Quick Answer
Weather conditions significantly impact .308 ammunition performance, with temperature and humidity affecting bullet expansion, velocity, and accuracy. In extreme conditions, performance can deviate by up to 20% from factory specifications. Hunters must understand these factors to optimize their shots.
Temperature’s Effect on Bullet Expansion
Temperature fluctuations can drastically alter bullet expansion, particularly in the .308 Winchester. At temperatures below 40°F (4°C), bullets tend to over-expand, while above 70°F (21°C), they may under-expand. This is because the bullet’s core material changes viscosity in response to temperature. For example, a 150-grain Hornady InterLock bullet at 40°F (4°C) may expand 15% more than at 70°F (21°C). Hunters must compensate by adjusting their shot placement to account for this variation.
Humidity’s Impact on Velocity and Accuracy
Humidity can also affect .308 ammunition performance, particularly in humid environments. High humidity can reduce bullet velocity by up to 10% due to increased air density. This can lead to decreased accuracy, as the bullet’s kinetic energy is reduced. Additionally, high humidity can cause the rifle’s barrel to rust or corrode, affecting accuracy. Hunters should take steps to maintain their rifle’s barrel, such as applying a rust inhibitor or using a barrel cover.
Field Considerations for Hunters
When hunting in variable weather conditions, hunters should be prepared to adjust their shot placement and technique accordingly. This may involve using a ballistic calculator to account for temperature and humidity effects on bullet trajectory. Hunters should also consider using a rifle with a adjustable gas system or a suppressed rifle to minimize the impact of weather on their shot. By understanding the effects of weather on .308 ammunition performance, hunters can increase their chances of a successful harvest.
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