Sub-calibre projectile of the fin-stabilised type incorporating a sabot and a penetrator

1. A sub-caliber projectile of the fin-stabilized type having a sabot and a penetrator linked together by means for shape matching, said means for shape matching incorporating a first profile machined at a bore of said sabot and cooperating with a second profile on said penetrator, each of said first and second profiles having a shape according to a section in an axial plane that alternates teeth and grooves, wherein the grooves in the sabot define housings for said teeth of said penetrator, wherein said means for shape matching include a front part, a median zone and a rear part, wherein, at a mean temperature there is axial play between one of said teeth of said penetrator and one of said housings which play is variable along a longitudinal axis of the projectile, in said front part and in said rear part, and the axial play increases from said median zone of said sabot toward both a front end between and a rear end of the sabot.

2. A sub-caliber projectile according to claim 1 , wherein in said median zone the play is substantially constant.

3. A sub-caliber projectile according to claim 2 , wherein said median zone extends longitudinally in the axial direction of the sabot at a push plate of said sabot.

4. A sub-caliber projectile according to claim 2 , wherein the median zone is of a length that is less than or equal to 30% of the full length of an interface between the sabot and the penetrator.

5. A sub-caliber projectile according to claim 2 , wherein said teeth and said grooves of said penetrator are of a constant width along said penetrator, wherein the teeth and grooves of the sabot are of constant length along said median zone, wherein the teeth and grooves of the sabot are of variable lengths along the front part and along the rear part.

6. A sub-caliber projectile according to claim 1 , wherein said profiles comprise threading on the penetrator cooperating with internal threading on the sabot.

7. A sub-caliber projectile according to claim 6 , wherein the width of the internal threads increases progressively between said median zone and said front and rear ends of said internal threading.

8. A sub-caliber projectile according to claim 7 , wherein the variations of the threads are defined such that at said mean temperature the plays are equally distributed on either side of each of said penetrator teeth, each of said penetrator teeth being substantially centered in each of said housings defined by said internal threading.

9. A sub-caliber projectile according to claim 2 , wherein the median zone extends longitudinally in the axial direction of the sabot at a push plate of said sabot.

10. A sabot for incorporating into a projectile according to claim 1 and incorporating a profile machined at a bore, such profile having a shape in a section along an axial plane that alternates teeth and grooves and is for cooperating with a matching profile on the penetrator, and the sabot, whose machined profile incorporates a median zone (M) at which the teeth and grooves are of a constant width, and front (F) and rear (R) parts at which the widths of the teeth and grooves are variable, the width of the grooves first increasing between the median zone (M) of the sabot and the front end of the sabot, and second increasing between the median zone (M) of the sabot and the rear end of the sabot.

11. A sabot according to claim 9 , wherein the median zone is positioned longitudinally at a push plate of said sabot.

12. A sabot according to claim 10 , wherein the median zone is of a length that is less than or equal to 30% of the full length of the machined profile.