Internal ballistics is associated with performance of a projectile within the internal functions of a firearm. Internal ballistics deals with multiple factors such as types of barrels, rifling, bores and chokes in both rifles and shotguns.
In all rifles and pistols, the rifling of the barrel is designed to stabilize lead bullets in their flight toward the target. The use of non-lead bullets in such barrels can cause problems with gyroscopic stability and hence accuracy, due to differences in bullet density and length.
As lead shot is relatively soft and malleable, it can travel through the barrel of a shotgun at a high rate of speed without damaging the bore. Although the use of plastic shot cups can alleviate bore damage with steel shot in most cases, the harder alternative metals are less attractive than lead ammunition to many hunters who own older shotguns because steel shot may cause ring bulge (a slight expansion of the choke) in older, tightly choked shotguns.
External (aka, exterior) ballistics is the study of the flight and behavior of the projectile from the time it exits the firearm until it strikes the target. It is literally rocket science.
External ballistics consists of a number of complex factors. Bullet shape and density of lead versus alternative metals affect the performance of a projectile after it leaves the barrel. Exterior ballistics is relevant to the discussion of ammunition because lead ammunition performs differently in flight than non-lead alternatives. Because lead ammunition is generally denser, it maintains velocity and energy during flight. Accordingly, lead ammunition is superior to non-lead alternatives because the alternatives retain less down-range energy.
While some alternative ammunition are able to offer similar performance to lead at close range, the lack of density of non-lead alternatives begins to undermine their ballistic performance above 30 to 40 yards for shotguns and makes lead a superior ammunition for long range targets.
The following resources provide detailed information on external ballistics and calculating projectile trajectories:
- Heard, Brian J., Handbook of Firearms and Ballistics: Examining and Interpreting Forensic Evidence. Singapore: Wiley-Blackwell, 2008.
- Rinker, Robert A., Understanding Firearm Ballistics. Basic to Advanced Ballistics Simplified, Illustrated & Explained. USA: Mulberry House Publishing, 2003.
Terminal ballistics (aka, terminal performance) is the study of how a projectile affects and transmits energy to the intended target upon impact. Terminal performance is a key element in the discussion of proposed lead ammunition bans, because various types of ammunition strike and affect their targets differently.
Projectile velocity, energy, weight, range, type, caliber and personal preference of the shooter are all factors of a projectile’s terminal ballistics.
Terminal ballistics can be divided into two categories, penetration potential (the capacity of a projectile to penetrate various materials), and wound ballistics (the effect that the projectile has on living organs).
Terminal performance of ammunition is largely influenced by projectile deformation upon impact. Because lead ammunition is very malleable, it deforms readily upon impact over a wide range of velocities, presenting a reliably large frontal area which rapidly destroys tissue, killing the game cleanly and humanely. Alternative metal ammunition is harder and does not deform as reliably over as wide a range of velocity as lead ammunition. As a result, non-lead ammunition can over penetrate game leaving a narrow, less effective wound channel, causing wounding and crippling of game, which can allow game to escape and slowly die in the field. Accordingly, lead ammunition provides superior terminal performance with significant penetration and mortal wounding capability.