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Publication numberUS3877374 A
Publication typeGrant
Publication dateApr 15, 1975
Filing dateJul 12, 1973
Priority dateJul 12, 1973
Publication numberUS 3877374 A, US 3877374A, US-A-3877374, US3877374 A, US3877374A
InventorsRalph L Cook
Original AssigneeOlin Corp
Export CitationBiBTeX, EndNote, RefMan
External Links: USPTO, USPTO Assignment, Espacenet
Protective coating for caseless ammunition
US 3877374 A
The propellant charge of a round of caseless ammunition is provided with a one or more layer coating of microcapsules containing silicone oil or the like to reduce transfer of external heat to the propellant.
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Description  (OCR text may contain errors)

United States Patent 1191 Cook [ PROTECTIVE COATING FOR CASELESS AMMUNITION [75] Inventor: Ralph L. Cook, Tallahassee, Fla.

[73] Assignee: Olin Corporation, New Haven,


[22] Filed: July 12, 1973 21 Appl. No.: 378,736

[ 52] US. Cl. 102/387 l02/D1G. 1', l02/D1G. 8 [51] Int. Cl. F42b 5/02 [58] Field of Search 102/103, 100, 101, 99,

102/D1G. 8, DIG. 1, 38

[56] References Cited UNITED STATES PATENTS 1,187,779 6/1916 Patten 102/010. 8 1,865,157 6/1932 Woodford 2,800,457 7/1957 Green et al. 106/132 X Apr. 15, 1975 Primary ExaminerBenjamin A. Borchelt Assistant Examiner-H. .1. Tudor Attorney, Agent, or FirmDonald R. Motsko; William W. Jones [5 7] ABSTRACT The propellant charge of a round of caseless ammunition is provided with a one or more layer coating of microcapsules containing silicone oil or the like to reduce transfer of external heat to the propellant.

6 Claims, No Drawings PROTECTIVE COATING FOR CASELESS AMMUNITION This invention relates to the coating of the propellant charge portion of a round of caseless ammunition to iinder external heat transfer to the propellant.

The concept of using caseless ammunition in con- ;unction with firearms is an old and very desirable one from a cost standpoint. Caseless ammunition. by elimidating the metal, plastic. or paper cartridge casing. is less expensive to manufacture. and does away with bothersome expended casings and the need to extract them from the firearm.

Caseless ammunition. however. by eliminating the casing. also presents problems relating to handling, moisture absorbtion. durability. and safety. The problem of safety relates to the possible premature ignition of the round when exposed to external heat either in the firing chamber. magazine. or even outside of the firearm.

Attempts have been made to solve the premature ignition problem by providing a protective coating for the propellant charge. Such solutions will be found in US. Pat. Nos. 3.212.440. issued Oct. 19. 1965 to J. B. Quinlan et al. disclosing a spray coating of methyl methacrylate and molybdenum disulfide or graphite; 3.397.637. issued Aug. 20. 1968 to J. Bobinski et al. disclosing a protective film of a cellulose derivative; 3.703.868. issued Nov. 28. 1972 to E. C. Braak. disclosing a polyolefine film protective coating: and 3.730.094. issued May 1. 1973 to J. B. Quinlan. disclosing a heat resistant explosive coating. The prior art solutions noted above have proven to possess unsatisfactory side effects. however. relating to unburned residue of the protective coating which residue remains in the firing chamber and gun barrel. and undesirable alter ation of ballistic performance.

This invention relates to a thermally protective coating for the external surfaces of caseless ammunition propellant charges. which coating has as its major constituent a vaporizable material. such as silicone oil. wax. or the like. the material being microencapsulated in a skin of gelatin. polyvinyl alcohol. epoxy. or the like. The microcapsules can be applied to the propellant in a plurality of layers so that the overall weight of the coating is reduced. and interstitial air within the layers acts as a further heat transfer barrier. The individual capsules should be in very fine granular form having a diameter in the range of about 5 1.000 microns. The individual microcapsule would consist of a major portion of encapsulated material and a minor portion of encapsulating skin. The encapsulated material should exhibit poor heat transfer characteristics. and should. under the heat developed when the round of ammunition is fired. vaporize so as to leave little or no residue behind in the firing chamber and barrel. By using a low heat transfer material which vaporizes upon firing. additional protection is given to the barrel against wear imparted thereto by the hot. corrosive combustion gases as the vaporized material passes through the barrel. If. during handling. the round is subjected to external heat. the encapsulating skin may rupture. however. this will merely expose the encapsulated material under conditions where it is free to flow to provide a continuous barrier to further heat transfer.

It will be noted that in acoating such as is proposed. of the three constituents. namely. encapsulated material.

the encapsulating skin. and air. only the encapsulating skin is a potential residue-producing agent. For any thickness coating, however. the skin is present only in very small percentages and thus any residue possible therefrom will be present in very minor amounts as compared to a solid coating. Further. the encapsulating skin can. if desired. be made of a material such as gelatin or polyvinyl alcohol which will vaporize when subjected to heat generated when the cartridge is fired. thus leaving no residue behind.

Silicone oil-fired microcapsules suitable for use with this invention can be made generally in accordance with the teachings of U.S. Pat. Nos. 2.800.457. issued July 23. l957 to B. K. Green et al.. or 2.800.458, issued July 23. 1957 to B. K. Green. The microcapsules may be applied to the propellant charge with a suitable adhesive which is compatable with nitrocellulose and the encapsulating skin on the microcapsules. An acrylic resinous adhesive may be used for this purpose. The adhesive may be self curing or may cure at a relatively low temperature. Alternatively. the adhesive may be set by removal of a solvent or carrying agent. The microcapsules can be applied to the propellant by spraying. rolling. brushing. or the like. A multi-layered microcapsule protective coating can be applied to the propellant by first applying adhesive to the propellant. then applying a layer of microcapsules. and then repeating the adhesive-microcapsule applications step-wise until the desired thickness of protective coating has been provided.

The protective coating of this invention can be used with caseless ammunition of the telescoped variety wherein the projectile is telescoped into the bore of a hollow cylinder of propellant. or can also be used with the variety of caseless ammunition wherein the propellant charge is secured to the rear face of the projectile.

Thus. it will be readily apparent to those skilled-in the art that the selection of microcapsules of sufficiently fine form can be made so as to permit the building up of several layers of microcapsules on the outside of a round of caseless ammunition thus permitting the formation of an excellent heat transfer barrier at relatively low total weight and under conditions involving a minimum of interference with the final action of the propellant burning. A round covered with such capsules will be highly resistant to ignition by radiant energy and will even resist exposure to flame for significant time periods.

Since many changes and variations of the disclosed embodiment of the invention may be made without departing from the inventive concept. it is not intended to limit the invention otherwise than as required by the appended. claims.

What is claimed is:

1. In a round of caseless ammunition comprising a projectile and a compacted charge of propellant. the improvement comprising a protective coating comprising at least one layer of microencapsulated vaporizable low heat transfer liquid adhered to the outer surface of the propellant charge.

2. A round of caseless ammunition comprising a projectile. a compacted charge of propellant secured to said projectile. and a protective coating secured to an external surface of said propellant charge. said protective coating comprising a plurality of microcapsules of a vaporizable low heat transfer liquid.

3. A round of caseless ammunition comprising a projectile, a compacted charge of propellant secured to a protective coating adhered to an external surface of said charge. said protective coating comprising a plurality of microcapsules of a vaporizable low heat transfer liquid.

6. The propellant charge of claim 5, wherein said liquid is silicone oil.

Patent Citations
Cited PatentFiling datePublication dateApplicantTitle
US1187779 *Oct 2, 1914Jun 20, 1916Ernest B MillerAmmunition.
US1865157 *Oct 11, 1928Jun 28, 1932Remington Arms Co IncLubricant
US2800457 *Jun 30, 1953Jul 23, 1957Ncr CoOil-containing microscopic capsules and method of making them
US3120184 *Apr 22, 1960Feb 4, 1964Universal Match CorpPyrotechnical devices and methods of making the same
US3703868 *Jul 7, 1970Nov 28, 1972Hercules IncProtective surface covering having heat and moisture resistant properties for caseless ammunition
US3727512 *Mar 4, 1970Apr 17, 1973Forges De Zeebrugge SaProcess for the surface treatment of non metallic cases such as cartridges, and the so treated cases
US3730094 *Jun 12, 1970May 1, 1973Us ArmyEnergetic protective coating for caseless ammunition
US3747532 *Apr 2, 1970Jul 24, 1973Henry Wallengerg & Co AbProcess for the manufacture of combustible cases for fuel charges or explosive charges
Referenced by
Citing PatentFiling datePublication dateApplicantTitle
US4098193 *Sep 8, 1976Jul 4, 1978The United States Of America As Represented By The Secretary Of The ArmyWear and corrosion reducing additive for gun propellants
US4282813 *Dec 15, 1978Aug 11, 1981Calspan CorporationTwo piece caseless round and gun therefor
US4285276 *Apr 11, 1980Aug 25, 1981Howard A. FromsonMethod for printing employing lithographic fountain dampening solution
US4306993 *Sep 28, 1978Dec 22, 1981Minnesota Mining And Manufacturing CompanyFor marking objects
US4315785 *Apr 9, 1980Feb 16, 1982The United States Of America As Represented By The Secretary Of The ArmyMicroencapsulated coolant
US4365558 *Dec 7, 1979Dec 28, 1982Societe Nationale Des Poudres Et ExplosifsDelayed self-ignition varnish covering consisting of hollow microspheres in binder
US4399226 *Aug 31, 1981Aug 16, 1983Minnesota Mining And Manufacturing CompanyTagging with microcapsules containing perfluoroalkyl pentafluorosulfide
US4469623 *Aug 24, 1983Sep 4, 1984Minnesota Mining And Manufacturing CompanyVapor permeable microcapsules containing volatile perfluoroalkyl bromide
US4731189 *Sep 29, 1986Mar 15, 1988Gregg Jr George LBullet lubricant and method of compounding said lubricant
US4766812 *Nov 13, 1986Aug 30, 1988L'etat Francais Represente Par Le Delegue Ministeriel Pour L'armementVarnish protecting a caseless or combustible-case round of ammunition against thermoinitiation
US4994203 *Dec 5, 1988Feb 19, 1991Societe Nationale Des Poudres Et ExplosifsPolymerizing emulsion of liquid silicone oil in monomer with block polymer surfactant compatible with both
US5072672 *Nov 1, 1990Dec 17, 1991Societe Nationale Des Poudres Et ExplosifsAmmunition
US5237927 *Oct 21, 1991Aug 24, 1993Olin CorporationEnergetic consumable cartridge case
US5523757 *Feb 11, 1993Jun 4, 1996Resnick; Joseph A.Microcapsule shell filled with molybdenum sulfide; radiation absorber, electrochromic paint
EP0012690A1 *Dec 11, 1979Jun 25, 1980Societe Nationale Des Poudres Et ExplosifsCombustible objects, in particular heat-resistant combustible cartridge cases
U.S. Classification102/431, 102/704, 102/700
International ClassificationF42B5/24, F42B5/196, F42B5/16
Cooperative ClassificationY10S102/70, F42B5/196, Y10S102/704, F42B5/24, F42B5/16
European ClassificationF42B5/24, F42B5/196, F42B5/16