Sure, there’s math. But ballistics is also intuitive. It’s how we describe things hurtling through air.
A basketball at rest in a corner of the gym is a lot like a bullet in the chamber of a rifle. Neither is very interesting, because neither is moving. Put the basketball in play or fire the rifle, and you set in motion a raft of variables that comprise the study of ballistics. Acceleration, deceleration, velocity, mass, energy, inertia, drag, profile, sectional density and the tug of gravity—to name just a few—affect the paths of all objects hurled through our atmosphere, from rocks to rockets. The name “ballistic missile” is oddly redundant, because every missile becomes “ballistic” at launch. Every projectile has ballistic properties.
In this book, ballistics has to do with bullet behavior. Once it leaves the muzzle, a bullet has only momentum to carry it (unlike a guided missile, which gets both power and direction during flight). A firm grasp of ballistics is a first step toward more effective shooting. Ballistics is really a three part discipline. Interior ballistics describes the turbulence inside a rifle: primer ignition, gas production and pressure, bullet release and acceleration. Exterior ballistics has to do with bullet flight—velocity, energy and trajectory as the bullet moves from muzzle to target. Terminal ballistics comes in after the strike; most commonly it’s a measure of bullet penetration and upset in a game animal or an adversary.
Interior ballistics is mostly a laboratory science. Sophisticated instruments measure high pressures over tiny slices of time. Charting pressure curves, ballisticians assess performance and design propellants and bullets for commercial loads. Though it represents a small fraction of the eye–blink delay between striker fall and the bullet’s impact 100 yards away, the launch has a profound effect on bullet trajectory and accuracy. Few shooters, though, are equipped to measure interior ballistics or manipulate them based on what happens before bullet exit. Riflemen have a much easier task with exterior ballistics. You can clock a bullet with a chronograph to determine its velocity. Plugging bullet speed and weight into a formula yields a measure of its energy. Drop and drift are a snap to determine—simply measure displacement at the target. By changing loads, you affect both interior and exterior ballistics, except for pressure signs on cartridge cases, meaningful measures of bullet performance all come forward of the muzzle.
Bullet velocity, energy, and trajectory have become standard items in ballistics charts provided by makers of ammunition and ammunition components. The properties of bullets in flight are relatively easy to quantify, very easy to compare in charts. With them, you can assess the practical reach of your rifle (as regards killing power, not accuracy) and its most efficient zero range.
Understanding ballistics, you can wring the most reach, accuracy, and power from your rifle.