgun barrel increase de facto the length of the barrel.

The features of the shot group, in terms of speed of the single fired shots and space distribution thereof, are mainly affected by the geometrical features of the bore of the shotgun barrel and secondarily by other factors such as, for example, the loading contained within the cartridge, the weight and the shape of the shots, the internal geometry of the choke tube (if present), the pressure of gases produced by the exploded load of the cartridge, etc. In practice the speed of moving shots is not constant overt time and it is not the same for all the shots. Once fired almost the four fifths of the shots of a cartridge are deformed, that is it loses the spherical shape to adopt a drop shape, while losing kinetic energy and parceling out according to a swarm of shots, and the remaining part of the fired shots maintains its roundness and substantially the kinetic energy, thus becoming faster than the shots which underwent the deformation. In other terms the fired shots do not travel aligned, but they proceed in the space according to an elongate and broadened distribution, for example having the shape of an upside down pear.

At a distance of 20 meters the length of the shot group fired by a traditional shotgun with smooth barrel, calculated along a direction parallel to the path of the shots, is generally of about 2 ÷ 3 meters, that is the average distance between the first shot and the last shot of the shot group, both moving towards the target but with different speeds, is of about 2 ÷ 3 meters. This circumstance represents a drawback, since the probability of shooting a flying or moving target with the greatest number of shots is inversely proportional to the length of the shot group. In other terms a moving target that is shot by only some shots of the shot group, for example mainly the first shots, having the highest speed and kinetic energy, will have low probability of being shot by the last shots, having the smallest kinetic energy, and de facto the shots that do not succeed are wasted.

For distances greater than 20 meters the length of the shot group is even greater. For example at a distance of 35 meters from the muzzle of the same shotgun of the preceding example, the shot gun has an average length comprised in the range 4 ÷ 5 meters.

US 2,589, 171 describes a shotgun barrel and a choke tube screwed to its outlet. Between the muzzle of the barrel and the choke tube an adapter is interposed defining an expansion chamber (numeral reference 47 in figure 2) provided with an inner diameter larger of 0.12 - 0.6 mm than the inner diameter of the shotgun barrel and the greatest inner diameter of the choke tube. Next to the outlet of the barrel there are through holes (numeral reference 43) that in practice arrange the expansion chamber as an energy sink having the mere function of allowing for the rapid expansion of gases generated by the firing of the cartridge load. In other terms the gases are discharged through the holes before reaching the muzzle of the barrel, so to avoid mechanical stresses and silence the shot. Thus the gas discharge can only determine a strong reduction of the thrust exerted on the shots, that is it determines a deceleration thereof.

US 6,421 ,945 also relates to a solution wherein exhaust through holes upstream of the outlet of the shotgun barrel (shown in the figures) are provided.

Similarly, US 2,335, 138 describes a solution providing for gas exhaust openings upstream of the outlet of the barrel (numeral reference 6 in figure 1).

In view of the foregoing, since long time there is the need of optimizing the ballistic of the shot groups fired from shotguns, in terms of space distribution and highest and average speed of the shots.

Objects And Summary Of The Invention

It is therefore an object of the present invention to provide a method to solve the drawbacks of the traditional solutions, specifically a method allowing to maximize the average speed and the highest speed of the shots of the shot group fired from a shotgun with smooth barrel, minimize the length of the shot group, thus making the arrival of all the shots of the shot group on the target as simultaneous as possible, regardless from the distance between the target and the shotgun.

The shot gun produced by the fire of a cartridge loaded with traditional components in a shotgun barrel with smooth bore having traditional sizes and profiles is a shot group comprising high kinetic energy shots and low kinetic energy shots, and the latter form the tail of the shot group (the shots are distributed in the space according to a swarm having the shape of an upside down pear). The long tail shot group is, currently, considered optimal by the field experts since it would offer a high probability of striking and/ or shooting down any moving or flying target. It is a further object of the present invention to provide means that can demonstrate how much easier it is striking and/ or shooting down any moving or flying targets by minimizing the tail of the shot group.

It is yet an object of the present invention to provide means for obtaining a shot group whose space distribution can be likened to a spherical calotte.

It is a further object of the present invention to provide components or parts for shotguns with smooth barrel allowing, alone and/or in combination, to optimize the ballistic of the shot groups in the above described terms.

In its first aspect the present invention thus relates to a method, according to claim 1 , for the optimization of the ballistic of the shot groups fired from a shotgun with smooth barrel and specifically for maximizing the highest speed and the average speed of the shots of the shot group.

Specifically, the present invention therefore relates to a method for optimizing the ballistic of the shots of a shot group fired from a shotgun with smooth barrel, specifically for optimizing the speed of the shots, comprising at least one of the following steps:

a) defining the inner diameter of the bore of the barrel of said shotgun and, at a portion of the barrel free of side holes for gas exhaust and extending inside from substantially the muzzle, for a length comprised between 5 and 15 cm, defining an expansion chamber whose inner diameter is greater of 0.3 ÷ l mm than the inner diameter of the bore of the barrel;

b) defining the inner diameter of the bore of the barrel of said gun and providing a substantially tubular choke tube, free of side holes for gas exhaust, that can be removably combined to the muzzle of the barrel, wherein within the choke tube an expansion chamber is defined having a length comprised in the range of 5 - 15 cm and an inner diameter greater of 0.3 ÷ 1 mm than the inner diameter of the bore of the barrel;

c) detecting the caliber of the barrel of the gun and arranging a cartridge of any one of the calibers smaller than the caliber of the barrel of the gun, and arranging a plastic sheath outside of the cartridge having a thick corresponding substantially to the difference between the cartridge and the barrel shotgun calibers;

d) arranging a cartridge having a caliber corresponding to the caliber of the barrel of the gun, the cartridge comprising a case inner base, a case head and a containing tube for the shots, and providing the case inner base of the cartridge with a tubular extension, integral with the case inner base itself, wherein said tubular extension is coaxial relatively to the containing tube of the cartridge and it extends therein.

The steps from a) to d) can be implemented independently from each other or one in combination with at least another step.

The step a) can be easily implemented in the manufacturing of a new shotgun barrel. Nevertheless an existing shotgun barrel can also be internally rectified for implementing the step a) or, alternatively, it can be combined with a choke tube allowing the step b) to be implemented.

In practice the expansion chamber is defined by the localized increase of the inner diameter of the shotgun barrel or the inner diameter of the choke tube. The expansion chamber is free of side holes for the exhaust of the gases generated by the firing of the load contained within the cartridges. The only hole is the front one for the exit of the shots at the muzzle of the barrel.

The described arrangement allows to obtain a significant reduction of the friction between the fired shots and the inner surface of the shotgun barrel with respect to what can be observed with a similar barrel but free of the expansion chamber. In particular, between the fires shots and the inner surface of the expansion chamber a gas buffer is formed preventing the shots from contacting the inner surface of the expansion chamber itself. This feature allows to obtain a significant increase in the average speed and the instant speed of the shots fired from the shotgun barrel with respect to what can be observed with the same barrel free of the expansion chamber and with other equal conditions.

It has to be observed that in the mentioned known art documents this effect does not occur because gases are exhausted through the through holes obtained through the wall of the barrel.

Preferably the expansion chamber, circular and inside of the barrel itself, has a choke at the muzzle of the barrel. Alternatively the choke is outside of the expansion chamber.

Preferably the portion of the choke tube intended to remain distal from the muzzle of the barrel (wherein the choke tube is assembled) is provided with a choke.

More preferably the choke is at least partly tapered towards the muzzle of the barrel, or towards the muzzle of the choke tube, and the smallest inner diameter of the choke is equal to or less than the inner diameter of the bore of the barrel, that is the diameter of the portion of the barrel not comprised within the expansion chamber.

Preferably, in the step a) the inner diameter of the bore of the barrel corresponds to a standardized caliber or, alternatively, to a different diameter, that can be defined as diameter out of caliber.

Preferably in this second circumstance the inner diameter of the bore of the barrel is greater of 0.3 mm than the diameter of the corresponding standardized caliber, or it is smaller of 0.3 mm with respect to the smallest diameter of the chamber of the cartridge of the corresponding standardized caliber or it is equal to the smallest diameter of the chamber of the cartridge itself.

There are a number of advantages which can be obtained by implementing any one of the steps a) - d) and they are described hereafter relating to, respectively, a shotgun barrel, a choke tube, a case inner base and a sheath for cartridges according to independent aspects of the present invention; by simultaneously implementing two or more of the above said steps a synergistic effect can be obtained leading to further improve the ballistic of the fired shots.

In its second aspect the present invention relates to a shotgun barrel according to the claim 6. Specifically, the present invention relates to a shotgun barrel comprising a chamber for the insertion of a cartridge, an expulsion muzzle for the shots fired from the shotgun barrel and a tubular smooth bore in-between the chamber of the cartridge and the muzzle, wherein the tubular bore is free of side holes for the gas exhaust, characterized in that between the bore and the muzzle of the barrel of the shotgun there is an expansion chamber, extending for a length comprised between 5 and 15 cm, whose inner diameter is greater of 0.3 ÷ 1 mm than the inner diameter of the bore of the shotgun barrel.

In practice the expansion chamber extends from the muzzle of the barrel for a length comprised between 5 and 15 cm along the direction of the chamber of the cartridge. In other terms the expansion chamber is obtained in the final length of the shotgun barrel.

Advantageously the final expansion chamber allows to form a gas buffer between the passing shots and the chamber itself, and to minimize frictions generated between the shots and the inner surface of the barrel, with evident positive rebounds on the kinetic energy the shots maintain in their movement towards the target. In other words the described arrangement allows to maximize the speed of the fired shots.

The presence of the expansion chamber is prodromal to the shortening of the shot group, meaning that it allows to obtain a space distribution having a spherical calotte shape of the fired shots.

In other words the shots moving towards the target remain much closer to each other in the longitudinal direction rather than what is observed when employing the traditional barrels of shotgun. The shots of the shot group having a spherical calotte distribution reach the target substantially at the same time and with substantially the same speed.

It is therefore found that, compared to a traditional barrel of the same caliber, the shotgun barrel according to the present invention allows to shoot targets even far with the largest number of shots, due to the high kinetic energy held by the fired shots, to minimize the ahead spaces of the shot, and to facilitate the shots from any distance.

A further advantage consists in the notable reduction of the shot recoil that can be observed by using the shotgun barrel according to the present invention with respect to traditional solutions.

Still another advantage is given by the fact that the shot group that can be obtained with the shotgun barrel according to the present invention is wide and trimmed. For example, the Applicant verified that the amplitude of the shot group is of about 50 cm at a distance of 10 meters from the shotgun, and of about 75-95 cm at a distance from the shotgun comprised between 30 and 50 meters.

Preferably in the expansion chamber there is a choke at the muzzle of the barrel. More preferably the choke is at least partly tapered towards the muzzle of the barrel and the respective smallest inner diameter is equal to, or less than, the inner diameter of the bore of the barrel (where the expansion chamber is not present). Alternatively the expansion chamber is free of choke; in this circumstance, if present, the choke is comprised between the expansion chamber and the outlet.

The inner diameter of the bore of the barrel corresponds to a standardized caliber or it corresponds to a diameter out of caliber.

Preferably in this second case the inner diameter of the bore of the barrel is greater of 0.3 mm than the diameter of the corresponding standardized caliber, or it is equal to the smallest diameter of the chamber of the cartridge.

In its third aspect the present invention relates to a choke tube for shotgun barrel according to the claim 10.

Specifically, the invention relates to a choke tube for a shotgun barrel with smooth bore, comprising a substantially tubular body and free of side openings for the gas exhaust, that can be removably constrained to the muzzle of the shotgun barrel, characterized by comprising, inside of the body, an expansion chamber that can be crossed by the fired shots, the length of the expansion chamber being comprised in the range 5 - 15 cm and its inner diameter being greater than the bore of the shotgun barrel of 0.3÷ 1 mm.

The choke tube, of the interchangeable type, can be applied to a shotgun barrel with corresponding caliber, for example it can be screwed inside or outside of the barrel at its outlet. Although to a lesser degree, the choke tube according to the present invention allows to obtain the above described advantages relating to the shotgun barrel provided with the expansion chamber.

Preferably the choke shotgun comprises its own outlet for the shots and a choke of the expansion chamber at such an outlet. Alternatively the choke is comprised between the expansion chamber and the outlet.

More preferably the choke is at least partly tapered towards the outlet of the choke tube and the smallest inner diameter of the choke is equal to, or less than, the inner diameter of the bore of the shotgun barrel to which the choke tube can be constrained.

In its fourth aspect the present invention relates to a sheath for shotgun cartridge according to the claim 13.

Specifically, the invention relates to a sheath for shotgun cartridge loaded with shots, comprising a plastic tubular body that can be fitted outside of the cartridge, wherein the thick of the tubular body is substantially equivalent to the difference between the caliber of the cartridge and any one of the next standardized smaller calibers.

The sheath is in practice an adapter allowing to load cartridges of any one of the smaller calibers than the caliber of the barrel itself within the chamber of the cartridge of the shotgun barrel.

The effect that can be obtained by shooting a cartridge of one of the calibers smaller than the caliber of the barrel with employed smooth bore is to minimize the frictions between the shots and the barrel itself.

This allows to minimize the plastic deformations the shots unavoidably will undergo when they are fired; in other terms the sheath allows to more easily hold the roundness of the shots that, consequently, will have an optimal aerodynamic penetration and will better hold their kinetic energy along the path towards the target.

Other advantages that can be obtained with the sheath according to the invention are the shortening of the tail of the shot group and the reduced shot recoils. Further the sheath allows to maximize the speed of the fired shots, with respect to what can be observed with a cartridge of the same type, free of sheath, on equal conditions.

The short shot group, as already described, allows to shoot the target with a greater number of shots than what can be observed with a traditional cartridge on other equal conditions.

Preferably the tubular body of the sheath has an axial extension sufficient to cover outside of the case of the cartridge, that is to cover the case head of the cartridge and at least the most, or all, of the respective tube containing the shots.

In its fifth aspect the present invention relates to a case inner base of cartridge according to the claim 15.

Specifically, the invention relates to a case inner base for shotgun cartridge, comprising a plastic body, substantially cylindrical, that can be fitted in a case of the cartridge, characterized by comprising a tubular extension integral with, and coaxial relatively to, the body of the case inner base, the tubular extension being intended to be fitted inside on the containing tube for the cartridge and to contain the shots.

The obtained advantageous effect is the reduction of the tail length of the shot group with respect to a traditional cartridge on other equal conditions. In its sixth aspect the present invention therefore relates to a cartridge for shotgun, of the type comprising a case inner base, a case head and a containing tube for the shots, characterized in that the case inner base is of the above described type in connection with the fifth aspect of the invention and / or by comprising a sheath according to the fourth aspect of the invention.

In its seventh aspect, the present invention relates to a kit for shotguns with smooth barrel, characterized by comprising one or more of the above mentioned components/ parts.

In its eighth aspect the present invention relates to a shotgun provided with a smooth barrel according to the second aspect of the invention.

The components and the parts of the kit can be used alone or in different combinations.

Brief description of the drawings

More details on the invention will be evident from the following of the description made with reference to the attached illustrative and not limitative drawings, wherein:

- figures 1-3 are axial and longitudinal sectional views of corresponding shotgun barrels according to the present invention;

- figure 4 is an exploded view of a cartridge according to the present invention;

- figure 5 is an a axial and longitudinal sectional view of a sheath of according to the present invention;

- figure 6 is an axial and longitudinal sectional view of a case inner base according to the present invention;

- figure 7 is an elevation view of a choke tube according to the present invention;

- figure 8 is a scheme of a test apparatus used to test a shotgun barrel according to the present invention. Detailed Description Of The Invention

Figure 1 shows, in section, a barrel 1 of shotgun comprising a chamber 2 of the cartridge downstream of which, relatively to the forward direction of the fired shots, the bore 3 of the barrel 1 is extended. The exit of the shots from the barrel 1 occurs at the outlet 6. The barrel 1 is free of side holes for the exhaust of the gases generated by the firing of the cartridge load.

The diameter Di of the bore 3 corresponds to a standardized caliber, for example caliber twelve, that is the dimensional tolerances of the diameter Di are those accepted by the rules for that reference caliber.

Between the bore 3 of the barrel 1 and the muzzle 6 there is an expansion chamber 4 having the following geometrical characteristics relating to the bore 3 of the barrel 1 :

- the length L₄ of the expansion chamber 4 is comprised between 5 and 15 cm, more preferably between 7 and 15 cm;

the diameter D₄ of the expansion chamber 4 is greater than the diameter Di of the bore 3 according to the relationship (Di + 0.3 mm) < D₄ < (Di + 1 mm) and more preferably according to the relationship (Di + 0.3 mm) < D4 < (Di + 0.8 mm).

The expansion chamber 4 can be conceived as a broadened portion of the bore 3 of the barrel, for example obtained by rectifying the bore 3, or as an extension of the bore 3. Apart from the different phraseology, what is important is that after the shots crossed a length of the barrel with a diameter equal to the standardized caliber, they cross the expansion chamber 4 before exiting through the muzzle 6.

As shown in figure 1 , the expansion chamber 4 preferably comprises a choke 5 at the outlet 6. Alternatively the choke 5 is interposed between the expansion chamber 4 and the outlet 6.

The advantages resulting from the presence of the expansion chamber 4 are those previously described.

Figure 2 shows, in section, a barrel 1 ' of shotgun, with a smooth bore 3', wherein the inner diameter Di' of the bore 3' is out of caliber, and is specifically greater than the corresponding diameter of the standardized caliber of an amount equal to 0.3 mm, that is D₁=D₁ + 0.3 mm. This embodiment has the following characteristics:

the length L₄' of the expansion chamber 4' is comprised between 5 and 15 cm, more preferably between 7 and 15 cm;

the diameter D4¹ of the expansion chamber 4 is greater than the diameter Dr of the bore 3' according to the relationship (Dr + 0.3 mm) < D₄' < (Dr + 1 mm) and more preferably according to the relationship (Dr + 0.3 mm) < D₄' < (Dr + 0.8 mm);

the barrel also is free of side holes for the exhaust of gases. Figure 3 shows, in section, a barrel 1 " of shotgun, with a smooth bore 3", wherein the inner diameter D ¹ of the bore 3" is out of caliber, and is specifically equal to the smallest diameter of the chamber 2 of the cartridge.

This embodiment has the following characteristics:

the length L₄" of the expansion chamber 4" is comprised between 5 and 15 cm, more preferably between 7 and 15 cm;

the diameter D₄- of the expansion chamber 4 is greater than the diameter Dr' of the bore 3" according to the relationship (Dr + 0.3 mm) < D₄" < (Dr¹ + 1 mm) and more preferably according to the relationship (Di- + 0.3 mm) < D₄- < (Dr + 0.8 mm);

- the barrel 1" also is free of side holes for the exhaust of gases.

Figure 4 is an exploded and perspective view of a case 7 of a cartridge according to the present invention, comprising a case head 8, of known type, a case inner base 9 according to the present invention, and a containing tube 10 for the shots, also of known type.

Figure 6 shows the case inner base 9 in axial and longitudinal section.

The case inner base 9 comprises a plastic body 91 , substantially cylindrical, that can be fitted into the case head 8 and the tube 10 of the case 7 of cartridge. Differently from the traditional case inner bases, the case inner base 9 comprises a tubular extension 92 realized in a single piece with the body 91. Such an extension 92 fits onto the inner surface of the containing tube 10, that is the containing tube 10 and the extension 92 of the case inner base 9 are overlapped; the shots and the wad (not shown in the attached figures) are collected within the tubular extension 92 of the case inner base 9. The effect that is obtained has been described in the previous pages.

Figure 5 shows in axial and longitudinal section a sheath 1 1 according to the present invention for shotgun cartridges. The sheath 1 1 comprises a plastic tubular body 12 that can be fitted outside of the cartridge, i.e. it can be possibly fitted with a little interference, on the outer surface of the containing tube 10.

The thickness S_g of the body 12 of the sheath 1 1 is such to compensate the difference between the caliber of the cartridge and any one of the standardized smaller calibers. For example, the caliber of the cartridge is the express caliber n. 16 and the cartridge with sheath 1 1 assembled on the containing tube 10 has express caliber n. 12.

In the example shown in figure 5, the body 12 of the sheath 1 1 axially extends for a length sufficient to cover the outer surface of the whole containing tube 10 and the outer surface of the case head 8. The sheath 1 1 is a caliber adapter allowing to effectively use, in a shotgun with known caliber, cartridges with a caliber smaller than the known caliber.

Figure 7 is an elevation view of a choke tube 13 according to the present invention. Specifically, the choke tube 13 is of the inner type, that is intended to be accommodated mainly inside the shotgun barrel. The body of the choke tube 13 can be fitted in the shotgun barrel and it can be screwed to the latter by means of the thread 15. A portion 16 of the choke tube can stay outside of the shotgun barrel and it is arranged as a kind of extension.

Inside the choke tube 13 an expansion chamber 14 is obtained, equivalent to the expansion chambers 4, 4' and 4". Specifically, the expansion chamber 14 axially extends for a length comprised between 5 and 15 cm, preferably a length comprised between 7 and 15 cm. The inner diameter D of the expansion chamber 14 is greater, of at least 0. 1 mm, than the greatest inner diameter of the bore of the shotgun barrel with corresponding caliber. For example, if the greatest inner diameter of the bore 3 of the shotgun barrel is 18.9 mm, the smallest inner diameter D₁₄ of the expansion chamber 14 of the choke tube 13 is equal to 19.4 mm.

A choke tube 13 according to the present invention can also be of the outer type, that is it can be attached outside of the shotgun barrel.

What is important is that it is provided with the expansion chamber 14.

In the portion 16 intended to project from the muzzle 6 of the shotgun barrel there can be a choke (not shown in figure 7) , possibly tapered towards the muzzle 17 of the choke tube 13.

Advantageously the choke tube 13 allows to obtain the advantages of the invention by also using existing shotguns, therefore without the need of rectifying the existing shotgun barrel.

The Applicant carried out detecting tests for the speed of the shots at the "Banco Nazionale di Prova per le Armi da Fuoco Portatili e per le Munizioni Commercial? in Gardone Valtrompia (BS), Italy. The documented tests have been carried out on the dates of 07/08/ 201 1 and 07/ 22 / 201 1 . The object of tests has been to compare the obtained speed at 2.5 meters from the crown of the barrel, shooting the same typology of cartridge both in a semiautomatic shotgun barrel cal. 12 with original bore and in a shotgun barrel according to the present invention, known with the commercial name of "SUPER VELOX AB".

The ambient conditions of the test are shown in the following table:

Weapons And Munitions Used For The Tests

For carrying out the tests, the following typologies of munitions have been employed:

- "FIOCCHI" brand cartridges, "SPORTING" model, caliber 12, type 12/70, loaded with 28 g. of lead shots n. 7 ½;

- "BASCHIERI & PELLAGRI" brand cartridges, "F2 MATCH" model, caliber 12, type 12/70 loaded with 28 g. of lead shots n. 7;

-"GUALANDI" cartridges, "AX BORRA PROIETTILE" model, caliber 12, type 12/70 provided with "GUALANDI" ball of "BORRA PROIETTILE" type of 32 g.;

Tests have been carried out employing two semiautomatic shotguns, one "BERNARDELLI" brand and the other one "BENELLI" brand, both provided with two barrels, one in original arrangement and the other one modified by the Applicant according to the claimed features.

The barrels showed the following characteristics:

- "Bernardelli" barrel with original inner diameter with register n. C 18083, chamber depth of 76 mm, length of 660 m, inner diameter of 18.5 mm, cylindrical choke;

- "Bernardelli" barrel with inner profile and diameter modified by the Applicant according to the present invention, with register n. C23562, chamber depth of 76 mm, length of 660 m, inner diameter of 18.9 mm, and with a flash suppressor long 85 mm and having an inner diameter of 19.5 mm applied to the mouth;

- "Benelli" barrel with original inner diameter with register n.

C207739, chamber depth of 70 mm, length of 610 m, inner diameter of 18.4 mm and cylindrical choke;

- "Benelli" barrel with inner profile and diameter modified according to the present invention, with register n. C293076, chamber depth of 70 mm, length of 610 m, inner diameter of 18.9 mm, and flash suppressor choke having a diameter of 19.4 mm for a length of 10 cm. Conditions of The Tests

Figure 8 shows diagrammatically the employed test apparatus. After the gun has been blocked with the barrel 1 on a suitable holder, the electronic barriers 20 and 21 have been positioned at 2.5 m from the crown, as represented in the drawing below and n. 5 cartridges for each type of munitions have been shot. For the speed detection electronic barriers 20 and 21 "STAS" brand, "IRBA" model have been used, composed by two units for the interception of the bullet transit, having useful area of 1 ,000 x 1 ,000 mm, an accuracy of ± 0.2% based on 2 m and able to intercept bullets with speed comprised between 50 and 1 ,500 m/s. Barriers 20 and 21 are provided with tester to ascertain and certify their operation condition by means of the generation of signals with known amplitude.

Results

In the table below the speed averages measured during the tests are shown. Speeds are measured in meters per second m/s. speed at

2 .5 m speed at 2 .5 speed at

cartridge

Speed at 2 .5 m cartridge 2.5 m

shot with m - cartridge shot with cartridge

"Benelli" shot with "Bernardelli" shot with

Cartridge barrel

original barrel original model modified

"Bernardelli" modified "Benelli"

according barrel according to barrel

to the reg. c 18083 the invention reg.

invention reg. C23562 C207739

reg.

C293076

"FIOCCHI"

brand

cartridges,

"SPORTING"

model, caliber

373 38 1

12 , type

12 / 70, loaded

with 28 g. of

lead shots n. 7

½;

"BASCHIERI 85

PELLAGRI"

brand

cartridges, "F2

MATCH"

399 407 model, caliber

12, type 12/70

loaded with 28

g. of lead shots

n. 7

"GUALANDI"

cartridges, "AX

BORRA PROIETTILE"

model, caliber

12, type 12/70 440 449

with

"GUALANDI"

ball of "BORRA

PROIETTILE"

type of 32 g.

The test results allowed to determine that the commercial cartridges cal. 12, "FIOCCHI", "BASCHIERI & PELLAGRI" and "GUALANDI" brand, in the above stated models, shot in the barrels for semiautomatic shotgun "Bernardelli" and "Benelli" brand modified by the Applicant according to the present invention have, at 2.5 m from the crown, an average speed higher than the speed obtained by shooting the same cartridges in the barrels for semiautomatic shotgun "Bernardelli" and "Benelli" brand provided for the test, with original inner diameter.

Claims

1. Method for optimizing ballistic of shot group fired by a shotgun with smooth barrel (1 , Γ, 1") free of side holes for gas exhaust, specifically for optimizing the speed of fired shots, comprising at least one of the following steps:

a) detecting the inner diameter (Di, Di', Di") of the bore (3) of the barrel ( 1 , Γ, 1 ") of said shotgun and, at an inner portion of the barrel extending inwardly from substantially the muzzle (6), defining an expansion chamber (4) having length comprised between 5 and 15 cm and inner diameter (D₄, D₄', D₄") greater than the inner diameter (Dl , D l ', Dl ") of the bore (3) of the barrel (1 , 1 ', 1 ") of 0.3 ÷ 1 mm, wherein between said expansion chamber (4) and the passing shots a gas buffer is generated minimizing the frictions and maximizing the speed of the shots;

b) defining the inner diameter (Di, Dr, Di_") of the bore (3, 3', 3") of the barrel (1 , Γ, 1") of said shotgun and providing a substantially tubular choke tube (13), free of side openings for gas exhaust, which can be removably combined to the muzzle (6) of the barrel, provided with an expansion chamber (14) having a length comprised in the range of 5 - 15 cm and an inner diameter (Di₄) greater than the inner diameter (Di, Dr, Di-) of the bore (3) of the barrel (1 , 1 ', 1 ") of 0.3 ÷ 1 mm, wherein between said expansion chamber (14) and the fired shots a gas buffer is generated minimizing the frictions and maximizing the speed of the shots;

c) defining the caliber of the barrel (1 , Γ, 1") of the gun and arranging a cartridge of any one of the calibers smaller than the caliber of the barrel (1 , Γ, 1") of the gun, and arranging a plastic sheath (1 1) outside of the cartridge having a thick corresponding substantially to the difference from the cartridge caliber and the caliber of the barrel ( 1 , Γ, 1") of the gun; d) arranging a cartridge having a caliber corresponding to the caliber of the barrel (1 , Γ, 1 ") of the gun, the cartridge comprising a case inner base (9), a case head (8) and a containing tube ( 10) for the shots, and providing the case inner base (9) of the cartridge with a tubular extension (92), integral with the case inner base itself, wherein said tubular extension (92) is coaxial relatively to the containing tube (10) of the cartridge and it extends within the same.

2. Method according to claim 1 , wherein in said step a) the expansion chamber (4, 4', 4") is circular and inside of the barrel (1 , Γ, 1 ") itself, and wherein said expansion chamber (4, 4', 4") has a choke (5) at the muzzle (6) of the barrel ( 1 , Γ, 1 ") , and wherein in said step b) the expansion chamber ( 14) is followed by a portion (16) of the choke tube ( 13) having a choke.

3. Method according to claim 2, wherein said choke (5) is at least partially tapered towards the muzzle (6) of the barrel ( 1 , Γ, 1 ") or towards the mouth ( 17) of the mobile choke tube ( 13) and the corresponding inner smallest diameter is equal to, or less than, said inner diameter (Di, Dr, Di^») of the bore (3', 3', 3") of the barrel (1 , Γ, 1") .

4. Method according to any one of claims 1 -3, wherein in said step a) the inner diameter (Di, Dr, Dr-) of the bore (3, 3', 3") of the barrel (1 , Γ, 1") corresponds to a standardized caliber or a standardized diameter out of caliber.

5. Method according to claim 4, wherein the inner diameter (Di, Dr, Di-) of the bore (3, 3', 3") of the barrel (1 , 1 ', 1 ") is greater of about 0,3 mm than the diameter of the corresponding standardized caliber, or the inner diameter (Di, Dr, Di-) of the bore (3, 3^*, 3") of the barrel (1 , Γ, 1 ") is equal than the smallest diameter of the chamber (2) of the cartridge.

6. Barrel (1 , , 1 ") of a gun comprising a chamber (2) for inserting a cartridge, a muzzle (6) for ejecting the fired shots from the barrel (1 , Γ, 1") and a smooth bore (3, 3', 3"), in-between the chamber (2) of the cartridge and the muzzle (6), wherein the bore is free of side through holes for gas exhaust, characterized in that between the bore (3, 3', 3") and the muzzle (6) of the barrel (1 , Γ, 1 ") there is an expansion chamber (4, 4', 4"), extending for a length comprised between 5 and 15 cm, from said ejecting muzzle (6), the inner diameter (D4, D4¹, D4¹ ) thereof is greater of 0,3 (Di, Dr, Di^») of the bore (3, 3', 3") of the barrel (1 , Γ, 1") and wherein between said expansion chamber (4, 4', 4") and the passing shots a buffer of gas is generated minimizing the frictions and maximizing the speed of the shots.

7. Barrel (1 , Γ, 1 ") of a gun according to claim 6, wherein said at least one expansion chamber (4, 4', 4") has a choke (5) at the muzzle (6) of the barrel ( 1 , 1 ', 1 ") .

8. Barrel (1 , Γ, 1") of a gun according to claim 7, wherein said choke (5) is at least partially tapered towards the muzzle (6) of the barrel (1 , Γ, 1") and the corresponding inner smallest diameter is equal to, or less than, the inner diameter (Di, Dr, Dr') of the bore (3', 3', 3") of the barrel ( 1 , Γ, 1 ") .

9. Barrel ( 1 , Γ, 1") of a gun according to any one of claims 6-8, characterized by one of the following features:

- the inner diameter (D Dr, Dr') of the bore (3, 3', 3") of the barrel (1 , Γ, 1") corresponds to a standardized caliber or a diameter out of standardized caliber;

- the inner diameter (Di, Dr, Dr>) of the bore (3, 3', 3") of the barrel ( 1 , Γ, 1 ") is greater of about 0,3 mm than the diameter of the corresponding standardized caliber, or the inner diameter (Di, Dr, Dr) of the bore (3, 3', 3") of the barrel ( 1 , Γ, 1 ") is equal than the smallest diameter of the chamber (2) of the cartridge.

10. Choke tube ( 13) for a barrel ( 1 , Γ, 1 ") of a shotgun with smooth bore, comprising a body substantially tubular free of side openings for gas exhaust and that could be removably constrained to the muzzle (6) of said barrel (1 , Γ, 1") of the gun, characterized by comprising, inside said body, an expansion chamber (14) crossable by the fired shots, the length of said expansion chamber (14) being comprised in the 5 - 15 cm range and the inner diameter of said expansion chamber being greater of 0,3 ÷ 1 mm than the inner diameter (Di, Dr, D ) of the bore (3, 3', 3") of the barrel (1 , Γ, 1") of the gun.

11. Choke tube (13) according to claim 10, comprising its own outlet (17) for the shots and a possible choke of said expansion chamber (14) at said outlet (17).

12. Choke tube (13) according to claim 1 1 , wherein said choke is at least partially tapered towards the outlet (17) of the choke tube (13) and the inner smallest diameter is equal to, or less than, the inner diameter (Di, Dr, Di^») of the bore (3', 3', 3") of the barrel (1 , Γ, 1") of the gun the choke tube (13) could be constrained to.

13. Sheath (1 1) for a gun cartridge loaded with shots, comprising a tubular body (12) made of plastic material that could be fitted outside the cartridge, wherein the thick (S_g) of said tubular body (12) is substantially equal to the difference between the caliber of said cartridge and any one of the standardized lower calibers.

14. Sheath (1 1) according to claim 13, wherein said tubular body (12) has an axial extent sufficient to coat the outside of the case head (8) of the cartridge and the corresponding containing tube (10) for the shots.

15. Case inner base (9) for a gun cartridge, comprising a body

(91) in plastic material, substantially cylindrical, that could be inserted in an case head (8) of said cartridge, characterized by comprising a tubular extension (92) integral with, and coaxial to, the body (91) of the case inner base (9), said tubular extension (92) being intended to fit inside the containing tube (10) of the cartridge and contain shots and wad.

16. Gun cartridge of the type comprising a case inner base (9), a case head (8) and a containing tube (10) for the shots, characterized in that said case inner base (9) is a case inner base according to claim 15 and/or by comprising a sheath (1 1) according to any one of claims 13- 14.

17. Kit for shotguns with smooth barrel (1 , Γ, 1"), characterized by comprising one or more of the following:

- a gun barrel (1 , , 1") according to any one of claims 6-9;

- a choke tube (13) according to any one of claims 10-12;

- a sheath (1 1) for the cartridge according to any one of claims 13-

14;

- a case inner base (9) of the cartridge according to claim 15;

- a cartridge according to claim 16.

18. Gun provided with at least one barrel (1 , Γ, 1") according to any one of claims 7-9.