System and method for improving performance of a weapon barrel

[0001] This application claims priority to U.S. Provisional Patent Application Ser. No. 61/161,370 filed Mar. 18, 2009, titled “Improved Sniper Rifle”, the contents of which are incorporated by reference herein.

[0002] Sniper rifles and other high accuracy guns and artillery are designed to repeatedly deliver a projectile accurately and precisely. However, it will be appreciated that variations within the barrel, including perturbations caused by acoustic disturbances produced through the act of firing, can cause important changes to the trajectory or flight path of a projectile, thereby causing a decrease in accuracy. Currently, methods for reducing such perturbations typically relate to devices operable to mechanically balance a muzzle at the point where the bullet exits the barrel, such as those discussed in U.S. Pat. No. 5,794,374, or the use of movable counterweights such as those marketed under the mark Limbsaver®. Other methods for reducing such perturbations include U.S. Pat. No. 6,889,462 that utilize a leaf spring system for compressing a barrel until its “sweet spot” is found can reduce variability in the accuracy of a weapon barrel. However, it would be appreciated in the art to supply a system and method for reducing the variability induced in a barrel through acoustic disturbances without the need to iteratively tension and/or counterbalance followed by field testing the proper spring loading or counterweight position for each individual barrel and ammunition type.

[0020] According to at least one additional embodiment, a harmonic barrel dampener is utilized. Turning now to FIGS. 1A and 1B, a harmonic barrel dampener 20 comprises an outer portion 22 that substantially encases or enwraps a significant portion of barrel 30, and optionally includes within its lumen an elastomeric or acoustic dampening material 40 to encase or substantially enwrap a substantial portion of the length of the barrel. In operation, any acoustic dampening material 40 at least partially fills the lumen of the harmonic barrel dampener 20 between the outer portion 22 and the exterior 32 of barrel 30.

[0021] According to at least one exemplary embodiment, acoustic dampening material 40 comprises a polymeric compound having the ability to dampen acoustic, vibrational, and/or heat anomalies of barrel 30 under normal operating conditions of a weapon. In at least one exemplary embodiment, a hollow tube comprising a metal, alloy, polymer, composite, fiberglass, and/or carbon fiber is selected such that the diameter of the hollow tube is large enough to encase barrel 30 along its length from approximately the distal end of the bullet chamber 50 to a point near the exit point of the barrel 55. By way of nonlimiting example, it will be appreciated that FIGS. 1A and 1B portray a 1.5 inch diameter aluminum tube as outer portion 22 of harmonic barrel dampener 20, as placed on a straight-pull action rifle, with harmonic barrel dampener 20 running approximately from the interface of the barrel 30 and rifle action 100.

[0022] In at least one embodiment, elastomeric or acoustic dampening material 40 comprises a polysulfide elastomeric material which retains elastomeric properties over a range of temperatures of at least −40° F. to 250° F., similar to that utilized for o-ring production on the space shuttle engines. According to at least one additional example, the elastomeric material retains elastomeric properties over a range of temperatures of between 0° C. and 100° C. For example, a two component chemically cured polysulfide sealant such as “Product 964” sold by Epoxy.com a Division of Epoxy Systems, Inc., 20774 W. Pennsylvania Ave., Dunnellon, Fla. 34431 may be used as the elastomeric or acoustic dampening material 40. In at least one embodiment, the two part polysulfide was poured into the hollow tube surrounding a rifle barrel, and allowed to cure until fully polymerized. Optionally, a retainer ring may be utilized to compress the hollow tube against the receiver of the rifle during curing of the two part polysulfide used as an elastomeric or acoustic dampening material 40, and may be used to compress the rifle barrel before and/or after the curing process to further reduce vibration.

[0023] Optionally, according to at least one other embodiment, a member operable to diffuse heat build-up between barrel 30 and elastomeric or acoustic dampening material 40 may be utilized. For example, a heat conducting material such as a metal mesh, ceramic matrix, carbon nano-tubes or other heat conductive component may be utilized at or near the interface between the elastomeric or acoustic dampening material 40 and exterior 32 of barrel 30. Further optionally, the heat conducting material may be attached to a heat sink or other heat-dissipating device.

[0024] According to at least one additional embodiment, the hollow tube or other device utilized to maintain the elastomeric or acoustic dampening material 40 around barrel 30 during the curing process may optionally be removed after the curing process, resulting in a harmonic barrel dampener that does not include an outer wall 22.

[0025] By way of nonlimiting examples, a Thompson Encore 1Z rifle, Springfield 1903A2 rifle and a Swiss K31 rifle were each retrofitted with a harmonic barrel dampener 20 according to at least one embodiment discussed above. Match ammunition designed for exceptional consistency and symmetry in combination with precisely weighed propellant powders assembled by repeatable methods with little variation were used to test each rifle, in both the unmodified and modified form. A variety of hand load Match ammunitions were used as specified for the given rifle, which included: Hornady 40 grain VMAX bullets of 0.223″ diameter at approximately 3350 feet per second, Hornady 55 grain VMAX bullets of 0.223″ diameter at 3280 feet per second, Sierra Match King 52 grain hollow point boat tail bullets of 0.223″ diameter at velocities of 2900 to 3400 feet per second, and Hornady 168 grain hollow point boat tail match bullets of 0.308″ diameter at velocities of 2400 to 2700 feet per second, and Swiss military surplus 172 grain full metal jacket bullets of 295″ diameter at approximately 2570 feet per second, and was fired by a marksman at 100+/−1 yards. Example targets from each rifle from before and after the addition of the harmonic barrel dampener are included as FIGS. 3A, 4A, 5A, 6A, 7A, and 8A, with the results discussed in further detail below.

[0026] Turning now to FIGS. 3A-B and 4A-B, a Thompson Encore® rifle was used to fire many shots at targets 100 yards from the rifle using Hornady 40 grain Match bullets in the unmodified rifle. FIGS. 3A-B show an exemplary result from the test firing prior to adding the harmonic barrel dampener 20. FIGS. 4A-B display an exemplary result after a four shot session at 100 yards, using the same ammunition but modified with the harmonic barrel dampener 2.

[0027] Turning now to FIGS. 5A-B and 6A-B, for the same Thompson Encore® rifle in its unmodified state but shooting Hornady 55 grain VMAX bullets, a representative target is shown in FIG. 5A. However, the same rifle, modified with the harmonic barrel dampener and shooting the same match ammunition delivers the representative target shown at FIG. 6A.

[0028] A similar comparison is shown in FIGS. 7A-B and 8A-B for a 1903A3 Springfield rifle both examples of which are using Hornady 168 grain hollow point boat tail bullets. The representative target at FIG. 7A is of the rifle before modification while the target shown at FIG. 8A shows the improved repeatability and accuracy after the rifle has been improved by the addition of a harmonic barrel dampener 20.

[0029] In yet another embodiment, the scatter plots shown in FIGS. 9 and 10 aggregate several data points together, with FIG. 9 detailing the aggregated shots of an unmodified Swiss K31 rifle, while FIG. 10 aggregates shots using the same 172 grain surplus ammunition in the same rifle after the addition of a harmonic barrel dampener 20 according to at least one of the embodiments discussed above.

Summary of Exemplary Results

[0030] Table 1 below records and typifies the results across multiple rifles and multiple calibers all demonstrating significant improvements in accuracy and repeatability after the addition of the harmonic barrel dampener. The primary measure of improvement is based on a United States military standard of accuracy called the “mean radial dispersion.” This measure is the average of each shot's distance from the virtual center of a target as defined by the shots made at the target, and is shown for each rifle before and after the addition of the harmonic barrel dampener 20. It should be noted mean radial dispersions of 1″ to 1.5″ are considered good for most military grade small bore weapons. Additionally, the Kolmogorov-Smirnov statistical test {which functions for samples taken from any continuous distribution function) applied here is a robust test of independence between the accuracy of the unmodified and stabilized rifles. The application of this test provides the probability the improved performance is real and not simply a unique random selection of the same distribution.

[0031]

TABLE 1
			sample	mean radial		Kolmogorov-
			size	disperson		Smirnov
prototype	test condition	ammunition	(rounds)	(inches)	σ	Test1
Thompson Encore	bare barrel	Hornady 40grain	19	0.37	0.18	D = 0.35
Thompson Encore	dampend	VMAX	18	0.27	0.13
	barrel	Hornady 40grain
		VMAX
		difference/		27%	28%	85%
		improvement
Thompson Encore	bare barrel	VMAX 55grain	19	0.68	0.27	D = 0.61
Thompson Encore	dampend	VMAX 55grain	17	0.37	0.19
	barrel
		difference/		46%	30%	100%
		improvement
Springfield		168 grain Match	28	0.60	0.22	D = 0.76
1903A3		168 grain Match	15	0.30	0.12
Springfield
1903A3
		difference/		49%	45%	100%
		improvement
K31 Swiss	bare barrel	168 grain Hornady	22	0.81	0.50	D = 0.50
K31 Swiss	dampend	168 grain Hornady	15	0.50	0.20
	barrel
		difference/		38%	60%	97%
		improvement
K31 Swiss	bare barrel	172 grain surplus	27	1.56	0.92	D = 0.91
K31 Swiss	dampend	172 grain surplus	15	0.47	0.16
	barrel
		difference/		70%	83%	100%
		improvement

[0032] In addition to the abovementioned improvements in accuracy, it should be noted that the addition of a harmonic barrel dampener according to at least one embodiment described above resulted in a significant reduction in the maximum external barrel temperature. In particular, the maximum external barrel temperature was reduced an average of 34%. This reduction will, at the very least, reduce the infrared signature of the weapon and increase the survivability of any soldier employing such an improvement on the firearm, and may ultimately help the variability of a rifle's aim-point which depends on the barrel temperature.

[0033] While specific embodiments have been disclosed herein, combinations of those embodiments, as well as certain variations thereof are included in the scope of this application. For instance, it is anticipated that a harmonic barrel dampener as disclosed herein will have similar results on other ballistic barrels beyond standard firearms. For example, tank and artillery barrels are anticipated to behave similarly and harmonic barrel dampeners are intended to encompass applications thereon.