A seasoned hunter in the Colorado Rockies, poised for the perfect shot at a prized elk. The crisp mountain air bites at his cheeks as he squeezes the trigger, confident in his aim. But the bullet strikes low, too low, and kicks up a splatter of snow. The elk bounds away, leaving the hunter puzzled and empty-handed. On the other side of the planet, the military sniper on a critical mission in the Afghan highlands. Despite meticulous preparation, his usually pinpoint accuracy is off by inches at long range – inches that could mean the difference between mission success and failure. Even at the local shooting range, a competitive reloader finds his carefully tuned handloads performing erratically, throwing his match-winning aspirations into disarray. What do these scenarios have in common? They all demonstrate the often-underestimated impact of cold weather on ammo performance.

Cold Weather & Ammo Performance

As the mercury plummets, seasoned shooters know that cold weather brings a unique set of challenges to firearms performance. Perhaps nowhere is this more evident than in how low temperatures affect ammunition. From altered ballistics to potential malfunctions, cold weather can significantly impact your shooting experience. This article delves into the science behind these effects and offers practical advice for maintaining accuracy and reliability when the temperature drops.

How Cold Affects Propellants

Modern smokeless powders are made from complex chemical compounds, primarily nitrocellulose and sometimes nitroglycerin, among others. These compounds are engineered to burn at a controlled rate when ignited by the primer, producing a steady and predictable expansion of gases that drive the bullet down the barrel. The burn rate of the powder directly affects the pressure inside the chamber, the velocity of the bullet, and ultimately the accuracy of the shot. As temperatures drop, the chemical reaction that causes propellants to burn slows down and/or burns unevenly. This slower (or uneven) burn rate leads to lower chamber pressures and, consequently, reduced muzzle velocity. The result? Your bullets may impact lower on the target than expected.

Dr. Harold Vaughn, a renowned ballistician, notes in his book, Rifle Accuracy Facts, that some propellants can lose up to 50 feet per second in velocity for every 10°F drop in temperature. This might not seem significant for close-range shooting, but at distances of 300 yards or more, it can mean the difference between a hit and a miss.

Dense Air, Denser Problems

Cold air is denser than warm air. This increased density means that each cubic meter of cold air contains more air molecules compared to warm air. When a bullet travels through this denser medium, it encounters more resistance or drag. This drag affects the bullet’s trajectory and can have several implications for shooting accuracy. 

Ballistician Bryan Litz explains in his book Applied Ballistics for Long Range Shooting that for every 20°F drop in temperature, air density increases by about 2%. This might seem small, but it can have a noticeable impact on long-range trajectories. For example, 2% increase in air density can cause a measurable shift in the bullet’s point of impact, potentially altering the trajectory by several inches at 500 yards. A study by the U.S. Army points out: “If the last time your weapon was zeroed the temperature was 90°F and you’re now in freezing temperatures, your ammo could impact the target nine inches low at 300 meters due to temperature and air density.”

Cold Steel: Mechanical Considerations

Cold weather doesn’t just impact ballistics; it also affects the physical properties of both your ammunition and firearm. Low temperatures can cause ammunition components to become brittle and firearms to experience contraction and metal fatigue, leading to potential reliability issues.

Brass: Commonly used for cartridge cases, it can become more brittle at low temperatures due to reduced molecular activity. This increased brittleness can lead to cracking or breaking under stress, resulting in case head separations or split necks. Case head separations pose risks of firearm damage or injury, while split necks can cause poor chambering and inconsistent ignition, affecting accuracy and safety. This increased brittleness can happen especially in reloaded ammunition that’s been fired multiple times.

Primers: Essential for igniting the propellant, they also suffer in extreme cold. The explosive compounds in primers, such as lead styphnate or similar materials, are less reactive at low temperatures. As well, the chemical reactions necessary to generate the ignition spark slow down, making it harder for the primer to ignite reliably. The binders and stabilizers, like lead dioxide or styphnate, can become more viscous or even slightly solidify in very cold temperatures. Their decreased sensitivity can lead to potential misfires or hang fires, where ignition is delayed. 

Lubrication: Standard lubricants can thicken, reducing their effectiveness and causing sluggish operation or cycling issues in semi-automatic and automatic firearms. To counteract these problems, cold-weather lubricants are recommended, as they maintain their viscosity and performance in low temperatures.

Metal parts: Not ammunition specific, but it is important to also note that cold temperatures can cause the metal of a firearm’s barrel and action to contract, potentially altering its zero or causing fitment issues. As well, any moisture inside these parts can freeze, leading to jamming or malfunctions. Prolonged exposure to cold can also result in metal fatigue, making components more susceptible to wear and failure.

Strategies for Cold Weather Shooting

Given these challenges, what can shooters do to maintain performance in cold conditions? Some propellants are more stable across temperature ranges than others. For critical cold-weather applications, consider loads using propellants known for their temperature stability. 

When possible, keep your ammunition at a consistent temperature. Some competitive shooters use insulated ammunition carriers to maintain a stable temperature. For hunting or tactical situations, keeping spare ammunition in an inside pocket can help. If you’re shooting in significantly colder conditions than when you last zeroed your rifle, consider re-zeroing. This accounts for the changes in velocity and trajectory caused by the cold. In cold weather, clean your firearm more frequently and use cold-weather specific lubricants that maintain their viscosity at low temperatures. Hodgdon’s Extreme series of powders for reloaders, for example, is designed to maintain consistent velocities across a wide temperature range. Though not an endorsement, Lapua’s Center-X and CCI Ammunition’s Standard Velocity ammo (specifically their 22 LR at 40 grain) has been known to perform well in cold weather, though your experience may vary.

Conclusion

Cold weather presents unique challenges for ammunition performance, from altered ballistics to potential reliability issues. By understanding these effects and taking appropriate precautions, shooters can maintain accuracy and dependability even when the temperature drops. Whether you’re a competitive shooter, a hunter, or a professional who must perform in any condition, knowledge of how cold affects your ammunition is crucial for success when the mercury falls.

Remember, in the world of shooting, success often comes down to understanding and adapting to your environment. When it comes to cold weather, being prepared can mean the difference between a successful shot and a missed opportunity.