GB1604006A

GB1604006A - Ammunition round

Info

Publication number: GB1604006A
Application number: GB24843/78A
Authority: GB
Original assignee: Dynamit Nobel AG
Current assignee: Dynamit Nobel AG
Priority date: 1977-07-02
Filing date: 1978-05-31
Publication date: 1981-12-02
Also published as: BE868615A; FR2396266A1; IT1156846B; DE2729965A1; IT7850127A0; FR2396266B1

Description

(54) AMMUNITION ROUND (71) We, DYNAMIT NOBEL AK TIENGESELLSCHAFT, a German company, of 521 Troisdorf, Near Cologne, Germany, do hereby declare the invention for which we pray that a patent may granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to an ammunition round comprising a propellent charge and a bullet, more particularly, but not exclusively, a jacketed bullet, the bullet comprising a cylindrical bullet guide surface.

In ammunition rounds comprising jacketed bullets of the type used for relatively small and medium calibre weapons, it is usual for the largest diameter part of the bullet to be determined by the cylindrical bullet guide surface which guarantees the transmission of spin required in the barrel to the bullet.

Bullets for larger calibre weapons are generally produced by machining or forming from a high strength material, for example steel. Such bullets are provided with a separate rotating band formed of a material which is compatible with longest possible service life of the weapon barrel and which is used for transmitting spin in the barrel. Both jacketed bullets and bullets having a separate rotating band are inserted into the neck of a propellent charge case placed at their rear end and are fixed therein by twisting, rolling or otherwise engaging the neck in one or more grooves formed on the periphery of the bullet. In the case of caseless ammunition, the bullet is secured by engaging at least one annular bead of the propellent charge, which is usually a cast charge, in the corresponding peripheral groove of the bullet.

One disadvantage encountered above all in bullets, particularly jacketed bullets, for caseless ammunition is that, during the movement of the bullet from the cartridge chamber to the point at which it enters the actual barrel, the combustion space present behind and around the bullet is only incompletely sealed off. This adversely and uncontrollably affects the combustion of the propellent charge powder. Moreover, some of the propellent.

gases can flow off forwardly past the bullet through the barrel. These adverse internalballistic phenomena in turn adversely affect the external-ballistic behaviour of the bullet.

In particular, precision, i.e. the accuracy of firing, is reduced.

Another disadvantage of such a bullet is that it has to be provided with at least one peripheral groove in addition to the separate rotating band which may be present to enable it to be securely held in the propelling charge or case thereof. This does not, however, contribute anything towards improving the sealing of the combustion space in the barrel.

According to the present invention, there is provided a round of ammunition incorporating a bullet having an ogival forward region and a cylindrical guide surface which corresponds to the calibre of the bullet, in its diameter, and extends over most, but not all, of the remainder of the length of the bullet, and a propellent charge which is either an encased propellent charge or a caseless propellent charge body, the remainder of the length of said bullet comprising in the region of the rear end of the bullet an integrally formed annular enlargement, the case of a said encased propellent charge or a said propellent charge body respectively extending from rearwardly of the bullet forwardly of the bullet beyond said annular enlargement where said case or body possesses an internal diameter equal to the calibre of the bullet so as to remain in engagement with the bullet at said annular enlargement until firing of the round has taken place.

The annular collar of the bullet of an ammunition round embodying this invention may be formed integrally with the bullet when the bullet is made of an aluminium alloy, brass or mild steel, or even by forming. For example, a bullet of lead or plastics material may be produced with the annular collar according to the invention by casting or injection moulding. Such radial enlargement is formed integrally with the bullet and can be produced at low cost. This enlargement enables a simple interlocking connection to be formed, for example with propellent charge cases of metal, which, for other reasons, comprise a separately inserted base portion.The bullet can be inserted into the rear end of such a case until the front annular surface of its enlargement is in firm contact with the front wall of the case, for example in the region of its neck or shoulders to become interlocked with the case in the extraction direction. In order to make the bullet safer to handle and transport, it is best to press the rear wall of the case against the rear annular surface of the enlargement so that the bullet is also safely interlocked at its rear end.

In addition, the annular enlargement towards the rear of the bullet provides early sealing of the combustion space in the barrel in that, on firing, the annular enlargement is pressed against the wall of the transition between the cartridge chamber and the actual barrel before the bullet begins to move and effectively seals off the combustion space present behind the rear of the bullet towards the front. This improves the reaction and utilisation of the propellent charge.

The improvement in internal ballistics afforded by the annular collar of a bullet of an ammunition round embodying the invention also enables a corresponding improvement in the external ballistics of the bullet and, in particular, greater accuracy of firing to be obtained. As the bullet moves through the aforesaid transition zone, the annular collar is deformed undergoing reduction in diameter to the basic calibre of the weapon so that the travel of the bullet in the actual barrel following the transition zone is not adversely affected.

In addition, the annular enlargement of the bullet at the rear end thereof enables the transition zone of the weapon to be increased in diameter should this be of advantage for reasons associated with ordnance mechanics. In this case, too, the annular enlargement of the bullet will be adequate for the transition zone and will provide for the required early sealing effect.

In practice, the annular enlargement preferably amounts to from 2 to 15%, more preferably from 5 to 9% of the guide surface of the bullet. The enlargement will be determined in each individual case, by the internal and external ballistic requirements and by the diameter ratios of the associated barrel.

In general, the larger the calibre of the bullet, i.e. the larger the diameter of the bullet guide surface, the larger will be the enlargement.

In the case of jacketed bullets of the type used for small and medium calibre weapons, the enlargement will preferably amount to from 0.05 to 0.6 mm, more preferably to from 0.1 to 0.4 mm. The figures quoted relate to the maximum radial height of the annular enlargement or collar.

The distance between the rear of the bullet and the annular enlargement preferably amounts to from 40 % to 100% and preferably to from 50% to 70% of the diameter of the bullet guide surface, particularly in the case of jacketed bullets. However, in the case of jacketless bullets which may be produced by machining or forming, it may even be desirable to provide for a greater spacing of the enlargement from the rear of the bullet. If necessary, the optimum arrangement and construction may be determined by a few firing tests with differently constructed bullets.

The cross-section of the enlargement may be for example rectangular or arcuate. However, it is preferred that, as seen in crosssection, the enlargement has a straight front side inclined with respect to the bullet axis and oppositely inclined rear surface. The front and rear sides of this enlargement together form a double conical annulus of which the largest cross-sectional area determines the maximum enlargement. This form of enlargement has proved to be of particular value in allowing early sealing of the combustion space to be achieved as well as subsequent deformation of the enlargement to the basic calibre of the weapon. The two cone surfaces meet one another to form a charp edge in the largest common crosssectional surface. However, a slight rounding off is preferably provided here so that the transition from the front side of the rear side is gradual.

In view of the required deformation of the enlargement after it has exerted the required sealing effect, it is preferred in fact that the angle of inclination of the front surface of the bullet axis be smaller than the angle of inclination of the rear surface.

The angle of inclination of the front surface to the longitudinal axis of the bullet is preferably from 20 to 250, more preferably from 30 to 150, whilst the angle of inclination of the rear surface is preferably from 80 to 300, more preferably from 100 to 150. The smaller inclination of the front surface promotes the reduction of the enlargement to the original calibre when the bullet moves through the transition zone into the actual barrel. By contrast, the steeper inclination of the rear surface facing the rear of the bullet delays the deformation of the enlargement. By correspondingly selecting the angles of inclination, it is possible to adapt the deformation of the enlargement to meet the requirements of each individual case.

For caseless ammunition, particularly in the low calibre and medium-calibre ranges, the satisfactory anchorage of the bullet in the cast, pressed or otherwise formed propellent charge presents considerable difficulties. This anchorage is generally obtained by engaging an annular collar or retaining tongue formed on the propellent charge in a corresponding groove formed in the periphery of the bullet.

However, due to the small axial dimensions of the retaining tongue of the propellent charge which is itself of relatively low strength, this method of fixing only withstands comparatively low mechanical stressing. This gives rise to difficulties where caseless ammunition of such type is used in automatic weapons having a high firing rate where very considerable acceleration forces occur when the ammunition is fed into the cartridge chamber.

Accordingly, with such ammunition it is necessary to obviate these disadvantages, i.e.

to secure the bullet satisfactorily and as firmly as possible in the propellent charge.

The annularly enlarged bullet of a round of ammunition embodying this invention has also proved to be of particular advantage in that the annular enlargement serves as a retaining element for retaining the bullet in the propellent charge. The bullet engages through its annular enlargement in a corresponding annular recess provided in the case of an encased charge or in the body of a caseless propellent charge so that the two interlock with one another during casting of the propellent charge. The strength of this joint is very much greater than that achieved with other arrangements because the entire section of the propellent charge extending forwardly from the annular enlargement, which forms so to speak a retaining sleeve, is available for transmitting forces; this is in contrast to the effect of the narrow retaining tongue of the propellent charge.The shearing surface of the retaining sleeve formed by the annular enlargement is several times greater than that of the usual retaining tongues and, accordingly, is able to absorb greater forces.

The aforesaid configuration of the annular enlargement with oppositely inclined surfaces is also of advantage in this respect in that it provides for a more favourable distribution of forces in the propellent charge.

When propellent charges for caseless ammunition are produced integrally with the ammunition, for example by pressing around the annular enlargement, it is only possible to use the bullet if feed-resistant ammunition is to be obtained. In an alternative arrangement, the caseless propellent comprises a passage extending therethrough from the front end to the rear end thereof and the bullet being a bullet as aforesaid with oppositely inclined conical surfaces is intro duced into the passage from the rear end thereof to project from the front end thereof so as to be supported by said front side of its annular enlargement in the propellent charge in the vicinity of a transition of the passage to a front section having a crosssection of equal diameter to the calibre of the bullet.In this case, the bullet is introduced through the open central passage of the propellent charge starting from the firing side. The internal cross-section of the passage must of course be sufficiently large for the bullet together with its enlargement to be pushed through satisfactorily, i.e. without damaging the propellent charge. This passage merges towards the front with another bore having a cross-section of the same calibre as the bullet in which the bullet rests with its bullet guide surface. In the transition zone between the two passage sections, the bullet is supported in a definite manner by the front conical surface of its enlargement, thereby guaranteeing the required feed resistance.The safety of the bullet in handling and transport may be further increased by correspondingly designing the ammunition, i.e. by arranging in the bore behind the bullet further propellent charge elements sup porting the bullet at its rear end.

The annular enlargement on the bullet of a round embodying this invention has another application with cased ammunition.

With such cased ammunition, i.e. ammuniton having a case made of plastics material particularly thermoplastic plastics material for example, polyethylene or polypropylene, the bottom of the case is preferably made separately from metal or plastics material. With such cases the firm anchorage of the conventional peripherally grooved bullets pre sents difficulties because in this case, too, the case has to engage in the peripheral groove through a corresponding retaining tongue.

However, it is an expensive procedure to provide a retaining tongue such as this in the region of a neck of the case. In addition, the retaining tongue is once again only of comparatively low shearing strength.

These disadvantages are avoided if, according to another feature of the invention the cased ammunition comprises a plastics case open at one end thereof and a bullet embodying this invention projects from this end of the case, being held by means of its annular enlargement in the vicinity of a neck portion or a shoulder of the case where the case undergoes a reduction in cross-section to the calibre of the bullet. Thus, the enlargement is again a retaining element. In a preferred variant, where the case has a separately formed base portion, the bullet is introduced into the case at its bottom end until it has reached its predetermined position.

The enlargement may be situated in the region of the neck or even the shoulder of the case. In the latter case, retaining dogs, a retaining ring or the like formed on the inside of the shoulder ensure that an interlocking connection is obtained in this case too. By inserting the bullet from the bottom rather than from the mouth of the neck, the constituent material of the neck is prevented from being undesirably excessively stretched on insertion of the rear of the bullet carrying the annular enlargement, thereby reducing the extent to which the material is stretched on insertion of the bullet. After the bullet has been inserted, the propellent charge powder is introduced in the usual way, after which the base portion is inserted into the case.However, if the bullet cannot be inserted from the base, it would of course also be possible to insert it into the neck or shoulder of the case from the mouth thereof.

The bullet of a round of ammunition embodying this invention may be jacketless, being made by forming or machining, for example from light metals, for example aluminium, mild steel or lead or from plastics, for example, polyethylene or polypropylene.

This application is not limited to certain calibres. However, it is with jacketed bullets which at present range from about 3 to 15 mm in calibre that ammunition rounds of the invention are of particular value. With these jacketed bullets, the enlargement is preferably formed by compressing the bullet after jacketing thereof. The basic jacketed bullet can be formed by known processes. The compression of the bullet may be achieved by applying pressure to the rear of the bullet in such a way that its jacket and the bullet core are deformed accordingly. This may even be done in a mould provided with an annular space for forming the enlargement.

The enlargement obtained in this way is preferably situated at a distance from the bottom of the bullet of from about 40 to 100%, more preferably from about 50 to 70Oó of the calibre of the bullet.

For a better understanding of this invention and to show how the same can be carried into effect, reference will now be made, by way of example only, to the accompanying drawings, wherein: Figure la shows a jacketed bullet half in longitudinal section and half in elevation; Figure 1b shows the detail Z of Figure la on a larger scale; Figure 2 shows the fixing of a conventional bullet in a propellent charge; Figures 3 to 5 shows the fixing of a bullet to produce an ammunition round embodying this invention in a propellent charge; and Figures 6 and 7 show the fixing of a bullet in a case to produce an ammunition round embodying this invention.

Referring to Figures la and 1b of the drawings, a solid-jacketed bullet shown on an enlarged scale in Figure la, comprises a core 1 formed, for example of lead, and a jacket 2, for example of steel, fitted over the core and held thereon by compression from the rear end or base 3 of the bullet.

The bullet comprises a radial enlargement 4 which extends uniformly over the entire periphery of the bullet and is arranged in the region of the rear end of the cylindrical bullet guide surface which has the reference numeral 5. For a calibre of 4.9 mm for example, the maximum enlargement at 4, i.e. the maximum projection to one side of the bullet guide surface 5, amounts for example to 0.07 mm. The distance between the maximum enlargement and the rear end 3 of the bullet amounts to approximately 450/, of the calibre of the bullet. At its front end, the bullet guide surface 5 merges smoothly into an ogive 6. In the interests of clarity, the drawings illustrating the bullet in elevation show the various surface sections to merge smoothly with one another, i.e. without a pronounced edge.The positions at which they are separated from one another both here and in the other figure are emphasised for such reasons of clarity by peripheral lines which terminate at a distance from the outline of the bullet.

In the case of transitions having a more marked inflexion or a distinct edge, the corresponding peripheral lines are extended to the profile of the bullet in the usual way.

Thus, as shown more clearly in Figure lb, the enlargement 4 is formed by a straight front surface 7 and a straight rear surface 8. In this case, the front surface 7 is inclined at an angle a of 40 with respect to the longitudinal axis of the bullet, whilst the angle of inclination ,B of the rear surface 8 is 110. The junction 9 between the two surfaces 7 and 8 is not sharpedged, but slightly rounded off. The rounding off has proved to be of value in the anchoring of the bullet, as shown in Figures 3 to 6, because, in this way, stress concentrations are avoided or at least largely reduced both in a propellent charge and in a case therefor with which the bullet is employed.The rear surface 8 merges smoothly with a rear cone 10 of the bullet which is followed in turn by a rounded edge 11 leading to the rear end 3 of the bullet. If the rounded edge 9 is disregarded, the straight sides 7 and 8 can be seen to form a double cone.

In the interests of simplicity of the drawings, Figures 2 to 7 show bullets in elevation and divided lengthwise, with only half of the bullet and the propellent charge or the case, as the case may be, being illustrated. The other half (not shown) will be identical with the illustrated half.

Figure 2 shows the conventional anchorage of a bullet 12 in a caseless propellent charge 13, shown in part only, the bullet being housed in a central bore 14 of the propellent charge.

The bullet 12 comprises a retaining groove 15 in which the propellent charge 13 engages in form-locking manner through its annular retaining ridge 16. This anchorage is not satisfactory for caseless ammunition because, owing to the relatively small shearing surface, 17 shown as a broken line, the retaining tongue 16 is only able to absorb light axial forces indicated by the arrows F.

By way of contrast, Figure 3 shows the anchorage of the bullet 12 in caseless ammunition to produce a round embodying this invention. The bullet 12 which may be a solidjacketed bullet, is again inserted into the central bore 14 of the cast or pressed caseless propellent charge 13 and, engages through it radial enlargement 4, in formlocking manner in the correspondingly shaped propellent charge 13. Since the shearing surface 18, again shown as a broken line, is very much larger than in Figure 2, corresponding heavier axial forces F' can be satisfactorily absorbed by this anchorage achieved with a bullet according to the invention. Accordingly, the holding force is very much greater than in the anchorage shown in Figure 2.

Figure 4 shows an alternative bullet in an ammunition round embodying this invention, the bullet comprising an enlargement 4 in combination with a conventional annular groove 19 in which the propellent charge 13 again engages in form locking manner through a retaining tongue 20.

Figure 5 shows part of an integral, for example pressed, caseless propellent charge 13 having a bore 21 of relatively large crosssection extending from the firing side of a bullet 12. Only the front region of the bore 21 has been shown. This bore 21, whose cross-section is equal to or only slightly larger than that of the enlargement 4, merges forwardly with a bore 22 of equal calibre with whose wall the bullet 12 is in contact through its bullet guide surface 5. Between the two bores is a shoulder 23 on which the bullet 12 inserted into the bore 21 from the rear is supported at its front end by means of the front annular side 7 of its annular enlargement 4. This support guarantees the necessary feed resistance.Further propellent charge elements (not shown) in the bore 21 may rest on the rear end 3 of the bullet to additionally hold the rear end 3 of the bullet in place. These additional propellent charge elements may be formed by tightly packed propellent charge powder.

In the arrangements shown in Figures 6 and 7, a bullet 12 is accommodated in a cartridge case 24 of formed plastics material for example, polyethylene or polypropylene.

The base portion (not shown) of the case is separately made from metal or plastics material and accommodates the firing element. With ammunition of this type, a bullet 12 embodying this invention is inserted into the case from the bottom thereof being pushed forwards until as shown in Figure 6 its annular enlargement 4 is situated in the region of a neck portion 25 of the case joined to the main portion of the case by a shoulder 27 and terminating in an end 26. By virtue of its elasticity, the originally cylindrical neck portion 25 of the case undergoes slight internal expansion in the section in contact with the enlargement 4 so that a form-locking connection between the bullet 12 and the case 24 is achieved. Here, too, the oppositely inclined configuration of the surfaces of the annular enlargement 4 again provides for a favourable distribution of forces in the neck of the case.

A section 25' of the neck 25 situated behind the enlargement 4 of the bullet 12 is generally shorter than a neck section 25" facing towards the necks mouth 26. It is because of this dimensioning of the neck, that it is desirable to insert the bullet into the case 24 from the base thereof in order to limit the temporary elastic expansion of the neck 25 to as small a section as possible. In this way, the strength of the form-locking and friction-locking connection between the bullet 12 and the case 24 is further improved be cause, in this case, the section 25" of the neck 25 of the case is in frictional contact with the bullet guide surface 5 without undergoing any unnecessary temporary expansion.

Referring finally to Figure 7, there is shown a bullet 12 projecting from a cartridge case 24 of the type shown in Figure 6. The bullet is held in form-locking manner in the vicinity of the shoulder 27 of the case by means of its enlargement 4. For this purpose, the shoulder 27 is integrally formed on its inside with a retaining collar 28 which is shaped to match the enlargement 4 in such a way that the bullet 12 is firmly anchored at its annular enlargement 4 between the retaining collar 28 and the rear end of the neck 25. In this case, too, the bullet is again preferably inserted into the case 24 from the rear end.

After the bullet 12 has been inserted in a cartridge case as shown in Figure 6 or 7, the propellent charge is introduced in known manner into the case 24 which is then dosed by inserting its base portion thereinto. With this type of ammunition, just as in the case of the caseless ammunition illustrated in Figures 3 to 5, the annular enlargement of the bullet of ammunition embodying this in vention again enables a considerable improvement in feed resistance to be obtained in automatic weapons.

WHAT WE CLAIM IS:- 1. A round of ammunition incorporating a bullet having an ogival forward region and a cylindrical guide surface which corresponds to the calibre of the bullet, in its diameter, and extends over most, but not all, of the remainder of the length of the bullet, and a propellent charge which is either an encased propellent charge or a caseless propellent charge body, the remainder of the length of said bullet comprising in the region of the rear end of the bullet an integrally

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

light axial forces indicated by the arrows F.

By way of contrast, Figure 3 shows the anchorage of the bullet 12 in caseless ammunition to produce a round embodying this invention. The bullet 12 which may be a solidjacketed bullet, is again inserted into the central bore 14 of the cast or pressed caseless propellent charge 13 and, engages through it radial enlargement 4, in formlocking manner in the correspondingly shaped propellent charge 13. Since the shearing surface 18, again shown as a broken line, is very much larger than in Figure 2, corresponding heavier axial forces F' can be satisfactorily absorbed by this anchorage achieved with a bullet according to the invention. Accordingly, the holding force is very much greater than in the anchorage shown in Figure 2.

Figure 4 shows an alternative bullet in an ammunition round embodying this invention, the bullet comprising an enlargement 4 in combination with a conventional annular groove 19 in which the propellent charge 13 again engages in form locking manner through a retaining tongue 20.

Figure 5 shows part of an integral, for example pressed, caseless propellent charge 13 having a bore 21 of relatively large crosssection extending from the firing side of a bullet 12. Only the front region of the bore 21 has been shown. This bore 21, whose cross-section is equal to or only slightly larger than that of the enlargement 4, merges forwardly with a bore 22 of equal calibre with whose wall the bullet 12 is in contact through its bullet guide surface 5. Between the two bores is a shoulder 23 on which the bullet 12 inserted into the bore 21 from the rear is supported at its front end by means of the front annular side 7 of its annular enlargement 4. This support guarantees the necessary feed resistance.Further propellent charge elements (not shown) in the bore 21 may rest on the rear end 3 of the bullet to additionally hold the rear end 3 of the bullet in place. These additional propellent charge elements may be formed by tightly packed propellent charge powder.

In the arrangements shown in Figures 6 and 7, a bullet 12 is accommodated in a cartridge case 24 of formed plastics material for example, polyethylene or polypropylene.

The base portion (not shown) of the case is separately made from metal or plastics material and accommodates the firing element. With ammunition of this type, a bullet 12 embodying this invention is inserted into the case from the bottom thereof being pushed forwards until as shown in Figure 6 its annular enlargement 4 is situated in the region of a neck portion 25 of the case joined to the main portion of the case by a shoulder 27 and terminating in an end 26. By virtue of its elasticity, the originally cylindrical neck portion 25 of the case undergoes slight internal expansion in the section in contact with the enlargement 4 so that a form-locking connection between the bullet 12 and the case 24 is achieved. Here, too, the oppositely inclined configuration of the surfaces of the annular enlargement 4 again provides for a favourable distribution of forces in the neck of the case.

A section 25' of the neck 25 situated behind the enlargement 4 of the bullet 12 is generally shorter than a neck section 25" facing towards the necks mouth 26. It is because of this dimensioning of the neck, that it is desirable to insert the bullet into the case 24 from the base thereof in order to limit the temporary elastic expansion of the neck 25 to as small a section as possible. In this way, the strength of the form-locking and friction-locking connection between the bullet

12 and the case 24 is further improved be cause, in this case, the section 25" of the neck 25 of the case is in frictional contact with the bullet guide surface 5 without undergoing any unnecessary temporary expansion.

Referring finally to Figure 7, there is shown a bullet 12 projecting from a cartridge case 24 of the type shown in Figure 6. The bullet is held in form-locking manner in the vicinity of the shoulder 27 of the case by means of its enlargement 4. For this purpose, the shoulder 27 is integrally formed on its inside with a retaining collar 28 which is shaped to match the enlargement 4 in such a way that the bullet 12 is firmly anchored at its annular enlargement 4 between the retaining collar 28 and the rear end of the neck 25. In this case, too, the bullet is again preferably inserted into the case 24 from the rear end.

After the bullet 12 has been inserted in a cartridge case as shown in Figure 6 or 7, the propellent charge is introduced in known manner into the case 24 which is then dosed by inserting its base portion thereinto. With this type of ammunition, just as in the case of the caseless ammunition illustrated in Figures 3 to 5, the annular enlargement of the bullet of ammunition embodying this in vention again enables a considerable improvement in feed resistance to be obtained in automatic weapons.

WHAT WE CLAIM IS:- 1. A round of ammunition incorporating a bullet having an ogival forward region and a cylindrical guide surface which corresponds to the calibre of the bullet, in its diameter, and extends over most, but not all, of the remainder of the length of the bullet, and a propellent charge which is either an encased propellent charge or a caseless propellent charge body, the remainder of the length of said bullet comprising in the region of the rear end of the bullet an integrally

formed annular enlargement, the case of a said encased propellent charge or a said pro pellent charge body respectively extending from rearwardly of the bullet forwardly of the bullet beyond said annular enlargement where said case or body possesses an internal diameter equal to the calibre of the bullet so as to remain in engagement with the bullet at said annular enlargement until firing of the round has taken place.
2. A round as claimed in claim 1, in which the bullet is a jacketed bullet.
3. A round as claimed in claim 2, in which the bullet has a calibre of from 3 to 15 mm.
4. A round as claimed in claim 2 or 3, wherein the jacket is formed of steel.
5. A round as claimed in any one of claims 2 to 4, wherein the annular enlargement of the bullet has been formed by compressing the bullet at its base.
6. A round as claimed in any one of the preceding claims, in which the bullet is formed of aluminium, mild steel, lead or plastics material.
7. A round as claimed in any one of the preceding claims, wherein the annular enlargement of the bullet amounts to from 2 to 15 /ó of the diameter of the bullet guide surface.
8. A round as claimed in claim 7, wherein the annular enlargement of the bullet amounts to from 5 to 9% of the diameter of the bullet guide surface.
9. A round as claimed in claim 7 or 8, when appended to claim 3, wherein the annular enlargement of the bullet extends radially by from 0.05 to 0.6 mm.
10. a round as claimed in claim 9, wherein the annular enlargement of the bullet extends radially by from 0.1 to 0.4 mm.
11. A round as claimed in any one of the preceding claims, wherein the distance between the rear of the bullet and the annular enlargement amounts to from 40 to 100% of the diameter of the bullet guide surface.
12. A round as claimed in claim 11, wherein said distance is from 50 to 70 / of the diameter of the bullet guide surface.
13. A round as claimed in any one of the preceding claims, wherein the annular enlargement of the bullet has in transverse cross-section, a straight front side inclined with respect to the bullet axis and an op positely inclined rear side.
14. A round as claimed in claim 13, wherein the angle of inclination to the longitudinal axis of the bullet of said front side is greater than the angle of inclination to the longitudinal axis of the bullet of said rear side.
15. A round as claimed in claim 14, wherein said angle of inclination of said front side is from 20 to 250 and the said angle of inclination of said rear side is from 80 to 300.
16. A round as claimed in claim 15, wherein said angle of inclination of said front side is from 30 to 150 and said angle of inclination of said rear side is from 100 to 150.
17. A round as claimed in any one of claims 13 to 15, wherein a rounded transition zone exists between said front and rear sides.
18. A round as claimed in any one of the preceding claims wherein the propellent charge is a caseless propellent charge body which comprises a passage extending therethrough from the front end to the rear end thereof and the bullet, being a bullet as defined in any one of claims 13 to 17, has been introduced into said passage from the rear end thereof to project from the front end thereof so as to be supported by said front side of its annular enlargement in the propellent charge in the vicinity of a transition of the passage to a front section having a cross-section of equal diameter to the calibre of the bullet.
19. A round as claimed in claim 20, wherein the portion of the passage behind the bullet is occupied by further propellent charge elements.
20. A round as claimed in any one of claims 1 to 17, wherein the caseless propellent charge is a caseless propellent charge and is pressed around a length of the bullet which includes the annular enlargement.
21. A round as claimed in any one of claims 1 to 17 wherein the propellent charge is an encased propellent charge, being encased in a plastics case open at one end thereof, with the bullet extending from said end of the case and held by means of its annular enlargement in the vicinity of a neck portion of a shoulder of the case where the case undergoes a reduction in cross-section to the calibre of the bullet.
22. A round as claimed in claim 21, wherein the plastics case comprises a separately formed base portion closing it off at its rear end.
23. A round as claimed in claim 21 or 22, wherein the bullet has been introduced into the case through an open rear end of the case.
24. A round as claimed in claim 21, wherein the bullet is held in the vicinity of the shoulder of the case, entering into an interlocking arrangement with retaining projecting means in the internal surface of the case at the shoulder.
25. An item of cased ammunition, sub stantially as hereinbefore described with reference to and as shown in any one of Figures 3 to 7 of the accompanying drawings.