The initial velocity of a Kalashnikov bullet directly depends on the length of the barrel of a particular weapon and the thermodynamic properties of the gunpowder used. For standard AK-74 This parameter is about 900 meters per second, while the shortened AKS-74U gives much lower values, which critically affects the accuracy and penetration ability of the ammunition. Understanding these physical processes is essential to assess the actual combat characteristics of small arms.
The differences in ballistic data are due to the time during which powder gases affect the bottom of the bullet inside the barrel channel. The longer this contact is, the more energy is transferred to the metabolized body, but there is a limit after which the friction on the cut begins to extinguish the inertia. That's why. starting-speed It is a derivative of many engineering compromises laid by designers in the design of the system.
Physical bases of the formation of speed in the channel of the barrelThe process of shooting in automatic systems, such as AKM or AK-12It begins with the ignition of the capsule and the instantaneous combustion of the powder charge. The resulting gases create enormous pressure that pushes the bullet forward, accelerating it to supersonic values in fractions of a second. The key factor here is the tightness of the obturation, provided by the leading belt of the bullet, which crashes into the cuts.
It is important to bear in mind that powder-pressure It reaches peak values not at the time of ignition, but when the bullet has already passed part of the path along the barrel channel. For intermediate cartridges of caliber 5.45 mm or 7.62 mm, this peak falls on the first 10-15 centimeters of movement. After passing the peak pressure, the speed continues to increase by inertia until the bullet leaves the muzzle slice.
⚠️ Warning: Exceeding normal barrel pressure due to the use of substandard cartridges or foreign objects can cause the barrel to bloat or destroy the weapon.
The ambient temperature also makes its own adjustments to ballistic characteristics. Cold powder burns more slowly, which reduces pressure and, as a result, reduces the initial speed of the bullet. On the contrary, heated ammunition is able to show higher results, but with the risk of exceeding the permissible loads on the mechanism.
The effect of the barrel length on the ballistics of various modificationsThe length of the barrel is the determining geometric parameter that affects the final speed of the bullet on the cut. In the line of Kalashnikov assault rifles, this parameter varies from 415 mm in the classical one. AK-74 up to 206.5 mm in compact AKS-74U. The difference in length almost twice leads to a significant drop in energy performance in short-barreled versions.
- 🔹 Classical machine AK-74 With a barrel of 415 mm, it ensures complete combustion of gunpowder and maximum efficiency.
- 🔹 Shortened version AKS-74U Loses a significant part of the speed due to premature release of the bullet from the range of gases.
- 🔹 Modern type specimens AK-12 have optimized pitch of cuts to compensate for losses at different barrel lengths.
- 🔹 Experimental samples with an elongated barrel show an increase in speed, but become less convenient to operate.
The reduced speed when using short barrels leads to a steeper trajectory of the bullet and a reduced range of direct shot. This means that the arrow has to adjust for distance more often, especially at the limiting distances. Besides, muzzle-fire In short-barreled samples, it is much brighter due to the burning of gunpowder outside the barrel.
Comparative analysis of cartridges 5.45 mm and 7.62 mmThe transition of the Soviet army to a caliber of 5.45 mm was due to the need to increase the initial speed of the bullet while maintaining the weight of the wearable ammunition. A light bullet of smaller diameter is accelerated to higher speeds than a heavy bullet of 7.62 mm caliber using similar mass powder charges. This allowed to improve the trajectory deck and reduce the impact of the side wind.
| Parameter | 7.62x39 mm (AKM) cartridge | Cartridge 5.45×39 mm (AK-74) | Cartridge 5.45x39 mm (ACS-74U) |
|---|---|---|---|
| Initial speed (m/s) | 715 | 900 | 735 |
| Bullet mass (g) | 7,9 | 3,4 | 3,4 |
| Muzzle energy (J) | 2026 | 1370 | 920 |
| Direct firing range (m) | 350 | 440 | 310 |
Despite the smaller bullet mass, the 5.45 mm cartridge has a high penetration capacity at medium distances due to the high speed and design of the bullet. A 7.62 mm heavy bullet retains energy better at ultra-long ranges and when passing through obstacles, but has a more pronounced parabolic trajectory. The choice of caliber is often dictated by tactical objectives and the conditions of use of weapons.
Calibre change history
In the middle of the XX century, military theorists came to the conclusion that the probability of hitting a target with one shot at real combat distances (up to 400 m) is small. Therefore, the priority has shifted towards increasing the density of fire and the likelihood of hitting when firing bursts. A light high-speed bullet prowls less in the barrel channel and has a gentler trajectory, which simplifies the shooting.
The role of powder charge and ammunition qualityThe quality of the gunpowder and the accuracy of its attachment are critical factors determining the stability of the initial velocity from shot to shot. The velocity spread, called interval-rateIt directly affects the vertical rupture of bullets on the target. For army cartridges, certain deviations are permissible, but for sniper shooting even minimal fluctuations are unacceptable.
Modern nitrocellulosic powder burns at a certain rate, depending on the shape of the grains and the presence of graphite. Violation of production technology can lead to unstable combustion, which will cause either an unacceptable drop in speed or a sharp jump in pressure. In low temperatures, some types of gunpowder can give ignition passes or lingering shots.
☑️ Factors affecting the speed of the bullet
Muzzle devices and their effect on the speed of the bulletInstallation of muzzle devices, such as DTK (mullibrating compensator) or NG (flame suppressor), also makes changes in the picture of the bullet exit. Although their main purpose is to reduce recoil and mask the shot, design features can have a slight effect on speed. Some types of DTC create additional backpressure, theoretically increasing the exposure time of gases, but in practice this effect is minimal.
⚠️ Warning: The use of abnormal or damaged muzzle devices can lead to unstable bullet flight immediately after leaving the barrel, which dramatically reduces accuracy.
⚠️ Warning: The use of abnormal or damaged muzzle devices can lead to unstable bullet flight immediately after leaving the barrel, which dramatically reduces accuracy.
Flame suppressors, by contrast, often have an internal structure that can slightly turbulate the flow of gases, but should not come into contact with the bullet. It is important to monitor the condition of the fly attachment and the sighting bar, since vibrations from the muzzle device over time can knock down the shooter. For tasks where maximum starting-speedSometimes use smooth barrels without cutting in the muzzle part, but this is rare for automatic machines.
The practical importance of speed for shootingFor practical shooting, the initial speed determines the time of the bullet’s flight to the target and the magnitude of the trajectory reduction. Knowing the precise ballistic characteristics of their weapons, the shooter can effectively hit targets at long distances by making the necessary adjustments. At distances up to 100 meters, the impact of speed is minimal, but already at 300 meters, the difference in 50 m / s can be several centimeters of decrease.
- 🎯 High speed reduces the response time of the target to the shot, increasing the likelihood of hitting moving objects.
- 🎯 The impact of the side wind on the demolition of the bullet is reduced, which simplifies shooting in difficult weather conditions.
- 🎯 The penetrating capacity of light armored barriers and personal protective equipment is increasing.
To maintain a stable initial speed, store the cartridges in a dry place at room temperature and avoid prolonged heating in the sun or in the car in summer.
To maintain a stable initial speed, store the cartridges in a dry place at room temperature and avoid prolonged heating in the sun or in the car in summer.
FAQ: Frequently Asked Questions on Ballistics
How does air temperature affect the speed of the bullet?
With increasing temperature, the rate of burning of gunpowder increases, which leads to an increase in pressure and the initial speed of the bullet. At -50°C, the speed can drop by 10-15% compared to normal conditions (+20°C).
Why is the AKS-74U so slow compared to the AK-74?
This is due to the short barrel length (206.5 mm vs. 415 mm). The gunpowder does not have time to completely burn and transfer energy to the bullet until it departs from the channel of the barrel, which leads to a loss of speed and a strong muzzle flame.
Can you increase the speed of the bullet at home?
Absolutely not. Any manipulation with the cartridge (change of gunpowder hanging, replacement of the bullet) is life-threatening and can lead to the explosion of weapons. Factory characteristics are optimal for safety.
Does the scalp impact the initial speed?
Yes, with strong wear of cuts (nagar, erosion), the tightness of the obturation is violated. Powder gases break past the bullet, which reduces the efficiency of acceleration and reduces the initial speed.
The initial speed of a bullet is not a constant value, but a variable parameter that depends on the length of the barrel, temperature, quality of the ammunition and the condition of the weapon.