Quick Answer
Weather conditions can affect the performance of both factory and handloaded ammunition, but handloads are more susceptible to variations in temperature and humidity due to their custom composition.
Temperature and Pressure
When temperatures fluctuate, the expansion and contraction of the cartridge case can affect the performance of handloaded ammunition. Factory ammo, on the other hand, is manufactured to withstand a wider range of temperatures. In extreme heat, factory ammo may experience a slight decrease in accuracy due to the relaxation of the cartridge case, while handloads can see a more significant drop in performance. At 100°F (38°C), handloads may lose 10-20 ft-lbs of energy compared to factory ammo.
Humidity and Moisture
High humidity can cause the propellant in handloads to become damp, leading to inconsistent ignition and reduced performance. Factory ammo, with its uniform propellant composition and sealed packaging, is less prone to moisture-related issues. In humid environments, handloads may see a 5-10% decrease in accuracy, while factory ammo may experience a negligible effect.
Case Sensitivity
Handloaded cartridges are more sensitive to case stretching and set-back, which can occur when exposed to extreme temperatures or humidity. This can result in reduced accuracy and inconsistent performance. To mitigate this, handloaders can use premium cases and employ techniques such as annealing to reduce case sensitivity.
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