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Publication numberUS3400661 A
Publication typeGrant
Publication dateSep 10, 1968
Filing dateMay 13, 1966
Priority dateMay 13, 1966
Publication numberUS 3400661 A, US 3400661A, US-A-3400661, US3400661 A, US3400661A
InventorsCoon John M, Sturm Rolland G
Original AssigneeJohn M. Coon, Rolland G. Sturm
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
US 3400661 A
Abstract  available in
Previous page
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Claims  available in
Description  (OCR text may contain errors)

Sept. 10, 1968 J. M. COON ETAL PROJECTILE 2 Sheets-Sheet 1 Filed May 13, 1966 S R m m w i W W5 M z J o R Z W, am 7" 62 ATTORNEY PROJEGTILE Filed May 13, 1966 2 Sheets-Sheet 2 0 6 C. it, a;

INVENTORS ,Jo/m M C 0012 Rolland 65.1fm:

BY gm ATTORNEY United States Patent 3,400,661 PROJECTILE John M. Coon, Rte. 2, Petersburg, Tenn. 37144, and gollaznd G. Sturm, 1520 Forbes Drive, Huntsville, Ala.

Filed May 13, 1966, Ser. No. 550,050

Claims. (Cl. 10293) ABSTRACT OF THE DISCLOSURE A frangible sabot for a projectile comprising a generally cylindrical skirt closed at one end. The closed end defines a continuous surface with an external central concave portion and a toroidal portion concentric to and surrounding the concave portion. A plurality of spaced fingers extend generally parallel to the longitudinal axis of the skirt, beyond the closed end of the skirt and function to releasably hold a projectile against the concave portion of the skirt.

The concepts of the present invention are broadly applicable to any fire arm tubular member used to fire bullets such as shotguns, pistols, rifles, cannons, and other like types of guns, without regard to the manner in which the thrust is created. However, by way of example, the present invention is described and illustrated herein for use with a conventional smooth bore shotgun.

In general terms, the present invention includes a bullet which may be broadly defined as including a destructible sabot having mounted thereon a projectile of smaller size. The sabot is generally of a diameter substantially or nearly substantially the same as the internal bore diameter of the gun with which it is used and is constructed from a light-weight frangible material in such a manner as to engage and hold :a smaller projectile at one end. The construction is such that a bore constriction (commonly referred to as a choke) will cause the sabot to release the projectile as the bullet arrives at and enters the bore constriction.

More specifically, in that form of the invention shown by way of illustration, the sabot of the present invention is formed as a cylindrical body of external diameter substantially equal to that of a conventional bullet normally projected by the firearm; however, the sabot is of a frangible nature, which may be crushed or broken by transverse inward pressure caused by a diminishing of a bore of the gun as is the case when using a choke. At the front of the sabot, the body is provided with forwardly projecting fingers which receive and retain a projectile of less diameter than the minimum diameter of the diminished or constricted portion of the bore of the gun. The rear portion of the projectile becomes seated in a concave cup-like portion of the sabot body when the projectile is received and retained by the projecting fingers. With this arrangement and construction the sabot and projectile are initially thrust forward within the bore of a gun as a single unit.

As the single unit com-prising the sabot and projectile pass through the bore of a gun and immediately upon encountering the constricted portion of the bore the side walls of the sabot are initially deflected inward without causing fracture of the sabot. Simultaneously with the side wall deflection the projecting fingers on the front of the sabot body are caused to spread or open outwardly of the body thereby releasing the projectile. Instantaneous with the opening of the fingers of the sabot the projectile separates therefrom due to the fact that the sabot loses velocity as a result of drag on the periphery of the bore. The projectile, however, having been released almost instantaneously as the sabot encountered the constricted portion of the bore, maintains its initial full velocity and passes out of the gun at this velocity or higher depending upon the extent of the constriction and its effect on increasing the thrust velocity near the end of the bore. At the same time as the projectile continues its separate travel the sabot moves further into the constricted portion of the bore and fractures due to its frangible characteristic. The sabot passes out the end of the bore in a crushed and fractured condition.

It is important to note that the sabot has sufiicient flexibility to seal the bore of the gun against blow-by as it carries the projectile to the constricted area thereby assuring a maximum velocity from the thrust created. Moreover, since the combined weight of the projectile and sabot of the present invention is less than that of a conventional projectile which approximates the internal diameter of the gun bore the maximum velocity obtainable from a given degree of thrust is substantially increased over such conventional bullets.

The particular sabot construction of the present invention also provides the projectile with accuracy since it releases the projectile prior to fracturing and eliminates possible interference with the flight of the projectile.

From the foregoing it will be seen that it is an object of the present invention to provide a novel and improved sabot, or thrust-transmitting carrier which a projectile of a diameter less than the smallest diameter of the bore of the barrel through which it is projected can be effectively and efficiently projected with a greater velocity than that of a projectile fitting the barrel.

It is further an object of the present invention to provide a bullet including a sabot, or thrust transmitting carrier, formed of a frangible material which permits the separation of a projectile therefrom as the sabot is initially deformed by a barrel constriction but prior to fracture.

It is also an object of the present invention to provide a sabot for firearms including a means for the releasable retention of a projectile of smaller diameter than the barrel of the firearm through which it is to pass.

Another object of the present invention is to provide a novel sabot for :a bullet which is capable of releasing its projectile prior to reaching the end of a barrel through which it is to pass and immediately thereafter becomes fractured while still in the barrel.

Numerous other objects, features and advantages of the present invention will be apparent from consideration of the following specification taken in conjunction with the accompanying drawings, in which:

FIG. 1 'is an exploded view of the sabot and the projectile of the present invention;

FIG. 2 is a vertical sectional view of the sabot and projectile in assembled relation;

FIG. 3 is a fragmentary View, partly in section, illustrating a gun having a cartridge, sabot and projectile seated in the firing chamber thereof;

FIG. 4 is a fragmentary view of the muzzle end of the barrel and the choke of the gun illustrated in FIG. 3 wherein the projectile has just separated from the sabot prior to fracturing of the sabot;

FIG. 5 is a similar view to that of FIG. 4 but showing the sabot and projectile after further travel through the gun bore.

The sabot of the present invention is generally indicated by the numeral 10 in the drawings, and is here shown as substantially cylindrical. The upper, or forward, portion of the sabot 10 is continuous to completely close off that end of the sabot. This upper portion has a unique configuration which generally comprises a central concave cup-like portion 12, illustrated as generally spheroidal in shape for the corresponding spheroid J projectile, and a concentric toroidal shaped portion 13. A plurality of fingers 11 extend axially outward of upper portion of the sabot surrounding the central concave portion 12. Communicating with the outer edges of the toroidal portion 13 and extending axially downward therefrom is a cylindrical skirt 14 which substantially forms the body of the sabot and is of such a diameter as to fit closely adjacent the side walls of a gun bore.

As mentioned previously, the sabot of the present invention is made from a light-weight frangible material, that is, it possesses a very limited capability of flexing before fracturing and breaking apart but does not deform. Generally, it is preferred to use various plastic materials having limited elongation and low modules of elasticity. A specific material is polystyrene having less than 1% elongation. It should be understood, however, that any frangible material satisfying the concepts of the present invention may also be employed to form the sabot.

Next, in discussing further the structural aspects of the sabot, it is pointed out that the central concave portion 12 provides a seat within which a projectile is held on the sabot 10. As illustrated, the concave portion 12 is spheroid in shape since the projectile is a spheroid. It would appear that the particular shape could vary depending upon the particular configuration of the base of the projectile. However, any shape employed must ensure that it only functions as a seat for the projectile and does not serve to restrain the projectile from parting with the sabot.

Concentric of the concave portion 12 is the toroidal shaped portion 13 which continuously communicates with the skirt 14 along its outer edge and with the concave portion 12 along its inner edge. The transition from one portion to another is gradual so as to provide a smooth, continuous upper surface for the sabot interrupted only by the fingers 11.

The combined geometric constructions described above provide the sabot with good strength for its thrusttransmitting function. Moreover, it allows the frangible material of which the sabot is formed to flex slightly without fracturing. This slight flexing is utilized when the sabot and projectile are fired through a gun bore. The skirt 14 flexes to sealingly engage the side walls of the gun bore to prevent blow-by as the sabot and projectile move therethrough. Maximum velocity from a given powder charge is thus obtained. The upper, or forward, portion of the sabot also flexes when encountering the bore constriction or choke of the gun. The flexure which takes place on this portion is inward and serves to cause the fingers to release the projectile from the sabot prior to fracturing of the sabot. All of this will be more apparent from the description to follow.

The plurality of fingers 11 and preferably integrally formed with the sabot body and of the same frangible material. These fingers are arranged and located in such 1 a manner that they will lightly engage the peripheral surface of the projectile seated in the concave portion 12 and maintain it in place on the sabot. As specifically illustrated with the spheroid projectile, the fingers 11 extend somewhat beyond the maximum diameter of the projectile 15 and turn slightly inward toward the axis of the combined sabot and projectile. As a result, the fingers lightly engage the projectile and hold it in place.

It should be noted that at the base of the fingers there is a gap 9 between the continuous upper surface of the sabot and the fully seated projectile. When the sabot initially engages the constricted portion of the gun bore as it passes therethrough, the toroidal and concave portions 12 and 13 deflect slightly inward prior to fracture. This slight deflection causes the upper surface of the sabot in the area of the gap 9 to be pushed against the surface of the projectile thus eliminating the gap. However, this simultaneously causes the outward ends of fingers 11 to deflect away from the projectile in a separated or open manner. The projectile is then free to become separated from the sabot. As a result, the projectile is instantae neously separated from the sabot due to the sabot slowing down from drag against the gun bore. Of course, further movement of the separated sabot into the constricted gun bore causes complete fracturing of the sabot due to increased inward pressure.

As seen in FIG. 3, the sabot '10 having its projectile 15 seated in place is attached at the rear open end of the skirt to a powder-carrying cartridge 18. The powder may be charged to both the cartridge and the hollow interior 16 of the sabot.

Any gun with which the sabot and projectile of the present invention is to be used must have some means for causing the sabot to fracture at a predetermined point in the bore of the gun during the passage of the sabot therethrough. One convenient method to provide for the fracturing of the sabot is to use a conventional choke 20. Such chokes are well known in the art, and can reasonably perform their usual function of preventing the scattering of shot as well as the function of fracturing the sabot of the present invention. Suchfracturing should be understood as taking place only after the projectile has sep-.

arated from the sabot.

The gun here shown for discharging the projectile is a gun having a smooth-bore barrel indicated at 22.

It will now be understood that, in using the bullet of the present invention, the sabot 10 is provided with a projectile 15, and may be attached to a cartridge 18; or, some other source of a rapidly expanding gas may be provided, such as a capsule of compressed gas thereby creating a thrust at the rear of the sabot. When the gas is released, whether through the burning of a gun powder or through the release of a pressurized gas, the gas fills the hollow portion 16 of the sabot, both forcing the skirt 16 to flex against and sealingly engage the walls of the bore, and urging the sabot 10 toward the muzzle of the gun.

Although the projectile 15 is shown to be spherical, it will be seen that any other shape desired can be used with equal success, since the projectile does not have to conform to the gun bore.

At this point, it should he understood that it is especially desirable to have the total weight of the projectile 15 plus the sabot 10 less than the weight of a projectile that would normally be used in a gun of the same given caliber. With this arrangement, there is approximately the same force or thrust produced by the expanding gas but less total mass to be moved; hence, the maximum obtainable velocity of the sabot with the projectile according to the present invention Will-be greater than the velocity of a conventional projectile of increased size from a gun of a given caliber.

To illustrate the increased velocity obtainable with the bullet of the present invention, it is pointed out that a conventional 12-gauge shotgun slug weighing in the range of 400-500 grains will obtain a muzzle velocity of about 1500 to 1600 feet per second using factory loaded cartridges. A bullet according to the present invention comprising a ball projectile weighing approximately grains and a 0.730 inch diameter sabot weighing in the range of 2025 grains (l2-gauge size) using a moderate powder charge will have a muzzle velocity of about 3000-4000 feet per second imparted to the ball projectile.

It is important to note that, as shown in FIG. .4, the sabot does not meet any obstruction until it has reached the end of the barrel proper. After it has traveled through the full length of the barrel, the sabot and its projectile have attained their maximum velocity; and, at this time, the sabot engages the entrance of the choke, with its slightly diminished diameter and instantly the forward end of the sabot is slightly deflected inward to the extent that it causes fingers 11 to open, as previously described, and free the projectile 15. The sabot has not fractured at this moment but does begin to lose velocity due to drag on the side walls of the bore whereby the projectile separates therefrom while substantially maintaining its original velocity. At this point, the projectile is free of the sabot and will maintain the same course that it had when it left the sabot.

After projectile 15 has completely separated from the sabot further compressive forces on the frangible sabot cause it to fracture while it continues to pass through choke 20 and lose velocity.

As is shown in FIG. 5, the projectile is completely free of the choke before the sabot is completely broken up; but, it is important that the sabot, urged forward by the remaining gas pressure, will be further broken by the further decrease in diameter of the choke, and will be sufficiently fractured to be blown free of the barrel and choke of the gun.

It is also pointed out that substantially no accuracy of the projectile will be lost since the projectile completely separates from the sabot prior to the sabot fracturing and breaking up. The release of the projectile should not interfere with its path of flight.

Although the gases within the bore of the gun may be somewhat restricted at the time the sabot is detained by the choke, it should be realized that the projectile, by this time, has attained its maximum velocity, and could benefit very little by the pressure that may otherwise be exerted on the projectile during its travel through the choke.

It will thus be seen that the bullet of the present invention provides a means by which the muzzle velocity of a projectile can be substantially increased, but without loss of efiiciency due to the escaping of gas around the projectile. The sabot skirt provides an effective seal, having sufficient elasticity, despite its frangible nature, to expand and seal the bore with the gasses as the bullet is propelled forward. The projectile is released from the sabot only after the sabot and projectile have attained their maximum velocity and prior to fracture of the sabot and, the sabot is subsequently blown clear of the bore so that no cleaning or the like is required after firing one round.

It will, of course, be understood that the particular embodiment of the present invention here shown is by way of illustration only, and is meant to be in no way restrictive; therefore, numerous changes and modifications may be made, and the full use of equivalents resorted to without departing from the spirit or scope of the invention as defined by the appended claims.

We claim:

1. A frangible sabot for a projectile comprising a generally cylindrical skirt closed at one end, said closed end including a plurality of spaced fingers extending generally parallel to the longitudinal axis of said skirt beyond said closed end for releasably holding a projectile against said closed end, said cylindrical skirt and said closed end being sufficiently fractionable that they will be crushed as the sabot travels down a barrel of a gun so that said fingers will release said projectile.

2. A frangible sabot according to claim 1 wherein the closed end comprises a continuous surface defined by a central concave portion and a toroidal portion concentric to the concave portion.

3. A frangible sabot according to claim 2 wherein the central concave portion is adapted to receive and seat the base of a projectile.

4. A frangible sabot according to claim 3 wherein the fingers extend outward in a normal position for holding a projectile seated in the concave portion when the closed end of the sabot is in a normal undefiected relationship.

5. A frangible sabot according to claim 4 wherein the fingers extend outward in an open position for releasing a projectile seated in the concave portion when the closed end of the sabot is in an inwardly deflected relationship.

6. A bullet comprising a cylindrical frangible sabot having one end closed, said closed end comprising a continuous surface defined by a central concave portion and a toroidal portion concentric to the concave portion, a projectile seated in said concave portion, and a plurality of fingers extending outward from the continuous surface of the closed end and surrounding the concave portion for releasably engaging and holding the projectile in place.

7. A bullet according to claim 6 wherein the fingers are so constructed as to leave a gap between the projectile and the continuous surface of the closed end adjacent the fingers wherein there is no engagement between the sabot and the projectile.

8. A method of propelling a projectile from a tubular member comprising the steps of releasably holding said projectile on the forward end of a sabot, placing the combined sabot and projectile in the tubular member, creating a thrust behind the sabot thereby propelling the combined sabot and projectile through the tubular member, releasing and separating the projectile from the sabot when the combined sabot and projectile substantially achieves its maximum velocity and while both the sabot and projectile are still in the tubular member, and ejecting the unrestrained projectile from the tubular member at substantially its maximum achieved velocity.

9. A method according to claim 8 wherein the projectile is released and separated from the sabot by inwardly deflecting without fracturing the forward end of the sabot while exerting a drag force on the sabot.

10. A method according to claim 9 including the additional step of fracturing the sabot after the projectile has been released and separated but while the sabot is still in the tubular member and ejecting the fractured sabot from the tubular member subsequent to the ejection of the projectile.

References Cited UNITED STATES PATENTS 43,017 6/1864 Ganster 102-93 1,309,791 7/1919 Aasen 102-93 X 2,820,412 1/1958 Beeuwkes et a1. 102-93 3,055,268 9/1962 Rosenthal 102-93 X 3,148,472 9/1964 Hegge et a1. 102-93 X 3,164,092 1/1965 Reed et al 102-93 3,185,094 5/1965 Zehfeld 102-38 ROBERT F. STAHL, Primary Examiner.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US43017 *Jun 7, 1864 Improvement in attaching sabots to spherical projectiles for ordnance
US1309791 *Dec 8, 1917Jul 15, 1919 Planograph
US2820412 *Oct 20, 1948Jan 21, 1958Beeuwkes Jr ReinierProjectile for firearms
US3055268 *Dec 8, 1960Sep 25, 1962Henry RosenthalDiscarding obturator and rotator for projectiles
US3148472 *Jun 11, 1962Sep 15, 1964Edward N HeggeSubcaliber projectile and sabot for high velocity firearms
US3164092 *Nov 13, 1962Jan 5, 1965Remington Arms Co IncAmmunition sabot
US3185094 *Jun 10, 1963May 25, 1965Rheinmetall GmbhCartridge case extension piece for use with projectiles
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US3601061 *Jan 30, 1969Aug 24, 1971Trw IncAmmunition for high firing rate, light gas hypervelocity gun
US3795172 *Sep 5, 1972Mar 5, 1974Us NavyApparatus for rapidly accelerating and cushionably decelerating a piston-like member
US4126955 *Mar 17, 1977Nov 28, 1978The United States Of America As Represented By The Secretary Of The ArmyHigh velocity tapered bore gun and ammunition
US5150909 *Apr 4, 1991Sep 29, 1992Edwin FitzwaterAir gun pellet design
US5452535 *Jun 4, 1993Sep 26, 1995Impromark, Inc.Shotgun shell wad/shot cup retarding device
US6128846 *Jun 8, 1998Oct 10, 2000Inpromark, Inc.Length shotgun choke tube
US6192612 *Jan 22, 1999Feb 27, 2001Oblon, Spivak, Mcclelland, Maier & Neustadt, P.C.Propulsion device
US7987790Aug 2, 2011Scarr Kimball RRing airfoil glider expendable cartridge and glider launching method
US8065961 *Dec 23, 2008Nov 29, 2011Kimball Rustin ScarrLess lethal ammunition
US8327768Jul 22, 2011Dec 11, 2012Kimball Rustin ScarrRing airfoil glider expendable cartridge and glider launching method
US8511232Jun 10, 2011Aug 20, 2013Kimball Rustin ScarrMultifire less lethal munitions
US8528481 *Nov 23, 2011Sep 10, 2013Kimball Rustin ScarrLess lethal ammunition
US8661983Jul 28, 2008Mar 4, 2014Kimball Rustin ScarrRing airfoil glider with augmented stability
U.S. Classification102/522, 89/14.6
International ClassificationF41A21/46, F42B14/00, F42B14/06, F41A21/00
Cooperative ClassificationF42B14/06, F41A21/46
European ClassificationF42B14/06, F41A21/46