In order to meet the needs of the modern battlefield, the infantry detachment urgently needs a heavy machine gun that can follow the maneuver and has powerful firepower to deal with targets such as armored vehicles, wheeled vehicles and armed vehicles. However, the traditional 7The 62 mm caliber heavy machine gun has a short firing range, weak power, and poor anti-aircraft capabilities, which makes it difficult to meet the requirements of combat, and 12The 7 mm caliber anti-aircraft machine gun was too heavy, inconvenient to carry, and easy to expose. In response to this problem, after more than 10 years of research, China's leading experts have successfully developed the world's most "light" large-caliber heavy machine gun - *Z89 Type 127 mm heavy machine gun. The system is composed of heavy machine guns, white light sights, low-light sights, armor-piercing incendiary shells, shell-piercing armor-piercing shells, armor-piercing incendiary tracer bullets, gun mounts and other parts, mainly used for flat fire, striking at medium and long-distance living targets, military equipment, light fire points, light armored targets or bunkers, and if necessary, it can also shoot at low-flying armed targets.
*Z89 Formula 12The 7mm heavy machine gun uses a number of innovative designs that make it one of the best in the world. First, for the first time, the barrel short recoil-gas conduction hybrid automatic method was adopted on the large-caliber machine gun, which effectively reduced the recoil force of gunpowder gas on the gun body, which was conducive to reducing the weight and improving the shooting accuracy. Second, for the first time, the annular lever transmission mechanism is used in the bomb supply system, so that the structure is simple, compact, concealed and stable. Third, for the first time, the cradle and bracket integrated gun carriage are adopted, and the upper and lower frames are connected by spherical hinges to realize the simultaneous tightening of the high and low machine and the direction machine, with simple structure and easy to use. Fourth, for the first time, new materials and new processes are widely used in large-caliber machine guns, such as the receiver body, the shell cover body, the launch base, the loading handle slide plate, the rotating body seat on the gun carriage, the upper and lower hoops, etc., using aluminum alloy materials and advanced hot die forging technology, which not only effectively reduces the weight of the first class, but also enhances the wear resistance. China's self-developed **Z89 type 12The success of the 7 mm heavy machine gun demonstrates the high level of development of light light in our country, even compared with famous guns of the same type in the world, it does not fall behind.
It has the characteristics of light weight, fast rate of fire, strong firepower, long range, great power, easy maneuverability, and all-weather use, and has been welcomed and praised by the troops. However, after many years of use by the army and the teaching practice of academies, some problems have also been discovered: First, the accuracy of continuous firing is not high and the accuracy has decreased; second, the failure rate increases; Third, the function is not perfect enough and needs to be further improved. This paper conducts an in-depth study of these problems, analyzes the causes of their occurrence, and proposes ways to improve them.
Burst firing accuracy is an important indicator of the tactical performance of heavy machine guns, and in combat training, burst firing is a common shooting method for heavy machine guns. **The Z89 heavy machine gun has low continuous firing accuracy and large projectile dispersion due to the following two aspects: First, the gun carriage is light in weight and has large elastic deformation. The gun adopts an elastic gun mount, when firing, the gun carriage is stressed, so that the axis of the gun body produces an angle, and when the second round is fired, the gun body has not fully recovered to the angle of fire when firing, thereby reducing the accuracy of continuous firing. Second, there is a large gap between the barrel and the receiver. The structure of the gun adopts the connection mode of the guide edge of the barrel connecting seat and the guide groove of the receiver connector. When firing, the reciprocating motion of the guide edge relative to the guide groove produces violent friction, coupled with the operation of the barrel decomposition and combination, the gap between the guide edge and the guide groove increases, and finally leads to the radial loosening of the barrel on the receiver, which not only changes the aiming line of the starting position, but also increases the dispersion of spot and burst fire, and also affects the accuracy of single shot.
Improvement measures: First, improve the structural rigidity of the gun carriage. By changing the structural parameters of the gun frame rod, such as the length, wall thickness, cross-sectional width and height of the frame rod, etc., the natural vibration frequency is changed, and then the matching relationship between the stable radio frequency of the gun frame and the natural vibration frequency of the structure is adjusted, and the dynamic stability of the gun frame is increased. The second is to optimize the connection structure between the barrel and the receiver. Rigid wear-resistant materials are embedded in the receiver to increase wear resistance and matching, and improve the accuracy of burst fire. The first that has been installed is repaired by ceramic composite plating process, and at the fit between the guide edge of the barrel connecting seat and the guide groove of the receiver connector, ceramic composite coating is used to eliminate the gap, improve the shooting accuracy and increase wear resistance, and prolong the service life.
The reasons for the decline in accuracy are as follows: First, the cover of the bomb-receiving machine is too loose. Due to the repeated operation during training and the vibration and collision during shooting, the gap between the connection between the bomb-receiving cover and the receiver increased, resulting in the loosening of the bomb-receiving cover after it was closed. The ruler base is fixed at the back and top of the bomb-receiving machine cover, and the bullet-bearing machine cover will also produce a loosening phenomenon after opening and closing many times, resulting in the loosening of the gauge (light door), changing the aiming line of the starting position, and directly affecting the aiming accuracy.
Second, the tightening deviation of the gun body is large. Under the action of the thread, the right side of the connector clamps the spherical shaft downward, and the connector drives the receiver to tilt to the right, and the front sight is offset to the right. According to the measurement, the right side of the connecting body is tilted downward by about 1 mm, resulting in aiming error, which directly affects the shooting accuracy. The third is that the looseness of the casing on the connecting seat is too large. Due to the wear of the joint between the clamping sleeve of the gun body and the receiver, or the wearing of the positioning gap between the two positioning pieces on the inner side of the connecting seat and the positioning gap on both sides of the receiver, the gap gradually increases, and the receiver moves back and forth or loosens left and right in the connecting seat.
Improvement measures: First, improve the fixed position of the ruler base, and fix the ruler directly on the receiver. 67-2 Formula 762-mm heavy machine gun and Type 85 Type 12The 7mm anti-aircraft machine guns and other equipment are fixed to the receiver, which effectively avoids the accuracy of aiming due to the loosening of the shell cover. The second is to embed a rigid wear-resistant liner in the wear-prone parts or adopt a ceramic composite coating process to increase wear resistance, improve the reliability of the combination, and then improve the shooting accuracy.
In use, the increase in the failure rate and the decrease in reliability are the main problems of the gun, and the main failures that often occur are: the slide (when the trigger is released, the shooting should be stopped. In the event of a slip failure, the shooting will not stop until the bullet on the chain is finished), the shell will not be withdrawn, and some parts are easy to break.
The reason for the failure of the slip machine and the improvement measures of the slide machine is mainly the wear of the waiting surface of the firing arrester iron and the waiting card groove of the bolt frame. **The Z89 heavy machine gun uses a trigger to control the movement of the firing arrester, and uses the firing arrester to buckle the moving parts in the rear into a ready state. When shooting, the parts that the firing arrester and its interlock are to produce impact and friction, especially when the firing arresting iron is fastened with the moving parts, the impact load is very large, therefore, the waiting surface of the firing arrester and the waiting slot of the bolt frame is easy to wear.
Improvement measures: method 1 is to select materials with higher wear resistance and strength on the design of the firing arresting iron and the waiting surface of the bolt frame on the basis of not changing the original firing mechanism, and carry out special treatment to improve its strength and wear resistance, so as to ensure that the firing mechanism and the bolt frame can withstand a large impact during the shooting process and ensure that the action is reliable during the shooting process. The second method is to improve the structure of the firing machine. In order to fundamentally eliminate the occurrence of slip machine failure, it is necessary to redesign the firing mechanism of the **Z89 heavy machine gun to improve its reliability.
In the process of non-shelling failure and improvement measures, there are often moving parts that do not recoil in place, resulting in the occurrence of non-shelling failure. After inspection, the gas regulator was installed correctly and there was no ablation, the grappling hook and throwing shell were not damaged, the chamber was not dechromized and corroded, and there was no oil and dust in the receiver. The reasons are: First, in the process of recoiling, the locking bamboo shoots on the nose collide with the guide edge on the receiver, resulting in the wear and bruise of the guide edge, which hinders the backward movement of the moving parts. The second is that the guide edge on the bolt frame and the guide groove on the receiver are not properly matched, and the surface of the guide groove on the receiver is seriously worn, and burrs appear, which increases the resistance of the movable parts when recoiling, resulting in the recoil is not in place.
Improvement measures: For bruises and burrs, they can be sent to the repair shop for repair. But if you want to solve the problem at the root, you have to make improvements. First, in the design and production process, the assembly error is strictly controlled to ensure that the moving parts can move smoothly and flexibly under the severe vibration of live ammunition shooting. The second is to strengthen the surface that is prone to collision and wear, such as the ceramic composite coating process, to increase the wear resistance of the parts.
In the process of use, the parts that are prone to breakage include the loading handle, the handle of the safety machine, the firing base and other parts.
The part of the filling handle fracture is the connection between the loading handle and the pull handle, and the reason for the fracture is that the stress concentration area is there, and when the backward loading starts, the backward force on the pull handle is transmitted to the loading handle with the slider as the fulcrum. The force is larger, and the force at the junction between the loading handle and the pull handle is not straight backward, but backward to the left. When the loading handle is in place, the force acting on the handle does not stop immediately, and when the loading handle stops moving, the force acting on the connection between the loading handle and the handle to the left is increased, and then the loading handle breaks.
The reason is that in the process of gun recoil, inertia makes the fuse axial turn backwards, driving the fuse handle to rotate forward, and when the front end of the fuse handle touches the protrusion on the firing frame, it is forced to stop moving. The force on the front end of the safety lever is high, which is able to knock the protrusion on the firing frame into a visible dentation. The gun recoils repeatedly when firing, and when the material of the safety handle reaches the fatigue limit, the safety handle breaks.
The firing frame is broken, and the guide edge of the firing base and the guide groove on the casing cooperate with each other, so that the firing machine is reliably fixed on the casing, which belongs to a rigid fit. As long as each shot is formed in a state of readiness, the firing base will be impacted, and after the firing base is repeatedly hit by a strong impact, the temperature of the firing base will continue to rise with the impact, and when the stress on some parts of the interior exceeds the fatigue limit of the material of the base, it will produce the fracture of the firing base.
Improvement measures: The above three parts that are prone to fracture are aluminum alloy materials, and the common reason is that the force is large and the strength of the material is not enough. Therefore, it is necessary to reduce the occurrence of fracture failure by replacing materials with good toughness and rigidity, or improving the strength of aluminum alloys, so as to improve the reliability and failure rate.
Improve the firing mechanism and increase the single-shot shooting mode**The Z89 heavy machine gun only has a burst fire mode, which causes a lot of inconvenience in actual use. In the process of training and assessment, single shot is often required, such as in the correction of fire effect and the assessment of live ammunition. At present, there are two ways to achieve single-shot shooting: one is to load one bullet in the air above the bullet chain, so that when the next bullet is fired, it needs to be reloaded, which will cause damage to the bullet chain and waste valuable training time; The second is to pull the bolt backward to position, and put the bullet directly into the chamber, which has certain potential safety hazards and does not conform to the operating procedures. Therefore, it is proposed to improve the firing mechanism and increase the single-shot firing mode to achieve both single and continuous firing.
In the process of improving the connection between the gun and the mirror and increasing the speed of the combination, the team support is required to shoot quickly when carrying out fire support, but sometimes it cannot be fast, because the combination of the scope and the receiver is bolt-fixed, and the installation is time-consuming due to the large number of fastening screw turns. After the scope is installed on the gun, it is easy to loosen due to large vibration during shooting, and it needs to be retightened after loosening, which affects the rate of fire. It is proposed to improve the way the sight is mounted and tightened, preferably with a dovetail groove.
Develop a fire control system to improve combat effectiveness**The Z89 heavy machine gun still stays in the way of visual inspection and rough ranging by using a scope, and cannot be completely converted into a precision strike, resulting in the bullet not being able to exert its due combat effectiveness. It is recommended to develop a simple fire control system, so that the heavy machine gun can find the target at the fastest speed, complete the aiming and shooting in the shortest time, and damage the target with the least ammunition, so as to become a squad support for all-weather combat and precision strikes.