Quick Answer
Factory loads are affected by environmental factors such as temperature, humidity, and altitude, which can alter their performance. This is due to changes in the bullet's expansion, velocity, and trajectory, ultimately impacting accuracy and effectiveness.
Environmental Factors Affecting Factory Loads
Temperature Effects on Expansion
Temperature is the most significant environmental factor affecting factory loads. A rise in temperature can cause bullets to expand more than expected, leading to over-penetration or loss of kinetic energy. Conversely, a drop in temperature can cause bullets to expand less, resulting in under-penetration or a loss of stopping power. For example, a 9mm Luger cartridge may expand from 0.355 to 0.440 inches when fired at a temperature of 80°F (27°C), but expand from 0.355 to only 0.395 inches when fired at 40°F (4°C).
Altitude’s Impact on Trajectory
Altitude affects the trajectory of factory loads due to the decrease in air density. At higher elevations, bullets travel farther and drop less than at sea level. This is because the lower air pressure and temperature at high elevations result in less air resistance, allowing bullets to fly flatter and farther. For instance, a 5,000-foot (1,524-meter) elevation gain can result in a 10-15% increase in bullet trajectory, making it essential to adjust point of aim accordingly.
Humidity’s Influence on Velocity
Humidity affects the velocity of factory loads due to the increase in air pressure. High humidity can slow down bullet velocity, while low humidity can increase it. This is because the air pressure increases with humidity, resulting in more air resistance, which slows down the bullet. For example, a 90% relative humidity can result in a 10-15% decrease in bullet velocity, while a 30% relative humidity can result in a 5-10% increase.
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