1. What is Sectional Density?

Sectional Density (SD) is a ballistic calculation that represents the ratio of a projectile's mass to its cross-sectional area. It's a key factor in determining a bullet's ability to overcome air resistance and maintain velocity and energy downrange.

2. How Does the Calculator Work?

The calculator uses the Sectional Density formula:

Where:

• \( mass \) — Bullet weight in grains
• \( caliber \) — Bullet diameter in inches

Explanation: The formula calculates how much mass is concentrated in a given cross-sectional area, which influences penetration capability and ballistic efficiency.

3. Importance of Sectional Density

Details: Higher sectional density typically results in better penetration, retained velocity, and energy transfer at longer ranges. It's particularly important for hunting applications where deep penetration is desired.

4. Using the Calculator

Tips: Enter the bullet mass in grains and caliber in inches. Both values must be greater than zero for accurate calculation.

5. Frequently Asked Questions (FAQ)

Q1: What is a good sectional density value?
A: For big game hunting, SD values above 0.250 are generally considered good, with values above 0.300 being excellent for deep penetration.

Q2: Does sectional density affect accuracy?
A: While SD primarily affects penetration and retained energy, it can indirectly influence accuracy through its effect on ballistic coefficient and wind resistance.

Q3: How does sectional density relate to ballistic coefficient?
A: Sectional density is a component of ballistic coefficient (BC). BC = SD / form factor, where form factor accounts for the bullet's shape.

Q4: Can two bullets with different weights have the same SD?
A: Yes, if a heavier bullet has a larger diameter, it could potentially have the same SD as a lighter, smaller caliber bullet.

Q5: Why is SD measured in lb/in²?
A: The units result from dividing mass (in pounds, where 7000 grains = 1 lb) by area (in square inches), giving lb/in² as the standard unit.