US3854400A

US3854400A - Caseless ammunition and propellant and method of making same

Info

Publication number: US3854400A
Authority: US
Inventors: Langenhoven J Van
Original assignee: Victor Comptometer Corp
Current assignee: Daisy Manufacturing Co Inc
Priority date: 1961-05-03
Filing date: 1968-12-19
Publication date: 1974-12-17
Anticipated expiration: 1991-12-17
Also published as: US3302523A; GB1162951A; US3561319A; DE1728364B1; US3577921A; US3530762A; DE1553937A1; CH456398A; US3545333A; CH550988A; DE1796283B2; DE1796283A1; US3521523A; GB1162953A; US3951038A; GB1162952A

Abstract

There is herein disclosed caseless ammunition having a rigid solid self-supporting porous propellant ignitable by surface contact with high temperature air and methods of making such a propellant with controlled porosity to provide predetermined ignition and propulsion characteristics.

Description

ite States Van Langenhoven CASELESS AMMUNITION AND PROPELLANT AND METHOD OF MAKING SAME Inventor: Jules E. Van Langenhoven, La

l-lulpe, Brussels, Belgium Assignee: Victor Comptometer Corporation,

Chicago, 111.

Filed: Dec. 19, 1968 Appl. No.: 785,317

Related US. Application Data Continuation-impart of Ser. No. 473,556, July 7, 1965, abandoned, Continuation-in-part ofSer. No. 189,621, April 23, 1962, abandoned.

US. Cl 102/38, 86/1, 149/2,

References Cited UNITED STATES PATENTS 1/1896 -Maxim1l 102/101 Hawk 102/D1G. 1

2,230,100 1/1941 Aaron 264/3 E 11/1941 Regestein..... 264/3 D 11/1956 ONeill. Jr. 149/100 6/1962 Andrew et a1. 102/104 X! 6/1963 Cook 102/104 x 12/1964 Silk 264/3 E l0/1965 Quinlan et a1. 102/D1G. 1 6/1907 Maxim 102/100 FOREIGN PATENTS OR APPLICATIONS 412,012 6/1934 Great Britain [OZ/DIG. 1

Primary Examiner-Robert Stahl Attorney, Agent, or Firrr'zBruce G. Klaas ABSTRACT There is herein-disclosed c'aseless ammunition having a rigid solid'self-supporting porous propellant ignitable by surface contact with high temperature air and methods of making such a propellant with controlled porosity to provide predetermined ignition and propulsion characteristics.

, 20 Claims, 3' Drawing Figures BACKGROUND OF THE INVENTION limited to air ignition systems for propelling projectiles,

such as in firearms or the like. The term caseless ammunition, as employed herein, is used in its broad sense to include a projectile-propellant combination in which the propellant is not loosely confined within a container such as a shell; but rather, is a solid selfsupporting material capable of retaining its form without external support. The term projectile, as employed herein, is used in its broad sense to include any and all projectiles in the ordinary sense of the term as well as objects such as studs, bolts, and other fastening devices. The general term propellant is utilized herein to refer to a combustible mixture of materials by which a projectile may be expelled from a firearm or the like. The specific term solid propellant is utilized herein to refer only to relatively large piece propellant as is generally understood in the art and not to relatively small grain gun powder and the like. In the present invention, a large one-piece pellet of the'solid propellant is adapted to be adhered, affixed, or otherwise mechanically bonded to a projectile forming a caseless round of ammunition or the like, and in that form, can readily be handled and disposed in a firing position in a suitable barrel device for guiding the path of travel of the projectile after ignition of the propellant. Firing devices typical of the types to which the present invention is applicable are disclosed in the related applications and patents hereinabove set forth in which reference is made for further details thereof.

Some of the problems involved in the manufacture of a caseless type solid propellant are shrinkage, reliability, stability, cost, and standardization of. ignition and propulsion characteristics in mass production. In accordance with the present invention, self-supporting solid propellant charges can be simply and economically mass produced with new and improved shrinkage, stability, reliability, and consistency in ignition and propulsion characteristics.

BACKGROUND AND PRIOR ART The propellant of this invention is particularly adapted for use in a firearm such as a 0.22 caliber rifle having an air ignition system. Indeed, it may be that the propellant of this invention would be unsatisfactory for other uses and that the characteristics which produce particularly beneficial results in an air ignition system would not be of any importance in other applications.

For example, the manufacture and use of large grain large web solid propellants for rocket propulsion has been given much consideration. in the prior art. In rocket propellants, extreme careh'as been exercised to manufacture dense non-porous propellants ignitable by methods other than an air ignition system. For another example, while porous small gun powder grains have been given prior consideration in connection with firearms, heretofore the use ofsuch small grain porous gun powder has been limited to conventional cartridge type ammunition in which the gun powder is ignitable indirectly by a percussion ignition primer or the like. Prior art porous gun powders for firearms apparently have been small size thin web particles held in cartridge cases and ignited indirectly by use of a percussion responsive primer of fulminate or the like. Such prior art propellants are to be sharply contrasted with the large size large web air ignitable solid porous one-piece propellant pellets of the present invention.

SUMMARY OF THE INVENTION -The foregoing and other advantages and benefits of the present invention are achieved by preparing a wet uniform dough-like extrudable mixture of a dissolved or partially dissolved cellulose nitrate (hereinafter referred to as nitrocellulose), with or without a binder, and having a removable filler. One or more propellant pellets of a desired size and configuration suitable for attachment to a projectile are formed from the wet uniform doughy mass. Thereafter, the filler is removed to fonn voids in the pellets providing a desired porosity therein. The pellets are dried and solidified in the desired shape to form a solid rigid single grain porous propellant. The pellets may be formed separately and then attached to the projectile or they may be formed directly on the projectile. i

In accordance with the presently preferred form of the invention, at least a portion of the filler consists of a particulated solid material insolubleto a solvent used to dissolve the nitrocellulose and soluble by another solvent which is utilized to dissolve and extract the filler from the wet formed pellets thereby producing pores of a controlled size and distribution. A dry nitrocellulose preferably having a relatively high nitrogen content on the order of 13.4 percent is dissolved by a suitable solvent such as acetone to form a gel into which a measured quantity of a filler of particular parti-' cle size, such as potassium nitrate, is mixed and uniformly dispersed throughout the nitrocellulose gel. The mixture is maintained in a wet pasty dough-like extrudable-form until the filler particles have been uniformly dispersed in the nitrocellulose gel. Then the mixture may be dried to cause the dissolved nitrocellulose to harden and set up to form a solid body of nitrocellulose with the filler held in uniform dispersion throughout or the filler may be. removed before the gel hardens. The

filler is removed to create voids in the solid nitrocellulose body. The potassium nitrate filler is removed by water washing until substantially all of the potassium nitrate has been dissolved. Then the solid porous body of nitrocellulose is dried to provide an air ignition propellant.

More particularly, the porous propellant of the present invention is manufactured by a process comprising the steps of l drying a wet commercial nitrocellulose, (2) dissolving the dry nitrocellulose by a suitable solvent such as acetone to produce a wet doughy gel mass, (3) mixing a solid such as potassium nitrate in the wet doughy mass and uniformly distributing the solid throughout the wet doughy mass, (4) extruding the wet doughy admixture of dissolved nitrocellulose and solid into individual thick web pellets-or blocks from which individual thick web pellets may be later-severed, (5) removing the solvent from the extruded pellets or blocks, (6) drying the extruded pellets or blocks to solidify the nitrocellulose and form a solid nitrocellulose matrix with the solid particles uniformly distributed throughout, (7) washing the solidified pellets or blocks with a solid solvent such as water to remove the solid and leave uniformly distributed pores throughout the nitrocellulose matrix, (8) drying the porous nitrocellulose matrix.

' It has been determined that the ratio of the amount of propellant'to the amount of filler particles must be within more or less certain limits to obtain the most beneficial results. Tests indicate that for a 29 grain 0.22 caliber 1,150 f.p.s. round the optimum ratio of propellant to filler particles is l:2 and 125. When the ratio is more than 1:15 or less than 1:4, the results are substantially less beneficial. I

It has'also been determined that the particle size must be within more or less certain limits to obtain the most beneficial results. Tests indicate that for a 29 grain, 0.22 caliber, 1,150 f.p.s. round, the particles which pass through a standarclNo. 120 sieve screen and are retained on a standard No. 140 sieve screen provide optimum results. If the size of the particles is too coarse, the porosity of the propellant is significantly reduced. Tests show that particles which will not pass through a standard No. 100 sieve screen reduce optimum results about 25 percent. If the size of the particles is too fine, the porosity of the propellant is also significantly reduced. Tests show that particles which will pass through a standard No. 200 sieve screen reduce optimum results about 25 percent.

It has also been determined that optimum results depend upon uniform distribution of the'filler in the dissolved nitrocellulose. Tests have shown that multiple extrusions of the admixture prior to removal of the nitrocellulose solvent enhances uniform distribution of the filler particles} 1 I It has also been determined that optimum results depend upon the completeness of removal of the nitrocellulose solvent and the filler. Tests have shown that the shape of the nitrocellulose pellet or block is a factor in securing'satisfactory removal of the solvent and the tiller. It has been determined that a doughnut shaped or tubular shape produces optimum results not only in manufacture of the propellant but also in associating the propellant with a projectile and in ignition and burning of the propellant in a firearm having an air ignition system. a v t Still other advantages and benefits of the present invention will become apparent, upon a reading of the description of the preferred embodiments taken'in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view, partly in section, of an illustrative round of caseless ammunition supported in propellant extrusionapparatu's;

DETAILED DESCRIPTION In General Caseless rounds of ammunition, indicated generally by the reference numeral 10, and shown in detail in FIGS. 1 and 2, are adapted to be positioned within a firing chamber of a suitable firing device. In the illustrative form of the invention, each round comprises a metallic (e.g., lead) slug having a generally cylindrical intermediate section 12 and a front end or nose section 14. Propellant attaching means are provided in the form of a stub rear portion 16, integrally connected to the cylindrical section 12, and terminating in a radially displaced upset portion 18. In the presently preferred form of the invention, a relatively large size one-piece pellet of solid porous propellant 20, generally corresponding in diameter to cylindrical section 12, is fixed to the stub shaft portion 16 and held in place by upset of-ammunition comprise more than one'layer of propellant or propellant portion,- eachof which may be molded, extruded, or otherwise mounted on the projectile. Such additional layers or portions may have successively higher ignition points progressing toward the projectile to provide a greater thrust if so desired, or may be otherwise varied and modifiedto attain particular ignition and firing characteristics. For example, in FIG. 1, the main propellant charge 20 is shown to have an integral semi-spherical ignition portion 22 and, in FIG. 2,

multiple layers

40, 42 are illustrated. In any event, the propellant portion'of the ammunition is in the form of an integral one-piece caseless propellant and the entire round isfired from the gun without resi- The explosive mixture orcompo'sition from which the propellant is made and of which it is formed comprises,'in general, any of the well-known single-base,

double-base or triple-base materials consisting princior smokeless powder. So-called double-base explosives can also be satisfactorily employed for the purposes ofthe present invention :by adding nitroglycerine tothe nitrocellulose in amounts conventionally ranging from about 5 percent 'up to about 40 percent. Similarly, triple-base explosives can bemade by additionally adding nitroguanidine to the nitrocellulose containing the nitroglycerine. The starting nitrocellulose base material can be in anyof the commercially'available forms such as, for example, in the fonn offibers or solventsoftened grains. In the presently preferred system, the

nitrocellulose-is more or less dissolved by a suitable solvent and solvent-softened grains may be most advantageously utilized. In another system, the nitrocellulose is more or less undissolved and the fibrous form may be more advantageously used. In the preferred form, the nitrocellulose base material is more or less dissolved and/or colloidally suspended in a matrix formed form a hardenable gel obtained by dissolving the nitrocellulose and/or a cellulose binder material. In one form of the invention, nitrocellulose may be colloidally suspended in a dissolved binder material with little or no dissolving of the nitrocellulose itself. In forming a hardenable gel of dissolved nitrocellulose any one of a variety of suitable solvents can be satisfactorily employed. Solvents which are particularly suitable for this purpose include acetone, methyl ethyl ketone, and other ketones. These and other solventsknown in the art to be suitable for dissolving nitrocellulose may be used alone or in combination. g Y

While it is presently preferred to form a plain nitrocellulose base material gel, a soluble organic binding agent may be employed with nitrocellulose to form a combination nitrocellulose binder gel which is effective to form a wet pasty or dough-like mixture for shaping, casting, or extrusion thereof into wet slugs'or' pellets of the desired shape and size. Binding agents which are particularly suitable for this purpose include cellulose derivatives such as methylcellulose, hydroxyethyl' cellulose, carboxymethyl cellulose, carboxyethyl cellulose,'

starch, arabic gum, or the like. The quantity of cellusalt system is employed in which water soluble salt parlose binder'material employed is dependent'on the quantity of the various constituents. used in the mixture and the desired propellant characteristics. Inmostinstances,.the cellulose binder material is employed in amounts ranging. from about 3 percent up to about 20 percent by weight based'on the nitrocellulose constituent present, and quantities of about percent by weight are preferred. On-the other hand, the use of the cellulose binder in amounts greater than about percent by weight has been found toeffect an excessive dilution of the explosive charge, preventing the attainment of the desired burning rate and pressure of the explosive when ignited. It is for this reason that the cellulose binder material is usuallyemployed in amounts ranging from about 3 percent up to about 20 percent by weight. a

The conditions of manufacture and use may require additional agents for special purposes.'For example,

The desired porosity of the propellantis obtained by 'material may be in the form of particulate solid such as a salt or in the form ofa removable liquid or a combina tion thereof. In the presently preferred embodiment, a

ticles, such as potassium nitrate; are mixed-with a more or less dissolved nitrocellulose base material and a nitrocellulose solvent such as a methylethyl ketone or acetone in which the salt is insolvent. The solvent forms a wet nitrocellulose gel in which'the solid salt particles are suspended. After or as the gel dries and hardens, the salt particles may be removed bylea'ching with water to form the desired voids. In another formof the invention, a liquid filler is employed'which is subse. quently removed by leaching and/or evaporation as or after the nitrocellulosegel hardens and dries. In either form of the invention, a binder maybe used with the nitrocellulose andthe desired degree'of porosity may be obt ainedby use of either a solid or liquid filler.

In any event, the base material or materials-are blended with a suitable solvent or combination of S01 vents in an amount sufficient to form a wet paste-like or doughy gel mass which can conveniently be molded, cast or extruded into wet pellets of the desired configuration and size. While the quantity of solvent employed to form a salt systemgel is not critical per se, the" amount employed should be adapted to achieve optimum wetness for good forming characteristics, and

must be adapted to achieve the desired porosity of the resultant propellant tothe extent,:if any,flthat thesol- I vent itself forms voids by subsequent removal.

The formation of a uniform wet mixture of the several constituents can be conveniently achieved in any one'of a'variety of mixing apparatus which preferably are provided with ineans'for preventing or'inhibiting the evaporation of the solvent from the' mas's during mixing. After a substantially uniform wet mass of the desired consistency is obtained, the mass can be readily the use of a stabilizer, such as diphenylamine, is generally advantageous and the use of a dye, with the exception of amine or aciddyes, for coloring the final prod-1 uct may be employed. A suitable oxidizing agent may be employed to provide better burning characteristics and suitable breech pressurereducing agents may also,

also be included to provide desired ignition, and rate-.

of-burn characteristics to the resultant propellant as well as to enhance its stability during prolonged periods of storage. Typical accelerating agents include water free nitrates, while a typical stabilizing agent is repre-v sented by diphenylamine. However, the presently preferred forms of the invention have the advantage that no additives are employed other than diphenylamine as necessary to provide sufficient stabilization and safety.

- the present invention and methods of making a solid formed, preferably by extrusion, into a plurality 'of pellets of the desired cross-sectional configuration and of length consistent with its intended end use. The wet pellets aresubsequently dried to provide a dry hard porous nitrocellulose propellant. The resulting propellant can be repeatedly handled, exposed to varying humidity and normal temperature conditions, and stored for long periods of time without deterioration resulting in loss ofexplosive power and velocity during firing.

In order-to illustrate the propellant compositions of porous propellant therewith, the following examples are provided in connection with-the general characterization'of-ffRemovable SolidFiller System andfRemovable Liquid Filler System. I. Removable Particulate Solid Filler System Propel lants g The presently preferred type of propellant is manufactured by use of a removable solid particulate type filler to'obtain the desired degree 'of porosity and is re ferred to as a Solid Filler System" propellant. I

The advantages of the solid filler; system'are that (1) a single homogeneous solid stabilized propellant grain or pellet of uniform porosity is produced for each round of ammunition, (2)the propellant may be mass produced in variable volume from small quantities of a few pounds or less to much larger quantities of hundreds of pounds or more, (3) the propulsion characteristics as measured by energy released and pressures obtained can be more easily controlled and varied by changing propellant density which is primarily a function of the nitrocellulose-solid filler ratio and the particulate size or sizes, (4) the ignition characteristics are more easily controlled and the resultant propellant is more easily ignited and therefore better suited to air ignition, and (5) the burning characteristics are more easily controlled and the resultant propellant has a higher flame propogation rate. Control of these various characteristics may be effectuated by simultaneously or independently varying (l) the ratio of volume of propellant to volume of pores or voids (i.e., porosity) or (2) the amount of surface area. It will be seen that the volume of propellant to pores is a function of the amount and distribution of propellant and solid filler particles while the amount of surface area of the propellant is a function of the number and size and distribution of the solid filler particles. It may further be seen that l ignition characteristics are primarily a function of surface area exposed to the hot ignition air, (2) the rate of flame propagation is primarily a function of porosity, and (3) the energy released and pressures generated are primarily a function of the completeness and speed of burning of the propellant.

In general, the ingredients of the preferred formulation comprise:

1. Nitrocellulose initially dry.

2. A solvent of nitrocellulose such as acetone.-

3. A stabilizing agent for nitrocellulose subjected to extended-storage, such as diphenylamine.

4. A solid filler material which is soluble in some leaching solution, such as water, in which nitrocellulose is not soluble. The filler material must be capable of being ground or otherwise divided into various sizes of particles which maybe graded such as by sieving. It must also be nontoxic and noncorrosive in small residual quantities (5 percent or less) in the finished round. Potassium nitrate is a suitable filler. Other suitable fillers for leaching with water are sugars, sodium chloride, urea and many others.

In general the production process comprises the step 1. Mixing the desired ratio by weight of nitrocellulose and solid particulate filler in the desired quantity, the tiller having been previously ground and graded so that a known discrete particle size or combination of discrete particle. sizes is used.

2. Dissolving a stabilizing agent, such as diphenylamine, in the solvent.

3. Mixing the dry nitrocellulose and solid filler, previously mixed, with the solvent and stabilizing agent. This mixing is done in such a manner that a homogeneous wet dough-like gel is produced and the escape of the volatile solvent is minimized. At this point the nitrocellulose is partially or completely dissolved in the solvent while the solid particulate filler retains its physical identity as to both composition and particle shape and size.

4. After mixing, the dough-like gel is placed in some apparatus capable of molding the gel into grains of a desired size either as separate propellant pellets or propellant blocks of a desired shape and size while taking suitable steps to minimize solvent loss.

5. After forming the propellant grain, pellet,- or

block, the solvent is evaporated or dissolved from the molded grain either in air or water until it is pysically strong enough to allow further processing and the quantity of remaining solvent is small enough that excessive expansion will not occur within the just molded propellant grain.

6. The just molded propellant is then placed into a boiling bath with either thermal or mechanical agitation to dissolve the filler material from the now precipitated nitrocellulose and diphenylamine. The potassium nitrate being soluble in water and the nitrocellulose being insoluble in water, the filler material may be essentially removed leaving a porous but hard structure of nitrocellulose containing a stabilizing agent and a small residual quantity of the filler material.

7. The final step in the process is to remove the water entrapped in and on the propellant by drying, prefe'rably in warm air or an oven.

Thus, in effect, voids are cast into a precipitating propellant gel by dissolving out solid filler particles used as patterns for these voids.

In a propellant of given volume, the propellant weight may be varied by viaration of the ratio of nitrocellulose to filler. Tests indicate that a propellant for obtaining velocities on the order of l,l0( )-l,'200 f.p.s. of a 29 grain 0.22 caliber projectile requires a nitrocellulose-filler ratio of between 1:15 and 1:5. However, particularly advantageous results have been obtained in the ratio range of 1:2 to 1:4 and the presently preferred ratio is 1:2. Contrary to what might be expected, tests indicate that the relationship between propellant weight and the nitrocellulose-filler ratio is not linear due to a requirement for increased percentages of solvent as the ratio decreases to maintain the necessary fluidity of the mixture for thorough mixing and extrusion. Tests indicate the following approximate propellant weight relationship to the nitrocellulose-filler ratio: 1:1 (80 mg); 1:2 (60 mg); 1:4 (42 mg); 1:5 (37 mg).

As a general rule, it appears that time between applica- 'chamber pressures increase as propellant weight increases. Projectile velocities increase as propellant weight increases.

In addition to variations in the nitrocellulose-filler ratio, variations in density and surface area of the propellant greatly affect performance. The two basic factors which affect density and surface area are the nitrocellulosefiller ratio and the size of the voids created by removal of the fillenThus, with a salt filler the size of the salt determines the surface area. In general, for a given size projectile and propellant weight and with certain upper and lower limits, firing chamber pressures, projectile velocity, and ease of propellant ignition increase as surface area increases. By proper control and selection of these various parameters, a propellant can be manufactured which will consistently provide optimum results at room temperature and medium humidity with a 29 grain 0.22 caliber projectile of muzzle velocities of 1,150 i 40 fps, firing chamber pressures of between 12,000 and 30,000 psi, and ignition times of approximately 0.6 milliseconds. The optimum propellant has approximately between 60-85 percent (approximately percent presently preferred) voids and a density of approximately 0.520 grams per cubic centimeter in 1:2 nitrocellulose-filler ratio, approximately 0.558 g/cc in a 1:15 ratio and 0.343 g/cc in a 1:4 ratio.

The nitrocellulose is a commercially available grade (N 13.35 13.45 percent) sold by Hercules Powder Company as hereinbefore described. In the illustrative examples, it is utilized in a dry condition without water. The potassium nitrateis used as a solid particulate filler which is subsequently removed to produce the desired porosity in the propellant. The diphenylamine is a stabilizer, as is conventional, and the acetone is a solvent which destroys the fiber structure of the nitrocellulose and forms a doughy non-fibrous gel mass.

The presently preferred filler is a commercially available technical grade potassium nitrate which is not available in particle sizes suited to the requirements of the present invention. In order to obtain the desired particles of the present invention, it is necessary to process the commercially available potassium nitrate as by ball milling which has proved to be a particularly satisfactory way of obtaining more or less standardization of particle size distribution to obtain more or less standardized ballistic performance between various batches of propellant. While the ball milling apparatus may be varied as necessary or desirable, satisfactory results have been obtained by grinding one-pound batches of technical grade potassium nitrate with 80 .2 grams The potassim nitrate of Examples 1-3 is'graded to particle sizes which will pass through a No. 100 sieve and be retained on a No. 120 sieve. Some other range of particle sizes could be used. A change in particle size would require an adjustment in acetone quantity and would result in somewhat different ballistic characteristics. Usually, a larger quantity of acetone is required with a finer average KNO particle size in order to produce an extrudable dough. The ease of extracting the KNO after extrusion also decreases as the average particle size decreases. Since the surface area of the KNO; and thus of the nitrocellulose in the finished propellant is a function of the average particle size, those properties affected by surface area would change with particle size change. A finer average particle size would increase the ease of ignition, rate of burning, and maximum chamber pressure produced in a given gun. All of the above effects stated for a decrease in particle size would be reversed if the particle size were made coarser. This discussion assumes that they propellant density remains essentially unchanged. The following is an illustrative example of a propellant with a wide range of particle sizes and a substantial concentration of the coarser sizes:

Example 4 grams ttroce u ose (1335-4591 N. dry) grams Potassium nitrate (particle size distribution A'as below) Diphenylamine cc Acetone Particle Size Distribution A porcelain balls, 0.5 inch in diameter, in a 0.5 gallon ball jar rotated axially at 84 rpm. The ground batches are caused to pass through and onto five fractionating screens including'US. Standard sieve sizes of 70, ,l00, 120, 140, 200, and a fines recovery pan. Then the various size particles may be recombined in any desired combination of particle sizes, if desired, or an original or simulated grind may be used in its entirety.

The following formulations and particle size distributions are illustrative of the foregoing:

It should be realized that this distribution of particle sizes might be the natural distribution obtained from a particular grinding configuration and procedure or it might be produced by blending graded particles. Regardless of how this or any of the almost infinite number of other possible distributions might be obtained it has as its purpose a measure of control over the final propellant surface area and thus of its final ballistic characteristics.

The ability to control surface area along with the ability to control propellant density by choice of nitrocellulose to potassium nitrate ratio provide wide flexibility. For example, in order to decrease the density and thus increase the surface area, the ratio of filler salt to nitrocellulose in Example 1 may be altered as shown in Example 3. In order to increase the surface area, the average particle size of the filler salt might be decreased either by choosing (l) a particle size distribution defined by two finer sieves than used in Examples l-3 such as through No. 120 sieve and retained in No.

140 sieve; or (2) a distribution of particle sizes defined by a large percentage of the finer grades and a lesser percentage of the coarser grades than used in Example 4, distribution A, as indicated by the following:

Particle Size Distribution B grams through a No. 60 do. 20 do. l0 do. 20 do. 20 do.

30 sieve and retained on a No. 70 sieve 7O do. I00 do. do. do. 120 do. do. 140 do. 200 do. 200 sieve or (3) any combination of the above to increase the surface area.

The method of mixing and preparing the foregoing propellant formulations comprises pre-blending of the diphenylamine and the acetone and then mixing of the entire formulation in a closedcontainer for about 1 hour. The material maybe mixed in an ordinary kneading machine or it may be repeatedly extruded through an orifice plate. By way of example, during mixing by extrusion, it is important to maintain uniform extrusion speed. After the final extrusion, which may be the fifth extrusion, the extruded material may be hung to dry at room temperature for approximately 15 hours to minimize dimensional distortion. The propellant material may be molded as a solid body or it may be extruded in tubular or solid cylindrical or other forms. For example, extrusion with a 0.250 inch nozzle and a 0.062 inch pin will produce, after washing and drying, a propellant pellet having an outside diameter of about 0.220 inch and an inside diameter of about 0.045 inch. When the material has been dried, it may be cut to the desired lengths with a slotting saw. After cutting, the potassium nitrate is removed from the pellets by washing the pellets for approximately 4 days in slowly running water at about 140F. Thereafter, the propellant pellets are dried for approximately 24 hours and then the still wet propellant may be pressed onto the post at the rear of the projectile. It is to be understood that the propellant also maybe extruded onto the projectile or molded thereon.

II. LIQUID FILLER SYSTEM PROPELLANTS Another type of l,l00-l ,200 fps. propellant is manufactured by use of a removable liquid filler to obtain the desired porosity and is referred to as a Liquid Filler System." Some of the advantages of a liquid filler system appear to be reduction in cost of manufacture,

substantial elimination of shrinkage, ease of varying porosity, and ease of standardization of porosity. In the presently preferred formulations, the liquid filler is tol-' uene which is utilized with a cellulose solvent such as acetone and an alcohol wet nitrocellulose. The proportions of the solvent acetone, alcohol, and the filler toluene appear to be particularly significant. With too low acetone percentages, the nitrocellulose does not thoroughly dissolve and a rather fibrous propellant is obtained which produces too high breech pressures. If too high acetone percentages are utilized, the propellant becomes very hard and difficult to ignite and shrinkage is greatly increased. Good results have been obtained with the following formulations:

Example 5 50.0 grams Nitrocellulose (l3.3-l3.5% N dry) 5.0 grams Binder (Ethyl-cellulose K-SOOO) 0.5 grams Stabilizer (Diphenylamine) 60 cc Filler (Toluene) 30 cc Alcohol (Ethyl or isopropyl) 10 cc Solvent (Acetone) Example 6 50.0 grams Nitrocellulose (l3.3-l3.5% N dry) 5.0 grams Binder (Ethyl-cellulose K-SOOO) 0.5 grams Stabilizer (Diphenylamine) 54 cc Filler (Toluene) 27 cc Alcohol (Ethyl or isopropyl) 9 cc Solvent (Acetone) Example 7 K 50.0 grams Nitrocellulose (l3.3l3.5% N 'dry) 5.0 grams Binder (Ethyl-cellulose N-'300) 0.5 grams Stabilizer (Diphenylamine) 42.0 cc Filler (Toluene) 2i .0 cc Alcohol (Ethyl or isopropyl) 7.0 cc Solvent (Acetone) 50.0 grams Nitrocellulose (l3.3l3.5% N dry) 5.0 grams Binder (Ethyl-cellulose N-300) 0.5 grams Stabilizer (Diphenylamine) 36.0 cc Filler (Toluene) l8.0 cc Alcohol (Ethyl or isopropyl) 6.0 cc Solvent (Acetone) When the amount of filler is reduced, the porosity is reduced. Molding of these formulations in a cylindrical cavity 10mm deep and 6mm diameter produces propellant pellets weighing 100, 125, I60, and 175 milligrams, respectively.

It will be understood that the nitrocellulose is alcohol wet as obtained commercially and that sufficient additional alcohol is added to obtain the specified quantity in each formulation. The additional alcohol, filler, solvent, and stabilizer are mixed separately. Then the binder is added, while stirring, in an air tight container and completely dissolved to obtain a smooth flowing syrup-like solution or gel. Then the alcohol wet nitrocellulose is added and mixed in an air tight kneading machine for approximately /2 hour at room temperature. The propellant is then ready for molding or extrusion into the desired propellant shape directly onto the back of the projectile slug as in FIG. 1 or separately.

Immediately after molding or extrusion, the propellant is placed in a water bath at room temperature wherein the nitrocellulose gel and the ethyl-cellulose will be gradually precipitated and hardened as the alcohol and acetone are dissolved. Since the propellant hardens with the filler trapped therein, shrinkage is practically eliminated. The water penetrates through the propellant because of the presence of the alcohol and acetone while the toluene remains unchanged and dispersed throughout the propellant. The greatest part of the alcohol and acetone is dissolved in the water. While the toluene is insoluble in the water, it will be removed therewith by subsequent boiling in water. Thus, the toluene filler is removed by boiling the propellant in water and the vapors may be condensed to recover the toluene. For some unknown reason, these propellants produce lower breech pressures and higher velocities with 0.22 caliber 29 grain ammunition.

In order to promote adherence of the propellant to the projectile, the projectile may be cleaned by naptha or trichlorethylene vapors or the like and then dried. Next a coating of a mixture of 10 grams of nitrocellulose (12% N plastified with 18 percent butylphtalate (viscosity 9% sec.), and cc of acetone may be applied as by spraying while tumbling the projectile in a drum until dry.. Then the projectile is placed in a molding cavity and the propellant dough is injected with' regular force until the cavity is filled.

With the formulations of Examples 6-9, immediately after molding, the ammunition should be immersed in a water bath at room temperature for a time sufficient to precipitate out the nitrocellulose gel and the ethylcellulose. The propellant is soft and has a glazy appearanceafter molding. In the water bath, the appearance changes to white opaque and the propellant hardens. The alcohols and acetone. are dissolved in the water bath so that only the toluene remains. Then the ammunition is boiled in the water for about /2 hour to remove the toluene which can be recovered in a suitable condenser. It may be desirable to coat the ammunition by dipping or by tumbling. In dipping, a sharp instrument such as a pin or needle may be inserted into the propellant to support the ammunition for dipping into a solution of 10 grams nitrocellulose (12% N 18 percent butylphtalate /2 sec. viscosity) and 90cc acetone which may also contain any suitable dyestaff soluble in acetone or a powdered metal or graphite to give a metallic appearance. The needle hole will aid in ignition of the propellant. The ammunition should be dipped projectile end first and then immediately removed and completely dried. It may be desirable to blow dry the coating and then oven dry the propellant at, for example, 50c until completely dry. The coating may also be applied during a tumbling operation with a spray gun.

Another type of liquid filler system propellant comprising more orless undissolved nitrocellulose in a porous binder is manufactured by use of a water filler to obtain the desired degree of porosity. Two exemplary formulations are as follows:

Example I 200 grams Nitrocellulose (13.5% N; 30% water by weight) 1 gram Diphenylamine 5 grams Hydroxyethyl cellulose (dry) l0 grams Potassium nitrate 5 cc Castor oil grams Aluminum stearate 110 cc Acetone 50 cc Water Example 1 l 200 grams Nitrocellulose 13.35% N: 30% water by weight) 5 grams Hydroxyethyl cellulose 10 grams Potassium nitrate l gram Diphenylamine 150 cc Acetone 85 cc Water The nitrocellulose is a commercial grade (N 13.35 13.45 percent) available from Hercules Powder Company or DuPont. It is made from cotton linters with a fineness of 85 to 105 ml and a viscosity of 8 to seconds. It has an ether-alcohol solubility of ll percent and is manufactured in accordance with MIL-N-244. The diphenylamine is utilized as a stabilizer as is conventional. The hydroxyethyl cellulose is sold under the trade name of Natrosol by Hercules Powder Company and has a high viscosity (e. g., 4,000 centipoises). It provides a water soluble binder. Other types of water soluble binders might be used such as methyl cellulose, cellulose monochloracetate, ethyl hydroxyethyl cellulose. The potassium nitrate is utilized as an accelerator due to its ability to liberate oxygen during burning of the propellant. It may be varied in amountor deleted as necessary or desirable. Castor oil may be utilized for lubricating purposes both in the manufacture of the propellant during extrusion and in use in the gun. The

aluminum stearate acts as an inhibitor or retardant to reduce the rate of burning and breech pressures. It has been determined that the castor oil and aluminum stearate may be advantageously deleted in some applications. The acetone is a solvent for the water soluble binder and the diphenylamine and acts with the water to form a filler, which is subsequently removed to obtain the desired porosity, and to dissolve and disperse the binder throughout the nitrocellulose, the fiber structure of the nitrocellulose remaining substantially unchanged.

The method of mixing and preparing the foregoing formulations of Examples 10 and 11 comprises initially,

establishing the water content of the wet nitrocellulose I and adjusting the water content as necessary to obtain 30 percent water by weight so that the 200 grams of nitrocellulose will obtain 140 grams of dry nitrocellulose and 60 grams of water. Then 200 grams of the wet nitrocellulose (water wet 30 percent by weight) is added to 5 grams of the hydroxyethyl cellulose (dry). The nitrocellulose and hydroxyethylcellulose are mixed by tumbling in a closed container for approximately ten minutes at 140F. It is desirable to keep the mix in the container for an additional time (e.g., approximately 20 minutes) until the water soluble binder has begun to swell. The the mix may be cooled to room temperature, whereupon the potassium nitrate and the aluminum stearate are added to the mixture if used. Then the diphenylamine, and the castor oil if used, are dissolved in the acetone and added to the mixture. It is then desirable to tumble the mixture in a closed container for about 5 minutes and then transfer the tumbled mixture to a closer mixer for mixing approximately 30 minutes. At this time, it is desirable to add $000 of water and mix for another 30 minutes. As a result of the foregoing, the water soluble binder is dispersed throughout the nitro' cellulose fibers in a pasty doughy mass and is ready to be molded onto the projectiles.

Any of the various formulations disclosed herein may be associated with a projectile of the type shown in FIG. 1 by use of

suitable die apparatus

30,32 enclosing the stub shaft portion and forming a die cavity 34 therearound approximately equal to the diameter of the projectile with suitable allowance for shrinkage and the like. The exemplary projectile is 0.22 caliber and 29 grain weight. The length of the round of ammunition is on the order of 0.5 inch and the present preferred length of the propellant portion is 0.232 inch. It is to be understood that the length and diameter of the propellant may be varied as necessary or desirable to achieve the desired results. However, in order to clearly differentiate over prior art gun powders and/or wafer thin propellant webs of small size, the term pellet or slug is utilized herein to refer to a large size large web propellant body having a length in excess of 0.125 inch and a diameter of thickness in excess of 0.15 inch. Also, the volume of the propellant is ,on the order of 0.008985 cubic inch but the volume and weight of the propellant may also vary to a considerable extent depending upon the results desired. With a 0.22 caliber projectile, the propellant weights generally will be in a range of 35 to milligrams with the range 'of 50 to 60 milligrams being presently preferred. The doughy mass is extruded through a nozzle or molded or the like 36 into the die cavity around the stub shaft portion. The propellant dough is confined so that it cannot flow past the projectile and enough propellant dough is injected to fill the die cavity and produce the desired length and diameter pellet when dry. The molded propellant is then subjected to further processing to remove the filler and produce the voids resulting in the desired degree of porosity. A main charge formulation such as Example 1 may be used by itself or in combination with a second formulation, such as Example 3, as an ignition charge 38 located at the center rear as shown in FIG. 1 so as to be directly in line with the hot air inlet in an air ignition firearm. The main charge 20 is extruded onto the projectile first as hereinbefore described. Immediately thereafter, the projectile and main charge are displaced slightly in the die means and an ignition charge 38 may be extruded into the rear of the main charge. In the presently preferred form, shown in FIG. I

l, the ignition charge is centrally placed in the rear of the main charge in a somewhat semi-spherical form surrounded with and embedded in the main charge except for an exposed rear surface.

In order to vary the velocity, it may be desirable to change the amount of propellant of any given formulation attached to the projectile. However, it is necessary and desirable to have the dimensions of the ammunition remain constant. An inert charge may be first extruded onto the projectile to occupy a portion of the volume of the normal propellant cavity. An exemplary formulation for the inert charge comprises:

100 gramsTalcum 5 grams l-Iydroxyethyl cellulose (high viscosity) grams Water A technical grade of talcum powder such as that sold by Fisher Scientific Company has been found to be satisfactory. This mixture should be kneaded into a doughy mass for approximately 30 minutes at room temperature before being extruded. It is important that the inert dough have sufficient consistency to set up on the projectile without tending to flow past the projectile. In one illustrative arrangement, shown in FIG. 2, a projectile velocity of approximately 700 feet per second may be obtained by combining an 1,100 feet per second main charge propellant with a volume of inert charge 40. First an inert charge .130 long is molded onto the rear of the projectile and then a quantity of the 1,100 feet per second main charge propellant of Example 1 0.090 long is molded onto the rear of the inert charge. This amount of the propellant will produce a velocity of approximately 700 feet per second.

Advantages of these propellants are that they may be economically manufactured, they are stable both in manufacture and use under normal conditions, they may be easily associated with a projectile to form caseless type ammunition, and they will burn cleanly and minimize corrosion of the gun parts. Furthermore, while being stable and harmless in association with a projectile during manufacture, storage and handling, when properly positioned in a firing chamber of a gun, they are capable of being ignited and generating high energy gases, which when properly confined, are capable of propelling a projectile through a gun barrel at high velocity. While the propellant can be easily ignited in a firing chamber at temperatures of 400-600F as well as in the open by a flame from a match or the like. Until confined, the propellant merelyquickly burns causing no movement of the projectile and is completely harmless. In addition, the propellants and the methods of making them provide versatility and flexibility to enable propellants of varying degrees of porosity to be obtained in a manner which is simpler and more economical than previously known.

The rate of burning of the propellant is easily varied and may be low or quite high. Tests show that the propellant of the presently preferred 0.22 caliber 29 grain 1,150 f.p.s. ammunition will burn completely in one or two milliseconds under ordinary conditions. The preferred propellant has a porosity such that the amount of surface area over which the burning may be propagated may be very large. Thus, the propellant of the present invention has a porosity of approximately 60 to 85 percent voids and approximately 75 percent voids is presently preferred. Furthermore, the numerous pores provide pockets of air and enhance the formation of hot spots by adiabatic compression thereby further increasing the rate of burning. A relatively small amount of nitrocellulose material can be utilized to obtain projectile velocities. The propellant of the present invention may be characterized as a solid large web one-piece pellet of nitrocellulose product having a porosity in the presently preferred embodiments of approximately percent voids and a high burning rate and being easily ignitable by hot compressed'air.

While it will be apparent that the invention disclosed 5 herein is well calculated to fulfill the objects above stated, it will be appreciated that the invention is susceptible to modification, variation and change without departing from the proper scope or fair meaning of the subjoined claims.

I claim:

1. A propellant charge for small arms ammunition consisting of a single grain having a porous structure, which is produced by mixing to parts by weight of a water soluble substance having a limited particle size in a range between 0030mm and 025mm with 100 parts by weight of propellant composition, kneading the resulting composition with addition of solvent, forming the kneaded mixture into a desired shape to 20 obtain a green grain, and immersing the thus obtained green grain in water for several days to elute out the water soluble substance homogeneously dispersed therein, drying the obtained grain, combining with the propellant charge a priming device at one end thereof and a bullet at the other end thereof to form a caseless cartridge.

2. Caseless ammunition for a small caliber firearm or the like comprising a projectile portion and a propellant portion of generally similar size and shape, the propellant portion being formed of a large hard porous body of ungranulated colloided nitrocellulose manufactured by the steps of:

l. mixing nitrocellulose and a nitrocellulose solvent and a removable filler to form a wet extrudable doughy mass of gelatinized nitrocellulose having the removable filler uniformly dispersed throughout,

2. forming a large body of nitrocellulose from the wet extrudable doughy mass and of a size and shape generally corresponding to the size and shape of the propellant portion of the ammunition and with the removable filler uniformly dispersed throughout,

3. removing the filler from the large body of nitrocellulose to provide a large porous body of nitrocellulose, and

4. drying and hardening the large porous body of nitrocellulose.

3. Caseless ammunition for a firearm comprising a projectile portion and a relatively large solid one piece porous ungranulated propellant portion manufactured by the process comprising the steps of:

1. forming a wet uniformly mixed doughy gelatinized mass of a composition of nitrocellulose, a nitrocellulose solvent, and a removable filler,

2. forming a relatively large one piece ungranulated propellant body of nitrocellulose and removable filler from the wet uniformly mixed doughy gelatinized mass, the body being of predetermined size and shape equal to or greater in size than the propellant portion;

3. removing the filler from the ungranulated propellant body to form voids in the nitrocellulose,

4. hardening and drying the propellant body in ungranulated form while retaining the voids to provide a desired degree of porosity, and

5. mounting the propellant body in association with the projectile without granulation.

lant body and then mounted on the projectile portion.

6.'The invention as defined in claim 3 and the composition being formed approximately in the ratio of 1 part nitrocellulose and 24 parts of removable filler.

7. The invention as defined in claim 3 and the composition being formed approximately in the ratio of 1 part nitrocellulose and 2 parts removable filler.

8. The invention as defined in claim 3 and the composition being formed approximately in the ratio of 1 part nitrocellulose and 3 parts removable filler.

9. The invention as defined in claim 3 and the composition being formed approximately in the ratio of 1 part nitrocellulose and 4 parts removable filler.

10. The invention as defined in claim 3 and the removable filler being a solid particulate material.

11. The invention as defined in claim 3 and the solid particulate removable filler being of predetermined size.

12. The inventionas defined in claim 3 and the solid particulate filler comprising particles approximately of a size such as to pass through a No. 100 sieve and be retained on a No. 120 sieve.

13. The invention as defined in claim 3 and the removable filler being a liquid.

14. The invention as defined in claim 3 and the composition further including a cellulose binder.

15. The invention as defined in claim 3 and the removable filler being toluene.

16. The invention as defined in claim 3 and the celluthen a cellulose binder is added and mixed, and then the nitrocellulose is added and mixed.

19. Caseless ammunition for a firearm comprising a projectile portion and a propellant portion manufactured by a process comprising the steps of:

1. forming a wet uniformly mixed doughy mass of a composition of nitrocellulose, a nitrocellulose solvent, and a removable filler;

2. forming a propellant body of predetermined size and shape equal to or greater in size than the pro: pellant portion from the wet uniformly mixed doughy mass;

3. removing the filler to form voids in the nitrocellulose;

4. mounting the propellant body on the projectile portion, and

5. hardening and drying the propellant body while retaining the voids to provide a desired degree of porosity.

20. Caseless ammunition comprising a projectile portion and a propellant portion manufactured by a process comprising the steps of:

1. manufacturing a large hard porous body of ungranulated colloided nitrocellulose by a. mixing nitrocellulose and a nitrocellulose solvent and a removable filler to form a wet extrudable doughy mass of gelatinized nitrocellulose having the removable filler uniformly dispersed throughout,

b. forming a large body of ungranulated nitrocellulose from the wet extrudable doughy mass and of a size and shapegenerally corresponding to the size and shape of the propellant portion of the ammunition and with the removable filler uniformly dispersed throughout,

cfremoving the filler from the large body of ungranulated nitrocellulose to provide a large porous body of nitrocellulose,

d. drying and hardening the large porous body of ungranulated nitrocellulose to provide a large hard porous body of ungranulated colloided nitrocellulose; and

2. permanently attaching the large hard porous body of ungranulated colloided nitrocellulose to the projectile without further change in the composition or general size of the body with at least one surface of said body being uncovered and exposed for direct contact with hot ignition air.

Claims

1. A PROPELLANT CHARGE FOR SMALL ARMS AMMUNITION CONSISTING OF A SINGLE GRAIN HAVING A POROUS STRUCTURE, WHICH IS PRODUCED BY MIXING 100 TO 150 PARTS BY WEIGHT OF A WATER SOLUBLE SUBSTANCE HAVING A LIMITED PARTICLE SIZE IN A RANGE BETWEEN 0.030MM AND 0.25MM WITH 100 PARTS BY WEIGHT OF PROPELLANT COMPOSITION, KNEADING THE RESULTING COMPOSITION WITH ADDITION OF SOLVENT, FORMING THE KNEADED MIXTURE INTO A DESIRED SHAPE TO OBTAIN A GREEN GRAIN, AND IMMERSING THE THUS OBTAINED GREEN GRAIN IN WATER FOR SEVERAL DAYS TO ELUTE OUT THE WATER SOLUBLE SUBSTANCE HOMOGENEOUSLY DISPERSED THEREIN, DRYING THE OBTAINED GRAIN, COMBINING WITH THE PROPELLANT CHARGE A PRINTING DEVICE AT ONE END THEREOF AND A BULLET AT THE OTHER END THEREOF TO FORM A CASELESS CARTRIDGE.

2. forming a propellant body of predetermined size and shape equal to or greater in size than the propellant portion from the wet uniformly mixed doughy mass;

3. removing the filler to form voids in the nitrocellulose;

4. drying and hardening the large porous body of nitrocellulose.

4. The invention as defined in claim 3 and the propellant body being mounted on the projectile portion prior to hardening and drying.

4. mounting the propellant body on the projectile portion, and

5. The invention as defined in claim 3 and the propellant body being larger than the propellant portion, and the propellant portion being severed from the propellant body and then mounted on the projectile portion.

6. The invention as defined in claim 3 and the composition being formed approximately in the ratio of 1 part nitrocellulose and 2-4 parts of removable filler.

12. The invention as defined in claim 3 and the solid particulate filler comprising particles approximately of a size such as to pass through a No. 100 sieve and be retained on a No. 120 sieve.

15. The invention as defined in claim 3 and the removable filler being toluene.

16. The invention as defined in claim 3 and the cellulose solvent being acetone.

17. The invention as defined in claim 3 and the composition further comprising alcohol.

18. The invention as defined in claim 3 and wherein the toluene, alcohol, and acetone are separately mixed, then a cellulose binder is added and mixed, and then the nitrocellulose is added and mixed.