Can Temperature Fluctuations Affect My Rifle’s Point of Impact?

Temperature Effects on Ammunition Expansion

When temperature changes, ammunition expansion can vary. For example, a .30-06 Springfield cartridge expanding 0.055 inches at 70°F (21°C) might expand 0.050 inches at 50°F (10°C) and 0.060 inches at 90°F (32°C). This difference can result in a 0.010 to 0.015 inch variation in bullet diameter, which can significantly affect your rifle’s point of impact.

Understanding Bullet Expansion and Temperature

Most commercial hunting bullets expand at temperatures between 45°F (7°C) and 85°F (29°C). However, extreme temperatures, such as those below -20°F (-29°C) or above 95°F (35°C), can alter bullet expansion, leading to inconsistent accuracy. When hunting in extreme temperatures, use specialty ammunition designed for those conditions.

Zeroing Your Rifle for Temperature Fluctuations

To minimize the effects of temperature on your rifle’s point of impact, zero your rifle at the average temperature you expect to hunt in. For example, if you plan to hunt in temperatures ranging from 40°F (4°C) to 70°F (21°C), zero your rifle at 50°F (10°C). Then, make adjustments for the temperature you’re hunting in. A general rule of thumb is to add 1-2 MOA (minutes of angle) for every 20°F (11°C) drop in temperature.