SD – Sectional Density

Sectional Density (SD) measures the bullet’s effectiveness on the target. It is calculated by considering the weight and diameter of the bullet. Terminal ballistics, which refers to the effect on the target, is directly related to the SD. Velocity and energy also play a crucial role in enhancing the bullet’s ability to achieve a more effective “knock-down” effect, as well as its ability to penetrate. Generally, bullets with higher sectional density are capable of penetrating deeper.

Sectional density is a crucial factor when selecting a hunting bullet. This is because, when all other variables remain equal, a bullet with a higher Sectional Density will have the following advantages:

  • It will lose less energy and speed while flying, making hitting the target more accurate and precise.
  • It will drop less on the way to the target, making it easier to hit a distant target.
  • It will penetrate more effectively into a target, resulting in a higher chance of hitting the target accurately.

Generally, sectional density estimates can help compare penetration performance. Bullets with similar sectional densities, propelled at similar velocities and exhibiting similar expansion percentages, tend to penetrate similar depths.

For instance, let’s consider the following examples:
.30 Calibre (.308″)
– 100gr, SD = .166
– 150gr, SD = .226
– 165gr, SD = .248

.264 (6.5mm) – 140gr, SD = .287

This information can be helpful for those interested in understanding the penetration potential of different bullets, especially when it comes to hunting or other shooting activities.