Ballistics

This is an ordered field of study that deals with flights, their behaviors and the resultant effects of the projectiles. Projectiles in this field include; rockets, bullets and bombs. Ballistics may also refer to an art of designing as well as accelerating projectiles so as to achieve the desired outcome. A ballistic body is an entity that can move and its appearance texture and shape can be modified. It can also be forces or substances for instance, pressure in gases which are typically used in guns. Ballistics is a pertinent subject which helps crime investigators to determine the type of the gun used during the crime. This is because the path and the damage caused by the bullet can be assessed. (Hamilton, 1908)

All weapons involve shooting the ammunitions which traditionally have cartridge cases, explosive chemical, powder and a bullet; there is also the mixing of chemicals in a pellet known as primer. In these weapons, the gunpowder and the ball are fitted inside the case and the primer is at the base of the cartridge casing of the gun. Thus, when a gun is pulled, a spark is the one that explodes the chemical powder, and the blast drives the bullet to fly forward. This happens at the end of the barrel known as the muzzle.

Guns and other projectiles use kinetic energy and bullets are to resist external forces acting on them during acceleration to avoid easy deceleration. These two factors are always taken into consideration during the construction of bullets and other ammunitions. Bullets are classified according to their structure and thus there are solid ones, which are sometimes referred to as homogeneous bullets since they consist of only one material or element. There are jacketed bullets which have cores’ coated with a thin layer of a material of another substance and there are tracer bullets, which can be either, fully jacketed or solid bullets.

In weapons, propellants are the main source of acceleration energy which enables a projectile to attain a maximum velocity. This energy is normally produced in a variety of ways, and its combustion generates a gas pressure to propel the projectile. A cartridge case serves the following function; it directs the projectile in the first section of the flight, it acts as a container for transportation of the primer and the propellants, it positions the projectile and the whole weapon, and it provides an accommodation to the extractors resistance of the missile which is responsible for a uniform combustion of the chemical powder. (Moss, 1995) The field of ballistics is subdivided into three namely; interior ballistics, exterior ballistics and terminal ballistics.

Interior ballistics

This is concerned with what normally happens between the cartridge that is fired and the projectile that leaves the muzzle.  When the primer lights the propellant, a gas is produced which quickly builds up a greater amount of pressure. This pressure in turn pushes the projectile out of the casing and upward the barrel. The distinguishing feature of the propellant powder is that the pressure generated by the gas when at its peak is normally at the same time when the projectile commences its journey up the barrel. This explains why the gun is thicker at this part than other parts for it to withstand pressure. (Ackey, 1971)

When the projectile moves up the barrel, it tends to create a space for the gas to expand and on the other hand, the same gas decreases. This same gas is vital as the projectile move away from the muzzle, and this result to a rapid expansion in the air causing a gun fire. This last expansion plus the end of the friction that existed between the projectile and the barrel boosts the projectile so that its maximum velocity is achieved beyond the gun’s muzzle.

In essences, weapons function at different gas pressures for instance shot guns and pistols act at lower pressures while automatic cannons and rifle act at higher pressures. For higher velocities to be achieved, magnum and military pistols ammunitions that are used in sub machine guns are loaded with high pressures than the normal ones. This, therefore, shows that it is dangerous to use these ammunitions in normal guns. Cannon and rifle ammunitions are put to a practical pressure since the barrel risk of tear and wear is taken into consideration as well as chances of the case sticking to the chamber and other technical problems that are likely to occur.

The chamber pressure is normally measured in the metric system which uses, Kg/cm2, bar which is an atmospheric pressure measurement also the scientific megapascal (MPa). These measurements can be converted as; 1MPa=10bar=10.2kg/cm². The chamber pressure for shot guns is 75-90MPa, for the pistols rounds are 100-240 MPa and for rifle rounds is 310-380 MPa. The extreme loading can be up to 450MPa.

In this subfield, bolt thrush is a cartridge element that influence the gun design since it refers to the rearwards push on the gun bolt that is caused by the gun firing. This usually relies on two things; the chamber pressure and the inner diameter of the base of the case. This means that the wider the case to be, the larger the surface area of the pressure to act. Thus, if a cartridge case is long and thin, it can develop the same chamber pressure like a short flat one with twice the internal base area. This short flat one develops twice a bolt thrust than the long thin one, meaning that the greater the bolt thrush the stronger the gun’s locking mechanisms.

In interior ballistics, a suppressor is an indispensable tool since it allows for the expansion of the gas within a controlled manner. This suppressor is attached to the muzzle of the weapon so that during expansion the gas is cooled, the pressure drops, and the ammunition are released slowly by slowly to avoid violent bursting. This explains why suppressors are bulky and if the propellants are more, big suppressors are needed. On the other hand, if a weapon is unsuppressed, the muzzle report becomes a source of noise. Supersonic projectiles with muzzle velocities of over 340m/s generate supersonic cracks which can be heard from far. An example of supersonic projectiles is the rifle ammunition while pistol ammunitions are subsonic. The suppressors have been found to be the best on subsonic ammunitions. When suppressors are used with rifles, the foe can hear the cracking sound but can not establish the direction of origin unless sophisticated equipment is used to detect the direction. (Heard, 2008)

In interior ballistics, muzzle energy is developed by the cartridge and is measured in joules. Joules is arrived at by multiplying the weight of the projectile by the square of the muzzle velocity in m/s hence dividing it by 2000 which is a constant. This muzzle energy is generated by a certain amount of a propellant powder, and this relies on the caliber of the weapon. This means that the bigger the caliber, the higher the energy to be produced by a given amount of the powder. The law of diminishing returns applies to the production of muzzle energy since there is a practical limit of the powder in any caliber. This is highlighted by the fact that using a larger cartridge case which has a lot of propellant attains a slighter increase in velocity from the extra powder used. If a cartridge does not use its propellant efficiently, it is normally termed as an over-bore.

In conjunction with this, different projectile weights produce different energy levels.

Another important element in interior ballistics is the recoil effect which is determined by the gun characteristics and the cartridges’ ballistics. The recoil impulse of a weapon is usually created when a cartridge is fired. Recoil has two fundamental components namely; the momentum of the projectile and the rocketing effect of the disappearing gas. The recoil of any weapon is calculated by (bullet weight multiplied by muzzle velocity) + (propellant weight multiplied by 1200 m/s). This means that a cartridge firing at 5g bullet at 500m/s it has the same bullet momentum with that firing at 10g bullet at 250 m/s. The recoil caused by the disappearing gas is not easy to calculate since it relies on the relationship that exists between the length of the barrel and the burning features of the powder.  This shows that a barrel with a normal length produces high-muzzle velocity which in turn leads to higher recoil through the bullet momentum and vice-versa.

Exterior ballistics

This is determined by the muzzle velocity and the coefficient of ballistics. The co-efficiency of ballistics is vita; since it establishes the rate at which the projectile slows down. As it goes with the muzzle velocity, it determines the maximum range and the actual moment to fly to any distance. This time of flight then depicts the rate at which it falls as it normally occurs at a constant rate because of the velocity. This co-efficiency of ballistics, the curved path produced, and the gravitational dropping of the projectile is known as trajectory. (Carculli, 2007)

In long range shootings, a minimal time flight is recommended since it maximizes the chances of hitting by decreasing the time of flight and the flattening of the projectiles trajectory. This in turn, enables the projectile to strike the intended target at a higher velocity with an immediate effect. For this to be achieved more propellant is needed and the barrel of the weapon should be longer than the desired.

Ballistics co-efficiency is determined by sectional density (SD) and the form factor (FF). Sectional density is the ratio that exists between the projectiles weight and the caliber of the weapon. It is usually calculated by multiplying the projectiles’ weight by 1.422 then dividing it by the caliber square which is in millimeters. FF is the element which measures the aerodynamic efficiency of the projectiles shape. Thus, it is not easy to calculate unless there are manufacturers’ data provided. FF varies among the supersonic and the subsonic velocities since the shape that acts best at subsonic speeds are not adept at supersonic velocities. Streamlining can be done at subsonic velocities since drags are caused by low- pressure zones created at the base of the projectile while with supersonic speeds, a nose shaped structure is needed but the rear end do not matter a lot. Addition of tracers helps generate a gas which in turn aids to fill the low-pressure zone at the base of the projectile thus dragging can be reduced. This in the long run gives them a different trajectory. (Rollins, 2004)

Terminal ballistics

 In terminal ballistics, there are two significant aspects namely; the effect against the armour and the effect of the projectile strike against a soft surface or the target. When a projectile is directed towards a soft surface, it is destabilized as compared to a hard target. The underlying reason is its shape which is towards the centre of gravity of the ammunition is always towards the rear end, and as such prefers naturally to fly when the base is at the fore front.

 When the bullet is being released and starts travelling base first, it is normally referred to as tumbling. It is a scenario caused when a bullet spins by means of the rifling maintaining the flying bullet tumble at the same time since small bullets tumbles faster than the large ones given that other things are kept constant and equal. Small identical bullets with different internal constructions tumble at different speeds. For instance, a bullet manufacture in Yugoslavia which has a lead core tumbles much faster than a bullet from Russia which is steel cored and uses the same cartridge. Thus, various tricks have been used to improve the chances of a bullet tumbling. For example, the current Russian bullet is 5.45mm, and has a hollow tip while a British one has a light weight tip filler and the weight is concentrated at the rear end of the bullet. On the other hand, if the bullet has a weaker coating, the stresses caused by the tumbling may break this process is termed as fragmentation and usually enhance the wounding effect caused. Bullets do so when in higher velocities, and this limits them to achieve a longer range especially when fired from carbines of lower muzzle velocities. Thus, fragmentation is not a requirement of any military bullet since 7.62*51 NATO bullet does not fragment while a Germany one do so by accident and not by design (NRA Firearms Fact Book, 3rd edition, 1989).

Hunters often have claimed that the striking velocity of the bullet goes higher beyond 700m/s, and the result is that the hydrostatic shock starts to appear and this effect does not replicate itself among the people. There are instances where soldiers have fought continually despite receiving serious wounds from high- speed bullets. Critical shocks impacts only occur if the bullets go beyond the speed of sound in the flesh which is just around 1500m/s. (Karl, 1994)

In conjunction to this, there is stopping power which refers to the opponent so that no further fighting continues. Low powered weapons are deadly and more power is needed for it to attain an effective stopping capacity. Hence bullets placement may be significant in achieving this. This is because of it is much effective to hit an immediate area with a low powered bullet than to cause a small injury with high powered weapons.

Conclusion

In conclusion, ballistics is crucial since it aids in the construction of effective weapons since several measures can be followed. For instance, the size of the caliber, the amount of the propellant powder to be used, the weight of the cartridge and other factors that determine the acceleration of the projectiles.