Does Altitude Impact Handloading and Ballistics?

Effects on Ammunition Performance

Altitude affects ammunition performance by altering the rate at which propellant burns. At higher elevations, atmospheric pressure is lower, causing the propellant to burn faster and potentially resulting in increased chamber pressures. This can be mitigated by reducing propellant charges by 3-5 grains per 1,000 feet of altitude, as recommended by the Hodgdon Reloading Manual.

Ballistic Calculations

Ballistic tables and calculators should take into account the altitude when predicting bullet trajectory and impact. A 1,000-foot increase in altitude can result in a 1-2% increase in bullet velocity, affecting bullet drop and wind deflection. Hunters should use ballistics software or consult with a ballistician to ensure accurate calculations at their specific elevation.

Reloading for Altitude

When reloading for altitude, it’s essential to consider the type of rifle and cartridge being used. For example, a .300 Winchester Magnum may require a 5-grain reduction in propellant charge at 10,000 feet, while a .308 Winchester may require only a 2-grain reduction. Consult the reloading manual for specific recommendations and always follow safe reloading practices.