Do Temperature Changes Affect .22 WMR Terminal Ballistics?

Effects on Expansion

Temperature fluctuations can influence the expansion of .22 WMR bullets, particularly in colder conditions. A drop of 20°F (11°C) below freezing can result in 10-15% less expansion, while an increase of 20°F (11°C) above freezing may result in 10-15% more expansion. This effect is more pronounced with hollow-point bullets, which rely on their jackets to expand upon impact.

Impact on Accuracy

Temperature changes can also affect the accuracy of .22 WMR rifles. In extreme cold, the rifle’s barrel may contract, causing the bullet to strike the target slightly off-center. Conversely, in hot temperatures, the barrel may expand, resulting in a slightly off-center impact. This effect is typically more noticeable in bolt-action rifles, where the bolt can heat or cool the barrel during firing. To mitigate this, shooters can use a cold barrel or a rifle with a free-floating barrel to minimize temperature-related accuracy issues.

Practical Considerations

When hunting predators with a .22 WMR rifle, it’s essential to consider the temperature and its potential effects on terminal ballistics. In extremely cold conditions, a rifle with a muzzle brake can help dissipate heat and reduce the effects of barrel contraction. Shooters can also use a high-quality scope with a bullet drop compensation reticle to account for temperature-related accuracy issues. Additionally, using a bullet with a thicker jacket can help maintain expansion in colder temperatures.