Weather and other environmental conditions can play havoc with your accuracy when shooting at longer distances, and knowing how to effectively compensate is a must.
Seasoned shooters know what outdoor factors can do to affect the trajectory of bullets, and ideally be able to make the right call to help offset. Even then there are always a variety of elements in-play that can mess-up a beautifully lined-up shot, but thankfully there are a number of tools that can help with specific calculations. Between temperature, altitude, wind, precipitation and whatever else you need to think about to hit that target or make an ethical kill (if you can hit it at all), there’s a LOT going on.
Typically, environmental conditions don’t affect accuracy much at all inside of 100 yards. The aggregate effect is much more pronounced over longer distances, as it would be for normal drop behavior. There is an actual science to all of this and there is no shortage of charts, gauges and now apps available (discussed below) that provide the data required to make accurate shots, even in extreme weather. In some cases though, how trajectory is impacted can seem counter-intuitive. For all that we now know about the subject, there are still some common myths and misconceptions that can make this confusing (especially for new shooters). Although we do have the benefit of technology to help the process, having a basic understanding of the fundamentals can’t hurt. If your mobile runs out of battery at the wrong time, you may be out of luck.
Before you consider how the conditions may affect the flight of your bullets, you should have a good idea of what you’re shooting exactly and how the rounds will react under different circumstances. Not all ammo is created equal and you have to understand the nuances of the load/powder type, shape, drag, weight and velocity. Ammo manufacturers typically test at set standards for elevation, humidity, temperature and barometric pressure. However, shooting at extremes in temperature may affect your burn rate and velocity, so a temperature-stable or better-balanced powder can help.
This is one of those elements that causes some confusion. There is a general perception that, even though it rises, hot air is somehow ‘heavier’ than cold air, especially when you throw in some humidity. You’ve probably heard or even said the phrase yourself that the ‘air is so thick that you could cut it with a knife’. That’s just how it feels. Turns out that the opposite is true.
Cold air is actually more dense due to the fact that its molecules move more slowly and they are in closer proximity to one another. This effect creates more drag on projectiles, causing them to move slower and drop more distinctly. Warm air on the other hand has fewer, faster moving molecules and will create less drag. A good way to remember the rule is to imagine that heat rises and so does your impact. As the temperature sinks, so will your shot.
Although this does play a role in longer-range ballistics, the effect is so small that you normally don’t need to consider it much. Humid air is less dense than dry air (again, it doesn’t feel like it) and will make for less drag on bullets as they travel.
Essentially, as the altitude increases, air density decreases and it becomes ‘thinner’. This reduces the drag on projectiles and provides for a flatter trajectory and less drop. In this case, your impact will be high unless you account or it. The opposite effect occurs closer to sea level, with more air resistance coming into play and lower strikes occurring if no adjustments are made.
There are definitely differences of opinion on this one. Some contend that rain or snow can potentially hit a bullet in flight from above and cause it to slow or deviate from its path and consequently strike lower. Others say that it’s impossible for a bullet to be struck in this manner due to its speed and the resulting shock wave that it produces as it travels. There is also a theory that the bullet’s shockwave may be compromised somehow by blowing ‘through’ the energy of raindrops, thus creating more drag. There have been many tests conducted, including those utilizing ultra high-speed photography, but the conclusions all seem a little vague.
One thing that is true is that bullets tend to strike higher than normal when it’s raining. Again, sounds counter-intuitive, right? The answer lies in the fact that in poor weather, there is lower barometric pressure (ie. air pressure) with less density and less drag or resistance. The fact is that if it’s raining, your impacts will likely be higher.
This is another one of those factors that creates some debate on how it affects accuracy. When you consider headwinds, tailwinds, crosswinds and any verticals that may occur in hilly terrain, there is no doubt that trajectory is affected to some extent. Again, it’s the how and by how much that’s the question.
There are fundamentals for accounting for drift of course and they’ve been around forever. If you go down the rabbit hole of theories though, that’s when you find some differences of opinion (and semantics). Some refer to ‘drift’ and ‘deflection’ as the same, while others claim that they’re two different things altogether. Does a crosswind ‘push’ the projectile laterally across its path or does it ‘deflect’ or crab to a new directional vector? And what about spin drift on top of that? In any case, there is enough data available to help compensate. Experience also counts for a lot too.
Apps & Gauges
As mentioned above, aside from the more traditional charts and gauges (and good old shooter know-how), there are many mobile phone apps and higher-tech devices on the market that are an absolute must to help account for all of the various environmental conditions that you’ll have to contend with. Doing the ‘math’ on all of this, especially as a new shooter, can be daunting at best and you’ll always want to give yourself the best opportunity for making successful shots.
The great thing about these modern ballistic calculators is that they not only account for atmospheric conditions, but some also provide data on thousands of commercial projectile types and factory loads. Taking the guesswork out of calculating for accuracy is a real bonus.
It’s not a question of if your ballistics will be affected by the environment, but by how much.
Understanding all of the overlapping elements and variables that affect your shots will help to ensure a better overall experience.
Sign up for K-Var’s weekly newsletter and discounts here.