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Bullets for Beginners
Guns are generally classified according to use, size, and tradition. This varies among the military services. The basic distinction is between small arms and artillery. Any gun below a 20-millimeter bore size is generally classified as a small arm. An alternative term gaining increasing currency is "light arms," to include individual and light support weapons.
Conventional bullets for a rifled barrel usually have a lead core with a surrounding copper jacket of a diameter which is nominally the same as the groove diameter and is thus slightly oversize or an interference fit with regard to the bore diameter of the barrel of the weapon with which it is intended to be used, the copper jacket of the bullet being engraved and slightly compressed during its passage down the barrel of the weapon by the helical rifling grooves in the barrel. The bullet is spun by the rifling grooves to stabilize its flight, but a considerable proportion of the energy produced by the propellant in the casing containing the bullet is lost through friction between the bullet and the rifle barrel caused by the engraving of the bullet, the friction generating heat in the barrel.
Bullets can be optimized for minimum time of flight, minimum dispersion, maximum retained kinetic energy, minimum cross wind sensitivity, minimum ballistic drop, maximum penetration, and limiting maximum range. For instance, a heavier bullet launched at lower muzzle velocity is a bullet designed to minimize cross wind sensitivity. As the bullet gets heavier, more of the projectile body can be dedicated to ogive length, reducing drag. Heavier, faster, lower drag is generally better, but with a fixed case volume, it is not possible to improve all of these attributes simultaneously. A bullet optimized for one parameter is often the worst solution for another important parameter. Optimizing one parameter requires compromise on others.
Small arms and machine-gun projectiles are made of solid metal; however, projectiles of 20-mm guns and larger have many components. The form of the forward end of the projectile is an ogival curve (generated by revolving an arc of a circle about a chord) that is aerodynamically efficient. Behind the ogive, the projectile is cylindrical with the exception of the bourrelet, which is slightly larger than the diameter of the body to reduce the surface area (and thus the friction) of the projectile contacting the gun bore. Near the after end of the projectile is the rotating band, which is actually larger than gun bore diameter to engage the rifling grooves and seal the bore while supporting the aft end of the projectile. The rifling actually engraves the rotating band to ensure a gas-tight seal. Aft of the rotating band the cylindrical shape may continue to the base of the projectile or it may be tapered to a "boat tail."
A complete round of small-arms ammunition is known as a cartridge, and is made up of the following components:
- Bullet: The bullet in general is cylindrical. The nose may be round, as in the cal, .50 bullet, or ogival as in all service rifles and machine gun bullets. The base may be square or boattailed.
- Armor-piercing bullets contain a core of hardened steel.
- Ball usually contain a slug of antimony hardened lead except in case of the cal, .50, wherein the outer core is of soft steel.
- Tracer contains a lead slug, and a chemical composition in the rear.
- Incendiary bullets contain an incendiary composition.
Types include the following:
Cartridge case: The cartridge case is the means whereby the other components are assembled into the unit. It also provides a waterproof container for the propelling charge.
Primer: Percussion
Propelling charge: The propelling charge consists of a quanity of smokeless powder. The weight of the charge is not constant. It is adjusted for each powder lot to give the required velocity with pressure within the limits prescribed for the weapon in which it is fired.
NATO Standard Ammunition
Physiologically, a determined adversary can be stopped reliably and immediately only by a shot that disrupts the brain or upper spinal cord. Failing to hit the center nervous system, massive bleeding from holes in the heart, or major blood vessels of the torso causing circulatory collapse is the only way to force incapacitation upon an adversary, and this takes time. For example, there is sufficient oxygen within the brain to support full, voluntary action for 10 to 15 seconds after the heart has been destroyed.
The pointed ogival "spitzer" tip, shared by all modern military bullets, reflects the balancing by nations of the criteria of military necessity and unnecessary suffering: its strepdined shape decreases air drag. alloying the bullet to retain velocity better for improved long-range performance;a modern military 7.62mm bullet [with all lead core] will lose only nbout one-third of its muzzle velocity over 5O0 yards, while the same weight bullet with n round-nose shape will lose more than one-half of its velocity over the Same distance. Yet the pointed ogivnl "sptizer" tip shape also leads to greater bullet break up, and potentially grenter injury to the soldier struck by such a bullet vls-a-vis a round-nose [full metal jacketed] bullet.
Weighing the increased performance of the pointed ogival "spitzer" tip bullet against the increased injury its breakup may bring, the nations of the world through almost a century of practice - have concluded that the need for the former outweighs concern for the latter, and does not result in unnecessary suffering as prohibited by the 1899 Hague Declaration Concerning Expanding Bullets or article 23e of the 1907 Hague Convention IV. The 1899 Hague Declaration Concerning Expanding Bullets remains valid for ｅxpression! of the principle that a nation may not develop or employ a bullet that expands easily on impact for the purpose of unnecessarily aggravating the wound inflicted upon an enemy soldier. Such a bullet also would be prohibited by article 23e of the 1907 Hague IV.
Discussions of this issue were undertaken at the second session of the ICRC Conference of Government Experts on the Use of Certain Conventional Weapons in Lugano in 1976. No consensus was reached, and the three Protocols attached to the 1980 Convention do not contain any ban relating to the use of small-calibre projectiles. Instead, the UN Conference adopted a resolution in 1979 inviting governments to carry out further research on the wounding effects of small-calibre weapon systems and appealing to all governments "to exercise the utmost care in the development of small-calibre weapon systems, so as to avoid an unnecessary escalation of the injurious effects of such systems".
A bullet which is fully enclosed in a metal jacket, as are virtually all military rifle bullets today, will start to turn around a lateral axis at some distance after entering the body. once it starts to turn, the rate of turning increases rapidly; the angle of incidence reaches 90 degrees and the bullet continues turning until it is travelling nearly tail first. After that, it can partly turn several more times before entering the last phase, when it will again be travelling tail first. Depending on its construction, a full-metal-jacketed bullet can deform or break up because of the stresses placed on it during turning, but deformation or break-up of a full-metal-jacketed bullet is a by-product of turning and not an independent process, although, once it happens, the deformation or break-up adds to the wounding effect because of the increase in the surface area of bullet material pressing against the tissues.[20]
The turning, or "tumbling", of a bullet is thus the critical mechanism resulting in severe injury, and the likelihood of causing a severe wound will depend on how far a bullet penetrates the body before turning. An ammunition designer who is intent on inflicting the greatest possible damage will want to have the bullet turn as soon as possible, thus achieving the same effect (rapid transfer of most or all of the bullet's kinetic energy) as with the outlawed dumdum bullet. A designer wishing to avoid severe wounds will want the bullet to travel as far as possible before turning: a soldier hit in the arm or leg will be out of action temporarily but is unlikely to suffer permanent injury or to die.
Small Caliber ammunition types are differentiated by projectile tip identification paint, i.e., tracers are painted red or orange, armor piercing are black, dim trace are purple, etc.
Armor-piercing, or target-penetrating, projectiles having an outer jacket and containing tandemly-arranged incendiary and explosive charges are conventional ordnance used in both offensive and defensive modes. Such projectiles are particularly effective when their destructive force is unleashed after they have penetrated the surface layers of the target. This is especially true for targets having electronic controls or computers susceptible to damage from metal fragments. Thus, it is common practice to incorporate some means for delaying ignition of the incendiary and/or explosive charges carried by the projectile until after impact.
With incendiary initiated explosive projectiles which are commonly called "HEI" (High Explosive Incendiary) or "PIE" (Pyrotechnically Initiated Explosive) rounds, the destructive force unleashed after impact and penetration of the target is ordinarily generated by detonation of the explosive charge which is contained in a metal body of the projectile rearward of a forwardly-located incendiary charge. The explosive charge is typically set off by a shock wave generated by ignition of the incendiary charge. Ignition of the incendiary charge in the projectile tip is caused by impact of the rapidly spinning projectile tip with the target. However, in the case of many projectiles, the duration of detonation of the explosive charge is relatively short and the magnitude and extent of its destructive impact suboptimal within the target.
Flechette type APFSDS projectiles utilizing high strength or high density rod penetrators have been developed for small caliber 5.56 and 7.62 millimeter rifle systems, but without allowance for a tracer cavity in the flight projectile. Fin stabilized APFSDS projectile designs incorporating an adequate tracer cavity and developed for larger caliber systems do not efficiently scale down to small caliber projectiles due to the complexity of their sabot geometries which were optimized for the unique parameters of the larger caliber systems. Early fin stabilized APFSDS projectile designs for smaller caliber 5.56 and 7.62 millimeter guns did not provide for a tracer cavity in the rear of the flight projectile.
A more effective and efficient fin-stabilized, discarding sabot projectile incorporating an adequate tracer cavity with a deep armor penetrating projectile for small arms applications design overcomes many of the shortcomings inherent in earlier small arms APDS and APFSDS projectiles, such as: faulty structural design, poor sabot discard, reduced projectile accuracy at long range, low muzzle velocity due to high sabot parasitic weight, and inadequate armor penetration. Although a good start in the right direction for small caliber APFSDS projectiles, this design requires the use of several high precision manufactured obturator components, to ensure adequate performance and safety reliability. Reducing the complexity of the current state-of-the-art in obturator design will result in greater projectile performance, achieved with less expensive components, assemblies, and manufacturing processes.
Accordingly, it is advantageous to provide an armor piercing fin stabilized discarding sabot (APFSDS) projectile for small caliber guns which minimizes sabot parasitic weight and structural complexity, facilitates rapid sabot separation upon muzzle exit without introducing trajectory inaccuracies for the rod projectile, maximizes armor penetrator weight and length, and provides for an adequate tracer cavity in the rear of the flight projectile.