Temperatures are rising and it’s time to be aware of what that heat can do to your weapons and your ammo. Aside from the basic safety practices that help to keep you and those around you safe – what and how you shoot will dictate how much attention you need to pay to the warmer weather.It’s one thing to simply want tight groups at the range, but the stakes get a little higher with making a difficult shot while hunting, and certainly more so with military or law enforcement applications.
Your Gun in the Sun
Let’s assume that you won’t just leave your weapon baking in the direct sunlight on a regular basis. Like most things, heat and UV rays aren’t your gear’s best friend and they can affect function and contribute to additional wear over time. Although most modern firearms are very durable, consistent high ambient temperatures can lead to faster parts and bore degradation. This typically is more of a long-term effect though. Performance can also be impacted depending on what you’re shooting, the barrel length and the rate of fire. Your barrel heats up like crazy as it is, and will stay hotter longer in warmer weather (what a surprise) and potentially flex more. The heating effect will be amplified with the use of sound suppressors as well. You’ll probably notice some issues your sighting/optics as a result.
There are some measures that you can take to help offset the heat and are probably more important if you actually live in a warm climate. These would include the variety of barrel flutes, fins, sinks and other heat dissipaters that are available on the market. They can be effective and it will depend on preference, your weapon type and shooting conditions. There are also fixed shades and mirage shields etc. but these are really only practical for stationery range shooting.
One other thing to consider is your regular gun maintenance. Lubrication tends to burn-off faster in the heat and conditions can be dusty. Make sure to be diligent with your routine.
Unlike firearms, your ammunition and its performance is likely to be more affected by hot conditions. Ammo heats up very quickly in the sun or in high temperature environments, including the trunk of your car. As a general rule, a higher propellant temperature will cause it to burn faster, producing more pressure and a higher projectile velocity. This would normally raise your POI, but you also have to consider distance, sighting changes and how your barrel acts in the heat. Your shots may end up missing in other directions as well. The ammo case material, its thickness and the type of powder used will also affect its sensitivity.
From a safety standpoint, the added heat can increase the likelihood of ammo failures or malfunctions (some catastrophic) while in the weapon. This can obviously be highly dangerous. Modern ammunition isn’t going to self-combust due to reasonably high environmental temperatures, but ignition issues are another story.
So let’s try and avoid direct sunlight (including mags) where possible and be sure to rotate your stock if it ends up spending a lot of time in a hot vehicle or garage.
It’s Not the Heat…
High humidity can often follow with increased temperatures depending on your locale. Like high temps, humid air will tend to raise your POI since it is less dense. What? Despite the fact that humid air feels ‘thicker’ and that you could cut it with a knife, the projectile will actually travel easier and with less drag. There are some general rules of thumb around the MOA (Minute of Angle) changes vs. variations in humidity, but they are guidelines only. You’ll have to use a little trial-&-error here
It’s not rocket science. Where possible, keep your gear cool – and like any change in season or environment, it’s always a good plan to re-zero before you shoot.
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