Projectile body and corresponding ammunition round for small arms or a light firearm

Abstract

A projectile (14) for an ammunition round (10) for use with a small arms or light firearm comprises an elongated projectile body (16). The projectile body (16) has first and second axially opposed ends (18, 20) respectively and a cavity (20) extending there between. The cavity is able to hold a quantity of propellant (24). A plurality of seals (26) extend about an outer surface of the body (16). The seals (26) protrude radially from the body (16) and operate to form a substantial seal against an inner circumferential surface of a barrel (12) of the firearm. Two of the seals (26b and 26c) are mutually adjacent and spaced apart in a direction of a longitudinal axis of the body to form a seal bound outer surface portion (36) of the body (16). One or more holes (38) are formed in the body (16) enabling fluid communication between the cavity (22) and the seal bound outer surface portion (36) of the body (16). This enables pressure equalization inside and outside of the cavity (22) about the seal bound outer surface portion (36) when the projectile (14) is travelling through the barrel (12).

The invention claimed is: 
     
       1. A projectile body for an An ammunition round for small arms or light firearm, the projectile body being elongated and firearms having a barrel for firing the ammunition round comprising:
 a projectile body having: first and second axially opposed ends and a cavity extending between the first end and the second end, the first end being a leading end of the projectile and closed,; 
 a quantity of propellant held in the cavity being capable of holding a quantity of propellant for propelling the projectile body through the barrel; 
 a plurality of seals extending about an outer surface of the body, the seals being located rearward of the first end and forward of the second end, each seal protruding radially from the body to form a substantial seal against an inner circumferential surface of the barrel of a firearm, wherein two a first and a second of the plurality of seals are mutually adjacent and spaced apart in a direction of a longitudinal axis of the body to form a seal bound outer surface portion of the body; and 
 one or more holes formed in the body enabling fluid communication between the cavity and the seal bound outer surface portion of the body; 
 a boat tail portion located between an end of the seal bound outer surface portion of the body and the second end, the boat tail being tapered to reduce in outer diameter toward the second end and wherein the boat tail terminates at the second end and the cavity extends through the boat tail; and 
 a tubular case sealed at one end by a base, the case fitted over a portion of the projectile body, and wherein a portion of the case extending across the seal bound outer surface portion is provided with a constant inner diameter; and where a spacing L between outer most points of two axially most spaced apart seals satisfies the relationship L≥D, where D is the diameter of the maximum of diameter of the projectile body. 
 
     
     
       2. The projectile body ammunition round according to  claim 1  comprising a plurality of holes wherein the holes are spaced about the longitudinal axis of the body. 
     
     
       3. The projectile body ammunition round according to  claim 1  wherein each of the one or more holes has an outer opening on the seal bound outer surface portion and an inner opening that opens into the cavity and wherein for at least one of the holes the outer opening of that hole is closer to the first end than the inner opening of that hole. 
     
     
       4. The projectile body ammunition round according to  claim 1  wherein, when the cavity holds the propellant comprising comprises a plurality of grains of a solid propellant and each hole is arranged to have a diameter at least at one point between the cavity and the seal bound outer surface portion that is no greater than about three times an average grain size of the propellant. 
     
     
       5. The projectile body ammunition round according to  claim 1  wherein the one or holes are provided with temporary sealing devices. 
     
     
       6. The projectile body ammunition round according to  claim 5  wherein the temporary sealing devices comprise one of (a) a frangible seal, (b) a seal arranged to eject from the holes, or (c) a seal arranged to melt or combust; all by action of deflagration of propellant held in the cavity. 
     
     
       7. The projectile body according to  claim 1  comprising a boat tail portion located between an end of the seal bound outer surface portion of the body and the second end. 
     
     
       8. The projectile body ammunition round according to  claim 1  wherein, the first end terminates with a planar surface perpendicular to the longitudinal axis. 
     
     
       9. The projectile body ammunition round according to  claim 1  wherein, the first end terminates in a point being coaxial with the longitudinal axis. 
     
     
       10. The projectile body ammunition round according to  claim 1  comprising, a ballistic soft tip coupled with the first end of the body. 
     
     
       11. The projectile body ammunition round according to  claim 1 , wherein the cavity is a single cavity for holding the propellant and has a longitudinal center line co-axial with a longitudinal axis of the body. 
     
     
       12. The projectile body ammunition round according to  claim 1  comprising a sleeve disposed in the cavity and wherein the one or more holes extend through the sleeve into the cavity, wherein propellant for propelling the projectile body is held in the sleeve. 
     
     
       13. The projectile body according to  claim 1  wherein a spacing L between outer most points of two axially most spaced apart seals satisfies the relationship L≥D, where D is the diameter of the maximum of diameter of the projectile body. 
     
     
       14. An ammunition round comprising:
 a projectile body having first and second axially opposed ends and a cavity extending between the first end and the second end, the first end being a leading end of the projectile and closed, the cavity being capable of holding a quantity of propellant for propelling the projectile body;   a plurality of seals extending about an outer surface of the body, each seal protruding radially from the body to form a substantial seal against an inner circumferential surface of the barrel of a firearm, wherein two of the plurality of seals are mutually adjacent and spaced apart in a direction of a longitudinal axis of the body to form a seal bound outer surface portion of the body; and   one or more holes formed in the body enabling fluid communication between the cavity and the seal bound outer surface portion of the body;   a quantity of propellant held in the cavity;   a base seal closing the second end to confine the propellant in the cavity; and, a primer supported in the base seal.   
     
     
       15. An ammunition round for small arms or light firearms having a barrel for firing the ammunition round comprising:
 a projectile body having first and second axially opposed ends and a cavity extending between the first end and the second end, the first end being a leading end of the projectile and closed, the cavity being capable of holding a quantity of propellant for propelling the projectile body; 
 a plurality of seals extending about an outer surface of the body, each seal protruding radially from the body to form a substantial seal against an inner circumferential surface of the barrel of a firearm, wherein two a first and a second of the plurality of seals are mutually adjacent and spaced apart in a direction of a longitudinal axis of the body to form a seal bound outer surface portion of the body, wherein the first seal is closer to the first end than the second seal, a forward portion of the projectile body extends between the first seal and the first end, and a rearward portion of the projectile body extends between the second seal and the second end; and 
 one or more holes formed in the body enabling fluid communication between the cavity and the seal bound outer surface portion of the body; 
 a tubular case sealed at one end by a base, the case fitted over a portion of the projectile body with the base facing the second end of the projectile body and closing the cavity, wherein the case and the projectile body are relatively dimensioned so that every seal on the projectile lies outside of the case; and 
 a quantity of propellant retained within the cavity by the case, and wherein the first end of the projectile body protrudes from the case. 
 
     
     
       16. The ammunition round according to  claim 15  wherein the case and the projectile body are relatively dimensioned so that the case at least partially overlies at least one seal on the projectile body. 
     
     
       17. The ammunition round according to  claim 15  wherein the case and the projectile body are relatively dimensioned so that every seal on the projectile lies outside of the case. 
     
     
       18. The ammunition round according to  claim 15  wherein the quantity of propellant is such that substantially the entire cavity is filled with the propellant. 
     
     
       19. The ammunition round according to  claim 15  wherein the projectile and the case are relatively dimensioned such that a space is formed between the second end of the projectile body and the base of the case and wherein the propellant is retained between an inner surface of the cavity and the base of the case. 
     
     
       20. The ammunition round according to  claim 19  wherein the propellant is provided in a volume greater than that of the space so that at least a proportion of the propellant is held in the cavity. 
     
     
       21. The ammunition round according to  claim 19  wherein the propellant is provided in a volume to substantially fill the space and the cavity. 
     
     
       22. The ammunition round according to claim 1 wherein the plurality of seals includes a third seal located between the second seal and the second end. 
     
     
       23. The ammunition round according to claim 15 wherein the case has a constant inner diameter between the seal bound outer surface portion of the body. 
     
     
       24. The ammunition round according to claim 1 wherein the plurality of seals are arranged to form two seal bound outer surface portions of the body, and wherein the one or more holes formed in the body are arranged to enable fluid communication between the cavity and each of the two seal bound outer surface portions of the body. 
     
     
       25. The ammunition round according to claim 1 wherein the case has a circumferential wall that, for a portion adjacent the base, increases in thickness by way of a reduction of its internal diameter in the direction from a front end of the case toward the base to accommodate the boat tail so as to maintain a relatively constant spacing between the outer surface of the body and the internal diameter of the case. 
     
     
       26. A projectile body for small arms or light firearms having a barrel for firing the projectile, the projectile comprising:
 a projectile body having: first and second axially opposed ends and a cavity extending between the first end and the second end, the first end being a leading end of the projectile and closed;   the cavity capable of holding a volume of propellant for propelling the projectile body through the barrel;   a plurality of seals extending about an outer surface of the body, the seals being located rearward of the first end and forward the second end, each seal protruding radially from the body to form a substantial seal against an inner circumferential surface of the barrel, wherein a first and a second of the plurality of seals are mutually adjacent and spaced apart in a direction of a longitudinal axis of the body to form a seal bound outer surface portion of the body;   one or more holes formed in the body enabling fluid communication between the cavity and the seal bound outer surface portion of the body, the holes arranged to remain open after the projectile body is ejected from the barrel; and   a boat tail portion located between an end of the seal bound outer surface portion of the body and the second end, the boat tail being tapered to reduce in outer diameter toward the second end and wherein the boat tail terminates at the second end and the cavity extends through the boat tail.   
     
     
       27. The projectile body according to claim 26 wherein the projectile body has a length from the first end to the second end, and wherein the length of the projectile body is constant while the projectile travels through the barrel and in the air from the barrel to a target. 
     
     
       28. The projectile body according to claim 26 wherein the projectile body does not include a sleeve or tubular portion that is able to move relative to the holes after the projectile is ejected from the barrel.