How Do Environmental Factors Affect My Rifle's Zero?

Temperature and Humidity

Temperature and humidity changes can affect the expansion and contraction of rifle components, such as the barrel, stock, and optics. For every 20-degree change in temperature, a rifle’s barrel can expand or contract by approximately 0.005 inches. To adjust for this, aim to re-zero your rifle every 20-30 degrees of temperature change. For example, if you re-zero at 60 degrees Fahrenheit, you may need to re-zero again at 80 degrees to account for the expansion.

Atmospheric Pressure and Elevation

Changes in atmospheric pressure and elevation can also impact your rifle’s zero. As elevation increases, air pressure decreases, causing projectiles to travel faster and potentially affecting trajectory. For every 1,000 feet of elevation gain, the ballistic coefficient of a rifle round may increase by approximately 1-2%. To compensate, you can use a ballistic calculator or consult a ballistics chart to determine the correct zero for your specific rifle and hunting location.

Wind and Barometric Pressure

Wind and barometric pressure changes can also impact your rifle’s zero. Wind deflection can cause your bullet to deviate from its intended trajectory, while changes in barometric pressure can affect the bullet’s flight path. To account for wind deflection, use a ballistic calculator or consult a wind deflection chart to determine the correct wind correction for your specific rifle and hunting conditions.