What a Projectile Keeps Downrange
Retained velocity is the speed a projectile still carries at a given distance after drag has slowed it from its muzzle value. Retained energy is the kinetic energy that remains at that same point, calculated from the projectile's mass and its current velocity. Together they describe how well a design holds its performance as range increases.
The Shape of the Velocity Curve
Velocity does not fall at a steady rate. Drag force rises with the square of speed, so a fast projectile sheds velocity quickly at first, then more gently as it slows. The result is a curve that drops steeply near the muzzle and flattens with distance, meaning the first hundred yards often cost more speed than a hundred yards farther out.
Why Energy Falls Faster Than Speed
Kinetic energy is proportional to mass times velocity squared. Because velocity is squared, a given percentage loss of speed produces a larger percentage loss of energy. A projectile that has lost 20 percent of its velocity has lost about 36 percent of its energy, so energy tables always decline more steeply than velocity tables for the same projectile.
The Role of Ballistic Coefficient
How well a projectile resists drag is summarized by its ballistic coefficient, which blends its mass, diameter, and shape. A higher ballistic coefficient means slower velocity loss and therefore more retained velocity and energy at every distance. This is why two projectiles leaving the muzzle at the same speed can arrive downrange with very different remaining performance.
Why These Values Are Tabulated
Retained-value columns let a reader compare designs on equal footing across a range card. Rather than judging by muzzle numbers alone, an analyst can see which projectile still carries useful speed and energy at the distance that matters, which is the heart of interpreting long-range behavior.
Worked Example
Consider a projectile leaving the muzzle at 2,800 feet per second and slowing to 2,000 feet per second at 500 yards. Its velocity has fallen by about 29 percent, but its energy has fallen by roughly 49 percent, because 2,000 squared over 2,800 squared is about 0.51. Nearly half the energy is gone even though most of the speed remains.
A Common Misconception
It is tempting to assume energy declines at the same pace as velocity, so a projectile at half its muzzle speed still has half its energy. Because energy depends on velocity squared, a projectile at half speed retains only about a quarter of its muzzle energy. Confusing the two leads readers to badly overestimate remaining performance at distance.