See the signs and know the solutions when dealing with rifle scopes and extremely hot weather.
A while back, we published an article called "Rifle Scopes and Extremely Cold Weather.” With Death Valley experiencing near-record heat that has recently touched 130 degrees, it's time to further the discussion on weather and rifle scopes to also include extreme heat.
Are Rifle Scopes Built for Extremely Hot Weather?
The quick answer is "yes." But all metal expands and contracts in extreme temperatures. I think it's safe to say, however, that our human bodies would suffer debilitating effects from extreme heat before our rifle scope. While the physical integrity of a rifle scope will likely survive hot temperatures, it is important to mention that the point of impact can certainly change.
It may seem like your point of impact rises on sun-scorched days. In many cases, the zero on the rifle has not shifted, but the increased mirage causes the desired target to appear slightly higher than it actually is. Even when no environmental mirage occurs, heat rising from a rifle barrel can cause very small amounts of mirage to appear in the field of view.
While it is possible that an older scope could experience a slightly shifting zero, scopes of the modern age are built according to very high standards and expectations, and the odds of a shifting zero are low.
Scopes are mostly protected from heat, but a rifle’s barrel may experience worsening performance from overheating. Accuracy could be negatively affected by a barrel that has overheated, and consistent shooting through an overheated barrel can significantly reduce its shelf life.
Risks Rifle Scopes and Extremely Hot Weather
While scopes - as well as most optics - are physically able to withstand hot weather, the real risk to preserving quality is the rapid introduction of opposite extremes. If a scope is cold and then introduced to very high temperatures or vice versa, internal damage could occur after repeated cases. Internal seals could theoretically crack after enough instances and affect the internal gas purging, though we have never heard of a case when that has happened.
In some cases, a scope could also experience fogging when temperatures rise too quickly. Fogging is caused by moisture held inside the tube.
When a scope is cold and is then introduced to warmer temperatures, the internal gas expands and creates condensation. While this could certainly occur, most modern, higher-quality scopes are purged of air inside the tube and replaced with a compound like argon in the case of those made of the top quality.
Argon is inert and does not easily bond with other elements, which prevents condensation from forming. If someone experiences fogging with a gas-purged scope, a larger problem, such as a damaged scope, may be apparent. For the most part, fogging from extreme heat will only be experienced by shooters using lower-quality optics.
Jon LaCorte discusses the advantages of argon gas.
It is also important to remember that a scope's internal electronics could be damaged by extreme heat. If the temperatures outside become too hot, there is the potential for an electrical short or malfunction. Higher-end scopes with larger lenses and more features will absorb more heat compared to their smaller counterparts.
Finally, drastic shifts in weather can affect the batteries used in night vision or electronic scopes with illuminated reticles. Depending on the battery type and manufacturer, extreme cold temperatures can decrease battery life and performance. Conversely, extremely hot temperatures can cause a battery to overheat and potentially damage the scope. While this is highly unlikely, it is theoretically a possibility.
The extreme heat needed for each of these risks to become reality would be much more likely to come from a rifle left inside a secondary environment, like inside of a trunk, than in an outdoor location. In fact, the most common risk shooters experience is touching their scope after it becomes too hot.
Protecting Your Scope from Hot Weather
In order to protect your scope from hot weather, it is important to take a few precautionary measures. As mentioned, it is best to only buy scopes that have been purged with inert gasses, such as argon. Additionally, storing your rifle in an insulated case can help prevent extreme heat from damaging the optics. When shooting in direct sunlight, use a scope cover or drape a rag over your tube to keep the sun from being directly absorbed.
If you suspect that your scope is becoming too hot, it's a good idea to give it a break and cool it off for at least 15 minutes before using it again. How hot is too hot? If you are unable to maintain constant contact without feeling a burn, it might be time to cover it up or move to the shade.
Across the globe, this summer has been one of the hottest on record. While it’s unlikely most shooters will ever experience temperatures that could damage their optics, their personal performance and shooting experience are more likely to melt from rising mercury. With a small amount of preparation and a big thermos of cold water, the heat should never prevent you from enjoying another day in the field.
