Historical Document · 2007
BAE Systems' patent (GB priority 27 March 2003; granted 1 May 2007) for a hard steel 4.6 mm projectile with a copper coating thick enough that the rifling engraves only the coating. The HK MP7 dive's source for the armour-piercing 4.6 × 30 bullet's construction.
US007210411B2 (12) United States Patent (10) Patent N0.: Booth et al. (54) (45) Date of Patent: 4.6 MM SMALL ARMS AMMUNITION 996,820 A * I (75) US 7,210,411 B2 1,582,673 A * Inventors: gerek 309th’ CreWe (GB)§ Adm“ avld smlth’ Crewe (GB)’ Robert Assignee; BAE Systems PIC, London (GB) (*) Notice? 7/1911 Wray ....................... .. 102/524 4/1926 Fahrenwald .............. .. 148/432 3,349,711 A * 10/1967 Darigo et a1. ............. .. 102/509 4,619,203 A * Ashley, Crewe (GB) (73) May 1, 2007 10/1986 Habbe ...................... .. 102/516 5,686,693 A 11/1997 Jakobsson 6,090,756 A * 7/2000 Brown ..................... .. 508/118 6,293,203 B1 9/2001 Alexander et a1. D456,480 s * 4/2002 Quinsa et a1. ........... .. D22/116 Subjecno any disclaimehtheteml Ofthis patent is extended or adjusted under 35 USC 154(b) by 200 days. (21) Appl. No.: 10/492,982 (Continued) (22) PCT Filed: Mar. 16, 2004 FOREIGN PATENT DOCUMENTS (86) PCT No.: PCT/GB2004/001111 § 371 (0X1), (2), (4) Date: Apr. 16, 2004 DE 309293 * 1/1920 (Continued) 87 ( ) PCT P b. N .: WO2004/085954 u 0 PCT Pub Date: Oct 7, 2004 (65) Prior Publication Data US 2004/0244630 A1 _ (30) (57) (GB) ABSTRACT Dec. 9, 2004 _ _ _ _ A round of ammunition for ?ring from a gun having a ri?ed Forelgn Apphcatlon Pnonty Data Mar. 27, 2003 (51) Primary Examinerilames S. Bergin (74) Attorney, Agent, or FirmiNixon & Vanderhye PC. barrel, especially a small arms weapon. The projectile (1) ............................... .. 03072725 forming a part of the round is of steel or other material (2006.01) (2006.01) having a Vickers Hardness value not less than 550, and has a coating (13) of copper or copper alloy. The projectile has a forward body portion (9) which has a diameter similar to that of the lands of the ri?ing, and a rearward body portion Int. Cl. F423 12/04 F423 12/78 (52) US. Cl. ..................................... .. 102/514;102/524 (3) having a diameter Which is similar to the diameter (58) Field of Classi?cation Search .............. .. 102/514, de?ned hy the roots of the ri?ing greeves- The eeatihg (13) 102/501’ 516’ 511, 517’ 524 See application ?le for Complete Search history is of a thickness not less than the depth of the said ri?ing grooves, so that the ri?ing engraves the coating but does not _ (56) signi?cantly engrave the underlying steel or other hard References Clted material. The advantages associated with a hard projectile material are thus obtained without substantially increasing U.S. PATENT DOCUMENTS barrel wear. 326,231 A * 711,209 A 9/1885 * 10/1902 847,149 A * 3/1907 Manning .................. .. 102/501 Hill . . . . . . . . . . . . . . . . .. 102/524 Barlow ..................... .. 102/524 24 Claims, 3 Drawing Sheets US 7,210,411 B2 Page 2 US. PATENT DOCUMENTS FR 2 511 497 {31 102/518 FR 2540239 A Carter uge ......... .. . 102/507 GB 697172 9/1953 12/2005 McElroy e161. .......... .. 102/514 W0 WO 99/00468 1/1999 6374 743 Bl* 4/2002 H 6,439,125 , , Bl* 8/2002 6,973,879 Bl* FOREIGN PATENT DOCUMENTS DE 2839120 A * 9/1982 * cited by examiner 2/1983 * 8/1984 U.S. Patent May 1, 2007 Sheet 1 013 US 7,210,411 B2 U.S. Patent May 1, 2007 Sheet 2 013 US 7,210,411 B2 U.S. Patent May 1, 2007 Sheet 3 013 US 7,210,411 B2 US 7,210,411 B2 1 2 4.6 MM SMALL ARMS AMMUNITION Vickers Hardness. As a result, the bullet disclosed in US. Pat. No. 5,686,693 Will lack the desirable hardened target penetration capability. This application is the US national phase of international application PCT/GB2004/001111, ?led in English on 16 Mar. 2004, Which designated the US. PCT/GB2004/001111 claims priority to GB Application No. 03072725, ?led 27 It Would therefore be a considerable advantage if a Way could be found to utilise steel or other metal having a Vickers Hardness equal to at least 550 (using a 10 kg load) Mar. 2003. The entire contents of these applications are as the principal component of a small arms projectile, While incorporated herein by reference. enabling the projectile to be engraved by the ri?ing and not introducing unacceptable friction or Wear, and avoiding the expensive construction of applying a jacket to the projectile. BACKGROUND OF THE INVENTION 1. Field of the Invention SUMMARY OF THE INVENTION This invention relates to ammunition for use in a Weapon having a ri?ed barrel, and especially to an improved form of projectile for small arms ammunition. 2. Discussion of Prior Art When a projectile is ?red from a ri?ed barrel, the projec tile must deform as it travels along the barrel so that material According to the present invention there is provided the combination of a gun having a ri?ed barrel and a round of ammunition; the ri?ing of the barrel comprising ri?ing grooves Which are separated by lands extending helically along the length of the barrel; the round of ammunition comprising a projectile; the projectile having a body com prising a substantially cylindrical body, and at least one forming part of the projectile is forced into the spaces betWeen the lands forming the ri?ing. This process is called engraving, and causes a spin to be imparted to the projectile by virtue of the longitudinal tWist of the ri?ing. The deformation of the projectile, its travel along the barrel effectively as a force ?t to the ri?ing, the high linear acceleration imparted by the gun propellant on ?ring, and annular groove formed in and encircling the said substan tially cylindrical body; the projectile further being provided 25 the consequent high rate of angular acceleration and asso ciated force acting betWeen ri?ing and projectile all con tribute to substantial Wear on the barrel. If this Wear rate can be reduced, substantial bene?ts With a coating of copper or copper alloy; Wherein the body of the projectile is formed from a metal having a Vickers Hardness of not less than 550, and the coating is of a thickness not less than the depth of the said ri?ing grooves. Normally, the projectile Will also have an ogival nose portion of the body forWard of said forWard body portion, although other forms are possible. The body of the projectile should normally have a diam eter Which is not greater than that de?ned by the roots of the For this reason, loW friction, readily deformable materials grooves of the ri?ing. Upon engagement With the ri?ing the are normally selected for small arms bullets, for example body is thus engraved, so that the material of the projectile lead. In order to increase the overall density of the bullet, it 35 is deformed, and thus engages With the lands, inducing spin has also been proposed to use steel. HoWever, steel is not in the projectile due to the tWist of the ri?ing. This defor readily deformable, and causes unacceptable barrel Wear. On mation gives the body an, interference ?t With the ri?ing so the other hand, hardness is a very desirable characteristic for as also to provide effective obturation by restricting or the bullet material, in order to minimise nose tip ablation folloW, including increased barrel life, higher muZZle veloc ity and hence increased accuracy and lethality. 30 during penetration of hardened targets such as, for example, 40 titanium/kevlar body armour. For these purposes, a Vickers Hardness of at least 550 (using a 10 kg load) is the minimum desirable. In seeking to overcome these problems, it has been preventing the escape of propellant gases past the projectile via the ri?ing grooves. The length and precise diameter of the body should be designed With these factors in mind. Regard must also be taken to ensure that the force required to effect the engraving and to propel the projectile along the barrel is not excessive, and this is the reason Why the common practice to make a small arms bullet from a steel 45 diameter of the body should not normally be greater than core, enclosed in a gilding metal jacket. that of the ri?ing groove. This force is substantially reduced This latter solution is practical, but results in a bullet by the said at least one annular groove formed in and having a relatively expensive construction. This is a very encircling the body. signi?cant disadvantage since small arms ammunition is The depth of said at least one annular groove should consumed in large quantities, and the market for such 50 preferably be betWeen about 1% and 10% of the nominal ammunition is highly competitive. diameter of the projectile, and an optimum design may be In US. Pat. No. 5,686,693 there is disclosed a 7.62 mm betWeen 2% and 6%. bullet formed from a steel alloy, having a forWard body The material selected for the projectile body Will depend partly upon the function Which the projectile is to perform. lands of an associated gun, and a rearWard body portion 55 For a Warshot ammunition nature to be used in combat having a greater diameter, and provided With annular portion Whose diameter corresponds to that of the ri?ing of copper. In use, the copper coating acts as a lubricant, and conditions, steel is a suitable material, as it is inexpensive and can be readily formed into the desired shape, eg by a very much less than the desirable minimum value of 550 muZZle velocity. grooves. The body is provided With a coating Which can be cold-forming process. Tungsten is another possible material is less thick than the depth of the ri?ing. When ?red from the because hardness is an important characteristic for target 60 ri?ed barrel, the ri?ing therefore cuts through the copper defeat, as are alloys of tungsten, and tungsten carbide. coating so that the steel body of the bullet is engraved by the ri?ing. In the disclosure it is stressed that the steel of the The projectile is coated With copper or a copper alloy, Which is more readily deformable than the material of the body must be soft, so as to permit this engraving to occur Without undue barrel Wear. The maximum value for the projectile body itself, and Which may have a loWer coe?i hardness of the steel body mentioned in the disclosure is 210 65 cient of friction. These factors can lead to a reduced engrav ing force With correspondingly loWer barrel Wear and higher Brinell, Which equates to a Vickers Hardness of 213, ie US 7,210,411 B2 3 4 Acoating thickness between 0.07 mm and 0.3 mm may be When the body 9 and associated coating 13 passes from the gun chamber into the ri?ed part of the barrel, by virtue suitable. Such a coating could conveniently be applied by electroplating or by chemical deposition. A coating thickness greater than 0.1 mm may be desirable. Additionally, molybdenum disulphide may be applied as an outer coating, for example by a centrifugal deposition process. The invention is particularly but not exclusively appli cable to small arms Weapons systems, having a nominal calibre of 20 mm or less, especially 9 mm or less. BRIEF DESCRIPTION OF THE DRAWINGS The invention Will noW be described by Way of example only With reference to the accompanying draWings, of whichzi FIG. 1 shoWs, partially cut aWay, in elevation, a round of small arms ammunition incorporating a projectile for use in combination With a gun having a ri?ed barrel, in accordance of its greater diameter, the body becomes engraved by the ri?ing 17. The diameter of the body 9 and coating 13 should preferably be substantially equal to or less than the diameter of the ri?ing grooves 18, While the grooves 12 can have substantially the same diameter as the barrel diameter. The presence of the grooves 12 facilitates the necessary deformation of the coating 13, thus enabling the engraving to take place With a substantially reduced axial force. The fact that the coating 13 can deform into the grooves 12 contributes considerably to a dramatic reduction in the axial force required for engraving to occur. The coating 13 is of a malleable material Which can be copper or a copper alloy and could additionally comprise an outer layer of a loW-friction material such as molybdenum disulphide. This coating 13 is of a thickness greater than the depth of the ri?ing grooves, and is of a relatively softer material than that of the projectile 1, it can also engrave With the invention; 20 more readily, and thus contribute for this reason also to a FIG. 2 shoWs, in sectional elevation, to an enlarged scale, reduction in the engraving force required. Because the the projectile and a part of the cartridge case of the round coating is thicker than the depth of ri?ing, engraving can shoWn in FIG. 1; and take place entirely Within the coating so that the hard metal FIG. 3 shoWs, in sectional elevation, the projectile and of the projectile is kept substantially out of contact With the part of the cartridge case located in the chamber of a gun 25 material forming the ri?ing of the gun barrel. Therefore, having a ri?ed barrel and ready for ?ring. despite the hardness of the material forming the main part of the projectile body, barrel Wear from this factor is mini DETAILED DISCUSSION OF EMBODIMENTS mised. It Will be evident to the skilled addressee that all of these As shoWn in FIG. 1, a round of small arms ammunition 30 factors reducing the engraving force Will also result in comprises a projectile 1, and a brass cartridge case 2 assembled thereto. The rearWard portion 3 (FIG. 2) of the projectile is received Within the forWard part of the cartridge reduced barrel Wear, higher muZZle velocity, and hence increased lethality and accuracy. The projectile Which forms part of the combination of gun and ammunition tile according to the invention is also case, and the tWo components are held together by friction. The cartridge case contains a quantity of gun propellant 35 considerably less expensive to manufacture than a corre material 4, and a percussion primer cap 5 comprising an sponding conventional projectile in, for example, a gilding anvil 6, a quantity of primary propellant 7 and a closure cap metal jacket. 8 Which is received as a press ?t in a recess in the rear end The optimum design parameters for the projectile accord face of the cartridge case. ing to the invention can be determined by those skilled in the The projectile body is of elongate form and is cold formed 40 art, based on the teaching contained herein. from steel having a Vickers Hardness of at least 550 (using The invention is particularly but not exclusively appli a 10 kg load). It can subsequently be given a heat treatment cable to small arms ammunition. In one particular example, to provide the desired hardness or other physical properties. the invention has been successfully applied to 4.6 mm gun The projectile comprises a body portion 9 of substantially and ammunition. In a lodged bullet test, in Which the force cylindrical form. The projectile also has a nose portion 10 45 is measured Which is required to dislodge a bullet Which is forWard of the portion 9, the nose portion 10 having an stuck in the ri?ed section of a gun barrel, it has been found ogival forWard end 11. that a projectile made from steel having no reduced-diameter Because of the substantial hardness of the projectile body body portion 9 or suitable grooves into Which a coating 13 material, the projectile is highly effective at penetration of can readily deform, Would require an unacceptable axial targets such as titanium/kevlar body armour. Moreover, the 50 force, With associated unacceptably high rate of barrel Wear, hardness also serves to minimise ablation of the projectile and for this reason steel bullets, particularly those having tip pro?le, thus further contributing to its effectiveness in considerable hardness, have not been considered practical target penetration, as Well as stability in ?ight. hitherto. The body portion 9 comprises three parallel grooves 12 A 4.6 mm projectile as described With reference to FIGS. therein, Which encircle the projectile, and the surface of the 55 1 and 2, but Without the grooves 12 Was found to require an projectile is covered With a coating 13. unduly high axial force of the order of 6000 N; addition of As shoWn in FIG. 3, in use the round of ammunition comprising the assembled primed and ?lled cartridge case 2, together With the projectile 1 are ?red from a gun having a the grooves 12 reduced this force to 2000 N. The invention claimed is: 1. A projectile for a gun having a ri?ed barrel, said ri?ed barrel 14, in the conventional manner, ie by cham 60 projectile comprising a round of ammunition; the ri?ing of bering the round Within the gun chamber 15, and arranging the barrel comprising ri?ing grooves Which are separated by for the cap 5 to be struck by a ?ring pin. lands extending helically along the length of the barrel; the The projectile is thus propelled doWn the gun barrel. The projectile having a body comprising: diameter of the body 9 and coating 13 together is greater that a substantially cylindrical body, said body having a plu the diameter de?ned by the ri?ing lands 16 by an amount 65 rality of annular grooves formed therein; approximately half that of the deposited thickness of the a coating of copper or copper alloy substantially sur coating 13 over the body 9. rounding said body; Wherein the body of the projectile US 7,210,411 B2 6 5 is formed from a metal having a Vickers Hardness of not less than 550, and the coating is of a thickness not a coating of one of copper and copper alloy substantially less than the depth of the said ri?ing grooves, Wherein a portion of the coating is deformed into a portion of jectile is formed from a metal having a Vickers Hard ness of not less than 550, and the coating is of a said annular grooves. thickness betWeen 0.07 mm and 0.3 mm, and Wherein 2. A projectile according to claim 1 Wherein the projectile has an ogival nose portion of the body. 3. A projectile according to claim 1 Wherein the depth of said annular grooves is betWeen about 1% and 10% of the nominal diameter of the projectile. 4. A projectile according to claim 3 Wherein the depth of said annular grooves is betWeen about 2% and 6% of the nominal diameter of the projectile. 5. A projectile according to claim 1 Wherein the projectile body is made of a material selected from the group com prising steel, tungsten, alloys of tungsten, and tungsten surrounding said body, Wherein the body of the pro a portion of the coating is deformed into a portion of said annular grooves. 16. A projectile according to claim 15 Wherein the depth of said annular grooves is betWeen about 1% ad 10% of the nominal diameter of the projectile. 17. A projectile according to claim 15 Wherein the pro jectile body is made of a material selected from the group comprising steel, tungsten, alloys of tungsten, and tungsten carbide. 18. A projectile according to claim 15 Wherein the thick ness of the coating is greater than 0.01 mm. 19. A projectile according to claim 15 Wherein the pro jectile has an outer coating of a material Which has a loWer carbide. 6. A projectile according to claim 1 Wherein the thickness of the coating is betWeen 0.07 mm and 0.3 mm. coef?cient of friction than that of the projectile body. 7. A projectile according to claim 1 Wherein the thickness 20 20. A projectile according to claim 19 Wherein the said of the coating is greater than 0.1 mm. outer coating is of molybdenum disulphide. 8. A projectile according to claim 1 Wherein the projectile has an outer coating of a material Which has a loWer 21. A projectile according to claim 15 having nominal calibre of 9 mm or less. coef?cient of friction than that of the projectile body. 22. A projectile according to claim 21 Wherein the said 9. A projectile according to claim 8 Wherein the said outer 25 nominal calibre is 4.6 mm. coating is of molybdenum disulphide. 23. A projectile for a gun having a ri?ed barrel, the ri?ing 10. A projectile according to claim 1 Wherein the gun and of the barrel comprising ri?ing grooves Which are separated by lands extending helically along the length of the barrel, the projectile comprising: 11. A projectile according to claim 10 Wherein the said 30 a substantially cylindrical body portion, said body portion the round of ammunition have a nominal calibre of 20 mm or less. nominal calibre is 9 mm or less. 12. A projectile according to claim 11 Wherein the said nominal calibre is 4.6 mm. 13. A combination of gun and ammunition having a formed from a metal having a Vickers Hardness of not less than 550, an outer diameter of said body portion is less than an internal diameter of the barrel, said body portion including a plurality of annular grooves; and projectile according to claim 1 Wherein the diameter of the 35 body portion is less than or equal to the diameter de?ned by said lands. 14. A combination according to claim 13 Wherein the diameter of the body portion is substantially the same as the 40 diameter de?ned by said lands. a deformable coating comprised of one of copper and a 15. A projectile for use in combination With a ri?ed barrel 24. A projectile according to claim 23, Wherein said coating has a thickness greater than a depth of said ri?ing of a gun, the projectile having a body comprising: a substantially cylindrical body portion, a plurality of annular grooves formed in and encircling said body portion; copper alloy, said coating substantially surrounding said body portion; Wherein said deformable coating and said annular grooves comprise a means for deforming a portion of said coating into a portion of said annular grooves during ?ring of the projectile. grooves.