What Should I Know About Ballistic Coefficients for Bullets?

Understanding Ballistic Coefficients

Ballistic coefficients are essential for accurate long-range shooting, particularly with controlled expansion bullets. These bullets, designed to expand consistently upon impact, can benefit from a high BC to maintain their trajectory. A high BC indicates a bullet that will resist air resistance better, resulting in less wind deflection and bullet drop. For example, the Remington Core-Lokt Tipped has a BC of 0.455, while the Federal Premium Nosler Partition has a BC of 0.480. When choosing between these two bullets, the higher BC of the Federal Premium may make it a better option for long-range shots.

Calculating Ballistic Coefficients

Manufacturers measure BC values by launching a bullet through a wind tunnel, using a technique called the G7 method. This method calculates BC using the following formula: BC = (1 - (weight of the bullet in grains) / (diameter of the bullet in inches)^2) / (drag factor of the bullet). As a general rule, bullets with a high BC will have a smaller diameter, as they produce less air resistance. However, a higher BC does not always mean a smaller diameter, as some bullets are designed with unique shapes to achieve a high BC.

Using Ballistic Coefficients Effectively

When choosing bullets for long-range shooting, make sure to consider the manufacturer’s listed BC values. However, it’s also essential to understand that BC values can vary depending on the specific rifle and load used. For example, a bullet with a high BC in one rifle may have a lower BC in another. To effectively use BC values, consider the following factors: the bullet’s weight, diameter, and shape, as well as the rifle’s barrel length and twist rate. By considering these factors and the manufacturer’s listed BC values, you can make informed decisions about which bullets to use for your long-range shooting needs.