US 5,657,568 AGrant
Composite/Metallic Gun Barrel Having a Differing, Restrictive Coefficient of Thermal Expansion
Issue Date:1997-08-19
•17 Claims
•4 Drawing Sheets
Abstract
A composite/metallic gun barrel is disclosed having a metallic liner and alternating first and second groups of fibers wrapped about the liner, the first groups being disposed in a first orientation generally perpendicular to the long axis of the liner, and the second groups including one or more layers disposed generally parallel with the long axis of the metallic liner. By controlling the amount of fibers in each group relative to the other group, the coefficients of thermal expansion in the radial direction can be regulated to provide a gun barrel having desired firing characteristics.
Metadata
Assignee
- Christensen; Roland J.
Inventor
- Roland J. Christensen
Application Information
Application Number:US 5736935
Filing Date:1995-12-18
Priority Date:1995-12-18
Art Unit:221
Classifications
IPC:
F41A 2100
Field of Search:
42892976.02;76.01161.1;1.11
Patent Drawings (4 sheets)
Description
Background of the Invention
The present invention relates to composite gun barrels for small arms, and in particular, to a gun barrel for small arms wherein the gun barrel is made with a composite portion and a metallic portion formed so that the coefficient of expansion of the composite is contrasted in the radial direction relative to that of the metal portion of the gun barrel and has 0 or nearly 0 coefficient of thermal expansion in the axial direction so as to achieve desiring firing characteristics for the gun barrel.
The use of composite/metallic gun barrels is well known in the art of weapons manufacturing. Typically, composite/metallic gun barrels are made from thin-walled cylinders of metal which are overlaid with a composite material. The composite layer provides increased strength and stiffness to the gun barrel, while simultaneously reducing the weight of the barrel. Thus, a gun simultaneously can be made lighter, stronger and stiffer by not using a conventional metallic barrel.
In most attempts to replace the conventional barrel, however, a thin metallic barrel liner is used. Typically, the metallic portion of the barrel will be less than one-tenth of an inch thick along most of the length of the barrel. The metallic liner serves two major purposes. First, the metallic barrel liner provides a hard, machinable surface for spiral riflings in the liner bore which provide a rotational spin to the bullet during flight and greatly improves accuracy. In contrast, a composite material is not sufficiently hard, is friable, and is otherwise unsuitable for barrel riflings. Second, the metallic barrel liner is used to shield the composite material from the hot, corrosive gasses generated when firing a bullet. As the powder burns to propel the bullet through the barrel, the hot gasses formed by the burning powder to propel the bullet contact the barrel. Those skilled in the art will appreciate that such gasses can weaken the composite material under certain circumstances.
One problem which has developed with barrels having a metallic liner surrounded by composite is that they often fail to operate as desired when repeatedly fired. As a gun is fired several times in rapid succession, the heat generated from the firing of each bullet begins to accumulate in the barrel. Because the metal liner and the composite materials generally have somewhat different coefficients of expansion when exposed to heat, a barrel heated by repeated firing can quickly loose its accuracy and consistency. This is due in large part to prior art lack of awareness and/or inability to form composite/metallic gun barrels, wherein the coefficients of thermal expansion are correlated to the desired use of the barrel.
In apparent attempts to overcome such problems of the prior art, the present level of skill in the art teaches that it is best to select a metallic liner having a coefficient of thermal expansion in the radial direction which matches the expansion coefficient of the composite being used in the radial direction. This involves the process of first identifying the coefficient of thermal expansion for the composite and then selecting amid a limited number of suitable metals to try and match that same coefficient of thermal expansion. However, as will be appreciated by those skilled in the art, the search for such a combination of a specific metallic liner with a similar expansion coefficient to a composite material may not provide the desired characteristics in other areas, such as strength and durability.
Thus, there is a need for a composite/metallic barrel which is formed so that the composite, the metal and their expansion coefficients provide desired characteristics during firing. For example, when such barrel is used for a gun which rapidly fires rounds and in which accuracy is of less concern, such as a military machine gun, superior gun performance is achieved by having the composite/metallic barrel wherein the coefficients of thermal expansion are contrasted so the composite restricts expansion of the metallic barrel and prevents bullets from excessive wobbling as they pass down the barrel. While other composite/metallic barrels may inadvertently constrict on the barrel, they do so unevenly, thereby increasing frictional wear by each bullet.
Summary of the Invention
Thus, it is an object of the present invention to provide a gun barrel made of metal and a composite wherein the gun barrel is formed to increase the useful firing life of the gun barrel.
It is an additional object of the present invention to provide a gun barrel for small arms which is lightweight and durable.
It is another object of the present invention to provide a gun barrel which is easy to make, easy to use and is inexpensive.
It is yet another object of the present invention to provide a composite/metallic gun barrel wherein the composite portion of the barrel is configured so as to prevent excessive expansion of the metallic liner when in the radial direction and have nearly 0 coefficient of thermal expansion in the axial direction.
The above and other objects of the invention are realized in a specific illustrated embodiment of a composite/metallic gun barrel having contrasting coefficients of thermal expansion in the radial direction. The gun barrel is made of a metal cylinder which is overwrapped with one or more composite layers. The composite layers are disposed about the metallic cylinder in such an arrangement that the coefficient of expansion for the composite material is selected and correlated relative to the coefficient of expansion for a preselected, preferred metal liner in the radial direction so as to restrict excess expansion of the liner in the radial direction, while having nearly 0 coefficient of thermal expansion in the axial direction. By evenly constricting the barrel liner, improved barrel performance is achieved. Thus, the composite material may be laid in such a manner that it restricts the expansion of the metallic cylinder under high use conditions in order to prevent premature wear or over expansion on the barrel due to friction with bullets fired therethrough. Adjustment of the coefficient of expansion in the radial direction of the composite allows selection of more favorable liner material, and offers enhanced ability to fine tune the cooperative relationship of the composite and the metal.
The exact disposition of the composite material, of course, depends both on the composite material and which metal is used for the metallic cylinder of the gun barrel. The composite and its expansion coefficient are correlated with the expansion coefficient of the metallic portion of the barrel in a winding pattern to give the composite an effective expansion coefficient which restricts the liner's expansion.
In accordance with the present invention, the gun barrel is coated with a bonding material and then overlaid with the composite material in a winding pattern configured to give the composite material an effective expansion coefficient, which is substantially dissimilar to that of the barrel so as to restrict radial expansion of the barrel, while maintaining nearly 0 coefficient of thermal expansion in the axial direction.
In accordance with another aspect of the invention, the composite material is wound onto a mandrel in a pattern to give it a predetermined coefficient of expansion and then cured. The composite portion of the barrel is then removed from the mandrel and mounted about a metallic portion of the barrel which has a coefficient of expansion which, when compared with that of the composite portion of the barrel, provides a desired barrel expansion characteristic. The composite/metallic barrel is then mounted to the stock of a gun.
In a presently preferred embodiment of the invention, the composite portion of the gun barrel is formed of alternating layers of composite material wherein one layer is hoop or spiral wound so that the fibers are generally disposed at about a 90 degree angle (.+-.10 degrees) to the long axis of the liner. The next most adjacent layer is overlaid on the hoop/spiral wound layer in a longitudinal placement. Additional layers of composite material disposed in longitudinal orientation may be laid prior to the next hoop/spiral wound layer. Typically, the ratio of longitudinal fibers to hoop wound (transverse) fibers will be less than 8:1. As the ratio of axial to hoop decreases, the composite casing limits the amount the metal liner can grow due to radial heat expansion.
Brief Description of the Drawings
The above and other objects, features and advantages of the invention will become apparent from a consideration of the following detailed description presented in connection with the accompanying drawings in which:
FIG. 1 shows a fragmented, side cross-sectional view of a gun barrel having a composite portion and a metallic portion made in accordance with the principles of the present invention;
FIG. 2 shows an exploded view of the gun barrel shown in FIG. 1;
FIG. 3 shows a graph of the coefficient of thermal expansion in longitudinal and transverse directions relative to the angle of winding; and
FIG. 4 shows a graph of longitudinal and transverse coefficients of thermal expansion as a function of the amount material placed longitudinally along the barrel versus the amount of material hoop or spiral wound about the barrel at an angle approximately 90 degrees to the long axis of the barrel .
Detailed Description
Reference will now be made to the drawings in which the various elements of the present invention will be given numeral designations and in which the invention will be discussed so as to enable one skilled in the art to make and use the invention. It is to be understood the embodiments discussed below are exemplary of the principles of the present invention, and are not intended to limit the invention as claimed.
Referring to FIG. 1, there is shown a fragmented, side cross-sectional view of a composite/metallic gun barrel, generally indicated at 8, made in accordance with the principles of the present invention. The gun barrel 8 includes a metallic liner 12, which is most typically made of stainless steel. A stainless steal metallic liner 12 is preferred because it is generally less prone to corrosion than other metallic liners.
The metallic liner 12 has a first section 12a which is configured to hold a round of ammunition in a chamber 16 formed by the liner, and an elongate second section 12b which extends substantially all of the remaining length of the barrel 8. The first end 12a is generally thicker than the elongate second section to help withstand the explosive force generated when firing a round of ammunition positioned in the chamber 16. In contrast, the second section 12b is thin so as to keep weight of the barrel 8 to a minimum. The primary purpose of the second, elongate section is to channel the hot, explosive gasses generated by firing the round of ammunition out of the barrel.
A casing 20 made of composite material is wrapped about the metallic liner 12. The casing 20 provides strength to the metallic liner 12, but requires less weight than conventional metal barrels. Thus, a barrel 8 which is stronger and lighter than conventional metallic barrels can be made by combining the metallic liner 12 and the composite casing 20. The metallic liner 12 is necessary to shield the composite casing 20 from the hot gasses generated when firing rounds of ammunition. These gasses are typically very corrosive to the composite casing 20 and can lead to premature failure if some sort of shielding is not provided.
The composite casing 20 will typically be made of graphite fibers which are coated with an epoxy material. For convenience, graphite "prepreg" will typically be used. Graphite prepreg is material which has been preimpregnated with an epoxy resin. Such a material can come in sheets which are easier to handle than individual graphite fibers.
As will be discussed in detail below, graphite is the preferred material for the composite casing because of its behavior when heated. Unlike most materials which expand under high heat conditions, graphite actually contracts longitudinally. By selectively controlling the contraction of the graphite, gun barrels 8 can be manufactured which have expansion characteristics which are particularly suited for high volume firing.
The composite casing 20 has a first section 20a which is disposed adjacent the first section 12a of the metallic liner 12a, and a second section 20b adjacent the second section 12b of the metallic liner. To maintain a generally continuous size for the barrel 8 and to ensure sufficient strength along the entire barrel, the first section 20a of the casing 20 is thin, tapering inverse to a taper of the first section 12a of the metallic liner 12, and the second section is thick so as to provide strength along the elongate second section 12b of the liner.
At the exterior of the metallic liner 12 and the interior of the composite casing 20 is an annular interface 24. This interface may be bonded with epoxy or other adhesives. This may be done regardless of whether the composite casing 20 is formed on a mandrel, cured and then placed on the metallic liner 12, or the composite casing 20 is formed about and cured on the liner. Both of these approaches to forming composite/metallic gun barrels 8 will be well known to those skilled in the art.
In addition to the above, the interface 24 between the composite casing 20 and the metallic liner 12 may be substantially nonbonded. The advantages and method for forming a substantially nonbonded composite/metallic gun barrel are discussed in detail in U.S. Ser. No. 08/574,402, pending, filed Dec. 18, 1995.
Disposed about an outer circumference of the composite casing 20 of the gun barrel 8 is an overwrap 28. The overwrap 28 may be a series of helically wound fibers, or preferentially, a knitted or woven cloth made of graphite fibers.
Referring now to FIG. 2, there is shown an exploded view of the gun barrel 8 as shown in FIG. 1. The gun barrel 8 includes the metallic liner 12, having the first and second sections, 12a and 12b, respectively, and the composite casing 20, which includes a plurality of graphite fibers, generally indicated at 32.
The graphite fibers 32 are generally disposed about the metallic liner in first and second groups of fibers 36 and 40, respectively, which are characterized by their orientation. The first group 36 of fibers is disposed in a first orientation so as to circumscribe the metallic liner 12. This may be accomplished by cutting a sheet of prepreg graphite fibers and wrapping the sheet about the metallic liner 12 so that the fibers form a plurality of hoops disposed at about 90 degree angle to a long axis A--A of the metallic liner. In the alternative, the first layer 36 may be formed from a single graphite fiber which is wrapped in a tight spiral so that the fiber is continuously disposed at about 89 degrees from the long axis A--A. Those skilled in the art will appreciate that other angles can be used, preferably those within .+-.10 degrees of 90 degrees for the radially wound fibers and within .+-.10 degrees of the long axis for the longitudinally placed fibers. Thus, when used herein, "hoop winding" or "substantially perpendicular" to the long axis and "generally perpendicular" are intended to include the above identified range for the radially wound fibers. Likewise, "substantially longitudinally" and "generally parallel" to the long axis are intended to cover the above identified range of the longitudinally placed fibers.
In a preferred embodiment, the metallic barrel liner 12 is first wrapped with a fiberglass scrim cloth 34 coated with epoxy or resin. The scrim cloth 34 acts as an insulator to prevent corrosion between the electrically conductive metallic liner 12 and the electrically conductive graphite portion of the barrel casing 20.
Disposed on the first group 36 of fibers is the second group 40 of fibers which consists of elongate graphite fibers which are disposed parallel to the long axis A--A of the metallic liner. The elongate fibers of the second group 40 are disposed in a second orientation wherein the fibers are laid side to side about the circumference of the metallic liner 12 so as to form at least one generally continuous layer. Additional layers of fiber may be laid in the second orientation before another first group 36 of fibers are positioned about the second group 40 in the first orientation.
By varying the number of layers in the second group 40 of fibers with respect to each group of fibers disposed in the first orientation, the coefficient of thermal expansion for the composite casing 30 can be regulated to provide desired expansion characteristics. For example, in FIG. 1, the metallic liner 12 is wrapped by a first group 36 forming a single first layer. A single layer disposed in the second orientation to form the second group 40 are then overwrapped on the first layer 36. Another first group of fibers 36 disposed in the first orientation is placed about the second group 40, followed by another single layer forming another second group 48 of fibers. This alternating arrangement is repeated multiple times at any point along the metallic liner 12.
The one to one (or two to one as shown at 40a) wrapping of the layers of the second group 40 relative to first group 36 provides a composite casing 20 which has expansion coefficients which is smaller than those of a stainless steel liner in the radial direction and has nominal or nearly 0 coefficient of thermal expansion in the axial direction. By forming a composite casing 20 with a consistently smaller expansion coefficient than that of the metallic liner 12 in the radial direction and maintaining nearly 0 coefficient of thermal expansion in the axial direction, the barrel is constricted and is not as prone to erosion during rapid fire situations. Such constriction between the composite casing 20 and the metallic liner are best achieved in graphite when using less than 2 layers in the second orientation for every layer in the first orientation. It is preferable to have about even amounts of fiber by weight disposed in the first and second orientations.
Those familiar with rapid firing guns, such as those commonly referred to as machine guns or automatics, will appreciate that a major concern is the speed with which the barrels deteriorate. When the gun is fired at a high rate, the heat in the barrel causes the metal to expand. The expanded metal allows a bullet passing through the barrel 8 to wobble or bounce from side to side within the barrel as it is propelled forward. Such movement by the bullet substantially increases friction within the barrel and causes the barrel to wear more rapidly and unevenly, defeating accuracy of flight.
By restricting the expansion of the metallic liner 12, a substantial amount of the increase in friction caused by rapid firing can be eliminated. While limiting expansion of the metallic liner 12 affects accuracy, typically due to uneven binding which causes slight warpage in the liner, such restrictive design does provide a countervailing benefit. As the bullet travels down the barrel, it is more likely to spin properly and avoid the friction increasing wobble common in the prior art. The constriction of the metallic liner 12 also has the positive effect of increasing barrel life, due to a decrease in friction. Thus, for rapid fire guns, a composite/metallic gun barrel 8 made in accordance with the principles of the present invention can be made lighter, stronger and longer lasting than those of the prior art while maintaining similar accuracy.
Referring now to FIG. 3, there is shown a graph of the coefficient of thermal expansion in longitudinal (axial) and transverse (radial) directions relative to the angle of winding. The graph includes a first, dashed curve 50 which shows that when the fibers are disposed longitudinally along the metallic lining, i.e. 0 degrees from the long axis of the metallic liner 14 (FIG. 2), the longitudinal coefficient of expansion for the fibers is slightly less than zero. In such a position, however, the transverse coefficient of expansion is almost 0.00002, as represented by curve 54. As the lay-up angle of the fibers is changed from 0 degrees to 90 degrees, the longitudinal coefficient of expansion changes from a slight negative to slightly less than +0.00002. The transverse coefficient of expansion, in contrast, decreases from nearly 0.00002 to slightly less than zero.
In the center of the two extremes, the two curves cross at a lay-up angle of approximately 45 degrees. In such a position, the composite casing 20 (FIGS. 1 and 2) of the gun barrel 8 (FIGS. 1 and 2) will expand in both longitudinal (axial) and transverse (radial) directions. This is a common lay-up angle used in the prior art. Unfortunately, such a lay-up angle lacks the similar expansion of the metallic liner 12 (FIGS. 1 and 2) available with the perpendicular placement discussed above. The 45 degree lay-up angle lacks the benefits of a 1:1 longitudinal to hoop ratio in the composite casing which sufficiently restricts expansion of the metallic liner without substantial axial expansion.
FIG. 4 shows another graph in which the longitudinal coefficient of thermal expansion is shown relative to the percentage of transverse layers (90 degrees) relative to longitudinal layers (0 degrees). Beginning at the left of FIG. 4, there is shown a curve 60 representing the transverse coefficient of thermal expansion for the composite casing 20 (FIGS. 1 and 2). When the casing 20 has little or no fibers which are hoop or spiral wound at an angle close to 90 degrees, the casing has a transverse coefficient of thermal expansion of nearly 0.00002 in/in/.degree.F. With approximately 10 percent fibers wound at approximately 90 degrees, the transverse coefficient of thermal expansion is about 0.000006 in/in/.degree.F., the same coefficient of expansion as stainless steel, such as that which would be used in the metallic liner 12 of a gun barrel 8.
As the percentage of fibers which are wound at 90 degrees approaches 100 percent, the transverse coefficient of thermal expansion falls to slightly below zero. At such a level, the fibers would actually constrict against a metallic liner which had not expanded. By using a 1:1 ratio, constriction is reserved for significant expansion.
At the right of FIG. 4, a dashed curve representing the longitudinal coefficient of thermal expansion is indicated at 70. When the fibers of the composite casing 20 (FIGS. 1 and 2) are nearly 100 percent disposed in a 90 degree orientation, the longitudinal coefficient of thermal expansion is between 0.00001 and 0.00002. As the percentage of fibers wound at 90 degrees falls, the longitudinal coefficient of expansion decreases. When all of the fibers in the casing 20 are disposed along the long axis of the metallic liner, the longitudinal coefficient of thermal expansion is slightly less than zero.
The curve 60 representative of the transverse coefficient of thermal expansion and the curve 70 representative of the longitudinal coefficient of thermal expansion intersect at a point where the casing is formed of an equal amount of fibers disposed in the first orientation (90 degrees) and fibers disposed in the second orientation (0 degrees), as indicated by point 80. In such a balance, the composite casing allows some expansion of the metallic liner, but provides better constriction than a 45 degree lay-up angle as is shown in FIG. 3. Also, the 0/90 lay-up is much stronger in the radial and axial directions than the .+-.45.degree. winding.
If a liner other than stainless steel is desired to be used, the ratio of layers in the second orientation relative to the first orientation need only be modified to create a casing which constricts the expansion a desired amount. Thus, for example, if a liner was chosen which had a transverse thermal expansion of 0.000008, the percentage of fibers in the first orientation (90 degrees would be reduced. Typically, the casing would have one layer in the first orientation and then thirteen or fourteen layers in the second orientation, repeated several times.
Thus, there is disclosed composite/metallic gun barrel having coefficients of thermal expansion which are correlated to the particular purpose of the gun. If the desired product will be used for rapid firing, only about one second layer is used for each first layer, thereby causing the casing to restrict transverse expansion of the liner. Thus the present application teaches a method for reducing barrel weight in a firearm, while at the same time enhancing predictability in barrel performance despite changing temperatures during firing. The method involves forming a barrel with a metallic liner having an exterior surface and an interior surface configured for firing a projectile and applying multiple layers of reinforcing fiber in predetermined orientations along the exterior surface of the metallic liner in combination with thermosetting resin. The casing formed by curing the material has a substantially zero coefficient of expansion in an axial direction of the barrel in the composite in response to changes from ambient temperature due to heating of the barrel during firing of the firearm. Most importantly, the casing also has a coefficient of expansion in the radial direction which is less than that of the liner to minimize expansion of the metallic liner by limited expansion by the composite.
In light of the above disclosure, those skilled in the art will recognize numerous modifications which can be made without departing from the scope and spirit of the present invention. The appended claims are intended to cover such modifications.
Claims
What is claimed is:
1. A method for reducing barrel weight in a firearm, while at the same time enhancing predictability in barrel performance despite changing temperatures during firing, said method comprising: a) forming a barrel with a metallic liner having an exterior surface and an interior surface configured for firing a projectile, the metallic liner having a known coefficient of thermal expansion in an axial direction and in a radial direction; b) applying multiple layers of reinforcing fiber in predetermined orientations along the exterior surface of the metallic liner in combination with thermosetting resin to form a surrounding composite shell which, subsequent to cure, develops: i) a substantially zero coefficient of expansion in the axial direction of the barrel in the composite in response to changes from ambient temperature due to heating of the barrel during firing of the firearm; and ii) a coefficient of expansion in the radial direction which is sufficiently less than the coefficient of thermal expansion of the metallic liner in the radial direction to impose a restrictive force on expansion of the metallic liner in the radial direction by lesser expansion by the composite; and c) curing said composite to a final condition wherein thermal elongation changes in the barrel are uniform along axial and radial aspects of the barrel.
2. The method of claim 1, wherein the gun barrel liner has a long axis, and wherein step (b) comprises, more specifically, positioning at least half of the fibers (by weight) generally parallel to the long axis of the liner.
3. The method of claim 2, wherein a majority of fibers not disposed generally parallel to the long axis of the liner are disposed generally perpendicular to the long axis of the liner.
4. The method of claim 3, wherein the amount of fiber disposed generally parallel to the long axis of the liner is in a ratio of less than 4:1 with the amount of fiber disposed generally perpendicular to the long axis of the liner.
5. The method of claim 4, wherein the amount of fiber disposed generally parallel to the long axis of the liner is about the same as the amount of fiber disposed generally perpendicular to the long axis of the liner.
6. A method for forming a composite/metallic gun barrel with a desired coefficient of thermal expansion, the method comprising: (a) selecting a metallic liner having a long axis and a known coefficient of thermal expansion in radial and axial directions; (b) disposing a first group of fibers about the metallic liner in a first orientation at an angle generally perpendicular to the long axis of the liner; and (c) disposing a second group of fibers about the metallic liner in a second orientation generally parallel to the long axis of the liner, the first and second groups forming a composite casing, wherein the amount and orientation of fibers in the first group relative to the amount and orientation of fibers in the second group are coordinated to form the composite casing having a coefficient of thermal expansion in the radial direction with is sufficiently less than the coefficient of thermal expansion of the liner in the radial direction, the composite casing having a nominal coefficient of thermal expansion in the axial direction to impose a restrictive force with respect to radial expansion of the liner.
7. The method according to claim 6, wherein step (c) comprises, more specifically, forming the second group of fibers from sufficiently few number of second layers about the first layer that the resulting composite casing has a coefficient of thermal expansion in the radial direction which is less than the coefficient of thermal expansion in the radial direction of the metallic liner.
8. The method according to claim 6, wherein step (a) comprises, more specifically, choosing a stainless steel liner, and wherein steps (b) and (c) comprise, more specifically, disposing the first and second groups of fibers in alternating layers, the layers formed from the second group of fibers having between about one and two times the amount of fiber in each layer as the amount of fiber in each layer formed by the first group of fibers.
9. The method according to claim 8, wherein the composite casing is by wrapping graphite fibers coated with epoxy about the metallic liner and curing the fibers.
10. The method according to claim 6, wherein steps (b) and (c) comprise, more specifically, wrapping graphite fibers coated with epoxy about a mandrel; curing the fibers and epoxy so as to form a hardened casing; removing casing from the mandrel; and disposing the hardened casing about the metallic liner.
11. The method according to claim 6, wherein the method further comprises placing an insulative layer about the metallic liner before performing step (b).
12. The method according to claim 11, wherein step (a) comprises, more specifically, selecting a metallic liner having a long axis and wrapping the liner in a fiberglass cloth coated with epoxy.
13. A composite/metallic gun barrel comprising: a metallic liner having a long axis and a coefficient of thermal expansion in the radial direction; a first group of graphite fibers disposed about the metallic liner in a first orientation generally perpendicular to the long axis of the metallic liner; and a second group of graphite fibers disposed about the metallic liner and the first layer, each of the fibers in the second group being disposed in a second orientation generally parallel with the long axis of the metallic liner, the amount of fibers being disposed in the second orientation being not more than the amount of fibers disposed in the first orientation; and wherein the first and second groups of fibers form a composite casing having (i) a coefficient of thermal expansion in the radial direction less than the coefficient of thermal expansion in the radial direction of the metallic liner, so as to limit expansion of the liner when the liner and casing are heated, and (ii) a nominal coefficient of thermal expansion in an axial direction.
14. The composite/metallic gun barrel of claim 13, wherein the gun barrel comprises a plurality of layers formed alternatingly from fibers of the first group and fibers of the second, each layer containing fibers from the first group being disposed adjacent a layer containing fibers of the second group.
15. The composite/metallic gun barrel of claim 13, wherein each layer comprising fibers from the second group of fibers has between about 1 and 2 times the amount of fibers (by weight) as the layers comprising fibers from the first group of fibers.
16. The composite/metallic gun barrel of claim 15, wherein each layer comprising fibers from the first group of fibers comprises a single layer of fibers.
17. The composite metallic gun barrel of claim 16, wherein the metallic liner comprises stainless steel.
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