US3463047A - Method of making disintegrating bodies for use as practice ammunition - Google Patents

Description

6, 1969 R. GERMERSHAUSEN 3,

METHOD OF MAKING DISINTEGRATING BODIES FOR USE AS muons AMMUNITION Filed March 10, 1967 lnventoh RaLmunJ er-mem'lmus n "United States Patent 3,463,047 METHOD OF MAKING DISINTEGRATING BODIES FOR USE AS PRACTICE AMMUNITION Raimund Germershausen, Dusseldorf, Germany, assignor to Firma Rheinmetall G.m.b.H., Dusseldorf, Germany Filed Mar. 10, 1967, Ser. No. 622,356 Claims priority, appliclgtigg Germany, Mar. 11, 1966,

US. Cl. 86-23 1 Claim ABSTRACT OF THE DISCLOSURE A method of making practice rounds of ammunition in which equal parts by weight of iron powder Whose particles have a greatly cleft surface and iron powder whose particles have a smooth spherical surface are mixed with a lubricant for example graphite, wax or synthetic resin products and compacted and then placed in a casing.

The invention relates to a method of making disintegrating bodies for use as practice ammunition. The bodies consist of a single-part or multipart molding of a metal powder mixture enclosed in a projectile casing of a plastics material. To the metal powder is added a lubricant which stops caking of the molding on disintegration of the projectile after the latter has left the muzzle of the weapon from which the round of ammunition was fired.

The requirements to be met by a successful practice round are very exacting. Thus, the round, especially if it is to be fired from an automatic weapon, must be equal to the high mechanical stresses which occur during feeding, loading and on firing on the one hand and on the other hand, the round must so disintegrate immediately after leaving the muzzle that it is not able to do damage beyond a certain distance from the muzzle. It is important that the external shape and the weight of such a practice round shall resemble closely those of a live round. In such case, weights per unit of volume of about 6.5 g./cc. are required of the disintegrating body of a practice round for automatic weapons and these densities can be produced from loose material only by means of heavy metal powder which are costly. Thus, as is known, the casing of the round, which is made of cardboard, thin sheet metal or a plastics material is filled with a powdered heavy metal, for example lead powder, to which there is added graphite, talc or the like which is ostensibly intended to prevent the metal powder particles caking together on disintegration of the round.

As agglomeration of the meta 1 powder cannot be achieved satisfactorily by such additions alone, a casing filled with such a charge does not have adequate mechanical strength.

Another method is also known in which the internal cohesion of a molding consisting of iron powder is reduced. The metal powder is first formed into moldings under an applied pressure sufficient to secure a required density, after which the coherence of the powder particles in the moldings is so reduced by a mechanical or chemical action, while retaining the shape of the moldings, that the moldings are able to disperse in fine powder after the round leaves the muzzle.

The mechanical or chemical aftertreatment for the purpose of reducing the cohesion is not only costly, but also is difiicult to reproduce reliably.

It is thus an object of the present invention to avoid these drawbacks and produce moldings of metal powder for disintegrating rounds which correspond in form and weight to a normal live round, which have the necessary mechanical strength and which disintegrate into minute particles, lacking all power of penetration, shortly after leaving the muzzle. Moreover, the rounds must not expose the weapon to unnecessary wear or any damage.

The present invention is based on the surprising discovery that the disintegration properties of iron powder moldings can be considerably improved by a suitable choice of the starting materials as regards the size and nature of the surface of the particles of iron and by adding special lubricants. Such improvement is obtained without the strength required for handling during the manufacture of the round and to withstand the stresses during the feeding and loading process in the weapon being impaired at the same time.

According to the present invention the procedure which is followed in making moldings for disintegrating practice rounds is that iron powder whose particles have a greatly cleft or roughened surface and iron powder whose particles have a smooth spherical surface are subjected, in approximately equal parts by weight, to a mixing treatment with the addition of a lubricant, after which the pourable mixed material is compacted under a load per unit of area of from about 6.5 to about 8.0 tons/sq. cm. into a single-part or multipart molding conforming to the internal shape of the casing.

The interengagement of the cleft or roughened and smooth iron particles does not have a major eifect on the strength of the molding. The addition of the lubricant with its adhesive effect is the main factor affecting the strength.

Another advantage of the lubricant is that it causes the iron particles to slide over one another with reduced friction and interengagement during the compacting operation.

The lubricant itself may consist of a mixture of stearic acid and finely ground Phosphor bronze. The stearic acid is first melted and the Phosphor bronze dust is then introduced into the melt while stirring. This mixture is thereafter cooled while being stirred vigorously. The solidified suspension is then ground until the particle size is a multiple of that of the Phosphor bronze dust introduced. The effect of the lubricant can be further improved by adding paraflin oil.

As a result of the bonding of the iron patricles by the lubricant, there is obtained in particular, good strength at fairly low compacting pressures and, at the same time, reliable reduction of the round to dust in front of the muzzle.

Although it has been found by an extensive series of tests that a mixture of stearic acid and Phosphor bronze is outstandingly suitable as a lubricant and is one which can be mixed very well with the iron powder, other lubricants may be used, among which are, for example, graphits, waxes or synthetic resin products.

By way of example only, methods embodying the invention of producing practice rounds will now be described in greater detail with reference to the accompanying drawing which is a section through the round.

The first method to be described employs the following constituents:

(a) Iron powder whose particles have greatly cleft or roughened surface and a tendency for interengagement, in which the particle sizes are divided as follows.

Percent by weight:

stearic acid and 84 percent by weight of Phosphor bronze powder of particle size about 50 By homogenization of the stearic acid melt and subsequent grinding, a mixture is produced the particle size of which is below 460g.

The proportion by weight of the lubricant in the total weight of a disintegrating body is 3 to 8 percent by weight.

The constituents are mixed together in a mixer with the addition of 2 to cc. of parafiin oil per kilogram of the quantity used until the powder has been completely mixed. The loose material obtained in this way is then compacted at a loading per unit of area of 6.5 to 8 tons/ sq. cm. to produce a body whose shape approximates to that of a projectile.

In a second method the following particularly satisfactory composition is used:

50 percent by weight of an iron powder having particles with smooth spherical iron powder, a particle size of about 250, and a knocking weight of 4.15 g./cc.

45 percent by weight of iron powder whose particles have a greatly cleft or roughened surface with a particle size below 150,11. and a knocking weight of 2.95 g./cc.

5 percent by weight of lubricant 5 cc./kg. of paraffin oil 7,500 kg./sq. cm. pressure of compression.

The constituents are mixed together as before and then compacted to produce a projectile-shaped body.

The drawing shows a disintegrating practice ammunition round which consists essentially of a casing 1 of a plastic material, a long-shanked base part 2 and a reinforcing element 3 arranged in the casing in the zone of the rotating or driving band. Before the reinforcing element is inserted, the disintegrating bodies 4 and 5 consisting respectively of a moulding tapering to a point and a cylindrical moulding into the empty projectile casing 1 are inserted into the casing, after which, once the element 3 has been inserted, the shank of the projectile base 2, which is likewise filled with a disintegrating body 6, is inserted in the projectile casing 1.

Of course, the arrangement may also be such that,

4 with the reinforcing element 3 eliminated, a disintegrating body which is continuous from base to tip is employed as the core of the round.

I claim:

1. A method of preparing a disintegrating practice ammunition round having an outer plastic casing, comprismg:

mixing approximately equal parts of iron powder particles having greatly cleft roughened surfaces with iron powder particles having smooth spherical surfaces,

preparing a lubricant by mixing stearic acid and finely ground Phosphor bronze powder to form mixed particles of a multiple size of the Phosphor bronze particles,

mixingsaid iron particles with said mixed lubricant particles,

pouring the last mentioned mixed materials into a mold adapted to the internal shape of said plastic casing,

pressing said material mixture within said mold under a pressure of 6.5 to 8.0 tons per sq. cm. to form a compact body therefrom,

removing said compact body from said mold, and

inserting said compact body within said plastic casing to form said ammunition round.

References Cited UNITED STATES PATENTS 3,216,358 11/1965 Findeisen l02-92.7

FOREIGN PATENTS 625, 64 7/1946 Great Britain. 718,252 11/1954- Great Britain.

ROBERT F. WHITE, Primary Examiner J. R. HALL, Assistant Examiner US. Cl. X.R.

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