Firearms – Implements – For launching grenades
Reexamination Certificate
2001-08-24
2003-07-15
Jordan, Charles T. (Department: 3641)
Firearms
Implements
For launching grenades
C042S017000
Reexamination Certificate
active
06591535
ABSTRACT:
BACKGROUND OF INVENTION
The present invention relates generally to firearms, and more particularly to firearms for firing grenades and other large projectiles. Some grenades are chemical, dispensing tear gas or nausea gas. Other grenades eject flares for signaling, marking rounds with smoke, phosphorous for lighting fires, and regular high explosive grenades for anti-personnel and anti-armor purposes.
The United States Army adopted the 40 mm M79 grenade launcher in the early 1960's to provide the infantryman with an effective area-fire fragmentation weapon having a much greater range than possible with hand thrown grenades. Despite its effectiveness, the M79 is a single shot weapon limited to a low rate of fire. This low fire rate of single shot weapons can be a serious handicap because the grenadier is effectively disarmed while reloading the grenade launcher, providing the enemy an opportunity to attack or maneuver before the grenadier can further engage him. A further disadvantage with the M79 is that the rifle firepower of the infantry unit is reduced by one rifle.
Experienced grenadiers often do not use the weapon sights to establish a firing angle for the grenade launcher, but rather fire a first round at an angle of elevation based on experience. The grenadier observes the impact of this ranging round to make any required adjustment in the aim of the weapon at the target. Even though this technique is widely employed, it suffers from a disadvantage as employed with a single shot grenade launcher. The grenadier must lower the weapon to reload. Without exercising considerable skill, the weapon cannot be returned closely to its previous firing position to make the desired aiming correction, thus reducing the accuracy of the next fired round. Even if the grenadier can bring the target area under accurate fire, the delay between the ranging round and each succeeding round increases the time available for the target to take cover.
In order to address some of the problems associated with single shot weapons, the M203 grenade launcher attachment was developed for the M16 rifle. While the M16/M203 system provides the grenadier with rifle fire power in addition to grenade launching capabilities, the accuracy and grenade firing rate is degraded as compared to the M79 grenade launcher because of the increased weight and bulk of the combination weapon. In addition, the effectiveness of the M16 rifle attached to the grenade launcher is reduced.
Self powered weapon operating systems are commonly classified according to how energy is extracted from the propellant gases to operate the weapon. These systems can be classified as gas systems, recoil systems, and various types of blowback systems. These systems extract energy from the propellant gas and convert this gas into kinetic energy, which is imparted to the moving parts of the operating system. Weapon operating systems may also be classified according to the relationship of their primary and secondary masses. In gas, recoil and retarded blowback operating systems, most of the kinetic energy of the system is stored in a primary mass, typically called the bolt carrier or operating rod. The kinetic energy of the primary mass provides the energy for unlocking the secondary mass, which is typically called the bolt. After unlocking the secondary mass, the primary mass picks up the secondary mass and the two masses continue to recoil as a unit. Straight blow back weapons utilize only a primary mass.
Gas operated systems for grenade launchers are ineffective due to the internal ballistic characteristics of grenade cartridges. Grenade cartridges generate very low chamber pressure and a short pressure pulse. When coupled with the high expansion ratio of the cartridge, little gas pressure remains for operating the weapon.
Recoil operation of a shoulder fired grenade launcher presents difficulties because of the mount sensitivity of recoil operated systems especially since there is a low ratio of weapon mass to projectile mass in grenade launchers. Straight blowback operation for shoulder fired grenade launchers also presents difficulties because bolt recoil velocities cannot be kept within manageable limits without employing unacceptably massive bolts for a shoulder fired weapon.
There are also disadvantages associated with conventional retarded blowback operation of grenade launchers. The energy available for transfer to the operating mechanism in a retarded blowback operating system, as in a recoil system, depends on limiting receiver movement during firing, which is governed by the mounting resistance of the weapon. Grenade projectiles are relatively heavy when compared to the shoulder weapons in which they are fired; thus, grenade launchers are more sensitive to mounting resistance than are service rifles and machine guns. For example the M16 rifle weight to projectile weight ratio is about 800:1, and the M60 machinegun weight to projectile weight ratio is about 1000:1. In contrast, if a grenade launcher weighs 5 pounds, then the weapon to projectile weight ratio for a standard 40 mm grenade is about 13:1. This very low ratio associated with the grenade launcher is not conducive to reliable functioning in a conventional retarded blowback operating system. This is because the mounting resistance will vary greatly depending on whether the grenade launcher is held firmly against the shooter's body or away from the shooter's body, as well as the number of cartridges remaining in the magazine. If the receiver moves too far, then the receiver absorbs too much energy, thus reducing the energy available for driving the operating mechanism.
Multiple shot semi-automatic grenade launchers also have problems that relate to the recoil springs of the weapon. Conventional compression springs in weapon operating systems are limited to about 40 fps loading velocity; beyond which springs suffer from destructive spring surge. Therefore, the initial velocity of the bolt carrier must not exceed 40 fps.
A shoulder fired grenade launcher requires a relatively strong recoil spring to reliably chamber cartridges since the weapon is fired at high elevation angles and since the masses of a conventional bolt and of grenade cartridges are relatively large. This results in another problem associated with conventional box magazines relative to cartridge feeding and chambering grenade cartridges. A long overtravel for the bolt behind the top cartridge in the magazine is necessary to provide adequate time for the magazine follower spring to lift the cartridge stack to position another cartridge for chambering by the bolt. A relatively strong magazine follower spring must also be provided for adequate cartridge feeding. Additionally, a long chambering ramp is necessary which requires a long bolt travel, in spite of the next grenade cartridge typically being positioned as close as possible to the bore axis. Increasing the strength of the magazine follower spring causes the next cartridge in the magazine to exert a greater frictional or braking effect on the recoiling parts. Such compromises in the design of multiple shot grenade launchers using conventional magazines result in marginal reliability in cartridge feeding.
The relatively large mass of a grenade cartridge creates additional problems. An example of a multiple shot grenade launcher with a three chambered design is provided in U.S. Pat. No. 5,052,144. The grenade launcher of the '144 patent includes a sliding horizontal magazine serving as a firing chamber that aligns each cartridge to be fired with the barrel. Since this magazine is displaced off-axis relative to the bore, the center of gravity of the magazine changes with each shot, causing the grenade launcher to recoil about a different center of gravity. The magazine described in the '144 patent thus creates a different horizontal angle of departure for each shot relative to the line of sight, thus altering the point of impact of each projectile in azimuth.
While there have been attempts in the prior art to provide multiple shot grena
Armalite Inc.
Buckley Denise J
Jordan Charles T.
Woodard Emhardt Moriarty McNett & Henry LLP
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