US 2638051 A
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May 12, 1953 c. CRITCHFIELD SUB'CALIBER PRQJECTILE Filed Jan. 18, 1944 INVENTOR CHARLES L. ORITGHF/ELD .eww
Patented May 12, 1953 Charles L. Gritchfield, Chevy Chase, Md., assignor to the United States of America a represented by the Secretary 'of the Navy "Application January 18, 1944, SerialNo. 518,753
This invention relates to projectiles for guns and more particularly to sub-caliber projectiles adapted to attain high velocities when fired from a gun.
One object of my invention is the provision of a projectile for guns, which includesa subcaliber core and. adetachable sabot. The projectile is light in weight as compared with ordinary standard projectiles and presents a substantially full caliber rear surface to pressures developed in-the-gun barrel, the new projectile being capable of attaining a higher velocity in the barrel and maintaining that velocity throughout reasonable distances of fiight with maximum stability.
Another object of my invention is to provide a sub-caliber projectile having a sabot which is readily discarded during flight with minimum tendency of the core to yaw or deviate from the accurate course of travel, and without decreasing the velocity of the projectile. q,
Another object of my invention is to provide a projectile having a sub-caliber core and having distendable centering means "to ensure a snug well centered fit of the projectile during its travel through the gun bore.
A further object of my invention is to provide a projectile as described above which is simple to manufacture and is adapted to largequantity production.
These and other objects of the invention will be apparent from the following specification and the accompanying drawing, in which Fig. 1 is a side elevation of a preferred form of projectile made in accordance with my invention; Fig. 2 is a longitudinal cross-sectional view taken on line 22 of Fig. 1; and Fig. 3 is a front elevation of the projectile.
As conducive to a clearer understanding of certain features of my invention, it may be noted at this point that projectiles including sub-caliber cores and sabots for making the cores suitable for full caliber use have a number of advantages which ordinary standard projectiles do not possess. Projectiles having sub-caliber cores are lighter in weight than standard projectiles of equivalent caliber and may be fired from rifled, standard guns so as to take full efiect of pressures developed in the gun. The projectiles leave the gun at very high muzzle velocity and have potentially high striking power. Where the sabot releases from the projectile core during flight, the negative accelerating efiect of the atmosphere is considerably reduced and higher striking velocities are made possible.
- 1 Claim. (Cl. 102-93) Despite the many recognized advantages of P jectiles having sub-caliber cores, the projectiles are not widely used; one reason being that heretofore they have not been reliably stable in flight before the release of the sabot. One cause of this is due to poor axial centeringof the projectiles as they move through the gun tube, causing the projectiles totend to overturn or deviate in flight after leaving the gun.
A variety of materials and designs have been proposed in sabot-construction involving especially the use of reinforced plastics, aluminum alloys and tubular steel. In these constructions the sub-caliber projectile is centered in the sabot which in turn is to be centered in the bore of the gun, and this composite structure thus requires more care in attaining a properly centered projectile. .In addition to the disadvantage of a larger number of critical tolerances, previous sabots compared less favorably with standard ammunition because the sabot often yielded farther under transverse stresses than a steel projectile, and because the sabot was usually, though not necessarily, shorter than standard ammunition. The less certain centering of the sabot projectile combined with its inherently lower stability caused it to show larger yaw anddispersion than full caliber projectiles in the same gun.
Anotherdiificulty encountered is that of obtaining release of the sabot soon after the projectile leaves the gun muzzle. In this connection, some of the heretofore known sabots have failed to release with the result that the entire purpose of the projectile is defeated. In other cases, certain sabots in releasing upset the equi iibrium of the core.
A projectile made in accordance with the present invention has a sub-caliber core and substantially full caliber sabot means making the core suitable for firing from a rifled gun at high velocities. The projectile is well centered during travel through the gun barrel as well as stable in flight up to and after the time of discard of the sabot, which takes place promptly upon the projectiles leaving the gun bore in order to minimize the retarding efiect of the atmosphere without upsetting stability of the core.
Referring now more particularly to the practice of my invention, I find that a projectile assembly having a sub-caliber core and substantially full caliber discardable sabot means is efiectively stabilized in a rifled gun and in flight, through the inclusion of distendable centering means as a part of the projectile for insuring 3 snug, well-centered fit of the projectile during travel through the gun barrel. In this connection, I prefer to employ a distenda-ble ring or rings, made for example of plastic material, mounted about the main body of the projectile, preferably around a reduced diameter section of the sabot, and adapted to expand to a position of snug contact with: the. lands of the gum The sabot means. employed is released by. ail: pres-- sure and centrifugal force shortly after leaving the gun.
In the drawing, the projectile includes an elongated, cylindrical sabot [0 having an axial bore ll into which a sub-caliber core. [=2 smiglyfits, as by force fit or by threading. Thesabotincludes an elongated, axially-bored cylindrical; sleeve or skirt 13 of substantially full. caliber. diameter disposed tightly around the side walls of the core, leaving the ogive portion 121: oi the core protruding therefrom in a forward direction. The skirt I3 is made. of. light mataial, for example, plastic having.alaminatedfibrousfillen. and preferably includes zones oi weakness, such as symmetrically spaced radial cuts. L4.- extending. from the forward edge: wellto the rear of the. skirt. body for insuring ready release oi the entire sabot by. centrifugal. force during flight. oi the. projectile. The sabot. preferably mohidesat the rear of the skirtportiona. substantially full caliber base plug 15 which.- is made. for example, of Duralumin and. has a forwardly protruding portion IS. of. reduced. diameter secured as bypresafitor by threading, inthe. bore. of the skirt I3. The. base. plug [5i carries a. rotating band l1 made, for example,. of copper.
A ring. l8, preferably made of. plastic, is seated. around the forward end of. sabot. Hi to act as a slidable. bourrelet. The surface. of the bourrelet. and the. outer surface. of. the. forward end portion. of the skirt l3 form the. surface of a cone. having substantially the. same. axis as. the. skirt. bore. Hie. conical surface on.the. skirt terminates. at. its. rear. or enlarged end in a. shoulder l5. which serves to. stop sliding. move.- ment. of 'the bourrelet. during. acceleration in the gun.
When. the. projectile is. fired from a. gun. the slidable. bourrelet I 9; moves back, infliiencedby setback due to axial acceleration of the pro.- jectile. 'Ilhe bountelet expands. on the conical surface of the skintluntil' the shoulder. is. of the skirt is engaged; thus compensating for radial. clearance or. compressibility of the sabot,. and efiecting positive centering of the proiectile in the gun. Shortly after. theproiectile leaves the gun, the bourrelet. l8. and sabot [0. are discarded. under the action of centrifugal force; the hourrelet breaking readily, and the zones of weakness or cuts 14 in the skirt l3 aiding in ready discard of the sabot, including the skirt and the base plug 15. The projectile core moves ac curately, is quite stable in flight, and possesses high striking power throughout prolonged distances of travel.
Itwillibe. understood. that invention may used; to: goodadvantage; in. connection with projectile cores and sabots of widely difiering caliber. One type of projectile employed included an eleven millimeter core made of machinableallby tungsten. A twenty millimeter sahot. a plastic skirt, a Duralumin bore and; a. copper rotating band, was fitted amundr fire; core. A slidable plastic bourreletwas disposed around the Outer forward of thesabot. The projectile, when fired from; a: gun, exhibited excellent ballistic proper ties.
The projectile of my invention is simple to assemble and possesses. highly favorable ballistic properties. including stability; rapidity of flight and high potential striking power.
Although I have described one embodiment of the invention it is' obvious that many possible modifications of theinvention may be made, and it will. be understood that: the matter described and; herein to be interpreted as illustrative and not in 2; sense.
I claim? A nrvi tile. comprising a suhcaliber core, a base piug' backing the core. andhaving a forwa-rdly protruding portion the same in. diameter as the core", a; rotating band of channel crosssection fitted on the base plug, and a cylindrical sleeve tightly on the core, overlapping the forwardly protruding; portion and abuttingone of therflanges' of the rotating band.
References Cite inthe file of this patent UNITED SIATES PAmTS