Coriolis Didn't Make You Miss

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When it comes to long-range shooting there are many factors that come into play to make consistent first-round impacts on targets. Modern technology has given us mini mobile computers in our cell phones that are capable of computing atmospheric conditions to make predicted bullet path models. These models are then computed to MOA and Milradian adjustments to dial into the scope for the proper trajectory including wind drift. Air temperature, barometric pressure and altitude are the most important factors we must apply as accurate data into the devices to predict a flight model. Many shooters have fallen victim to the idea that some factors play a larger part when in reality they are negligible in most situations and smaller mistakes are more likely to cause issues. You should always assume the guy behind the bolt and data entry is to blame for any issues that arise in the process. Check your data and re-engage to confirm.

Considering environmental conditions to add into computing these models can be confusing at first glance. Working with any ballistic solver app on your phone the results can vary from app to app when using the same atmospherics and bullet projectile and muzzle velocity. Each solver uses different algorithms to compute the predicted path of a bullet or uses different BC (ballistic coefficient) models leading to a different end result. Couple this with an inaccurate zero on the rifle and the shooter will start to question everything. When shooters start to miss targets they often resort to “truing the BC'' or changing the BC to alter the bullets flight path to correct for their misses. This will only fix a portion of the issue causing you to change the “bend” of the curve to impact the target at 800 yards, but now be 4” high at 400 yards and so on. The key to success is focusing on what matters for environmental conditions, entering accurate data, and using the proper solver to give you the best-predicted flight path.

Establish an Absolute Zero

I have no less than six ballistics solvers on my phone at this moment, but I primarily only use two apps for most of my shooting needs. Most solvers will be sufficient for hunting scenarios and distances inside 700yds but the varying solutions can start to fall off at distances beyond 1,000 yards. Choose an app that gives you the most reliable and repeatable data for your rifle that interfaces best for you. The first step to proving your app is accurate is making sure your rifle has a solid zero at 100 yards. This is beyond just a 3 shot group on a target. I prefer to use a minimum of 10 shots in two five-shot sessions to establish an absolute zero ensuring the group is centered up horizontally and vertically on the exact middle of the target. Three shots on a bullseye is not enough to determine an accurate zero down range and will cause issues with both wind and drop in your solver if not dialed in properly to start.

Rifle Data Entry for Solvers

Once your rifle is set with a solid zero you can now begin entering all your data from your rifle and cartridge into the solver. This starts with rifle data such as sight over bore height (the distance from the center of your bore to the center of your optic), barrel twist rate (twist rate per inch of barrel), barrel twist direction (left or right twist), zero range, muzzle velocity and bore diameter. This isn't a place to guess, you must enter the exact data from your rifle to get the best results. If you're unsure about your barrel twist info, a quick visit to a gunsmith can usually give you an accurate measure of the twist rate and direction. Factory rifle manufacturers usually have this information online or can give it over the phone by calling customer service.

For the muzzle velocity, always have a 10-shot string minimum to average out your muzzle velocity. A couple shots will not give you an accurate average to use in the solver and will lead to an overall larger dispersion down range for vertical impacts. Many shooters try to save ammunition and only shoot a few rounds then go straight out to 1,000 yards and wonder why they impacted low 4 shots, 3 shots on the plate, and 8 shots high. With all things being accurate in the data entry this is usually showing the muzzle velocity used is lower than the actual average. The muzzle velocity on the box is not an accurate measure either as your barrel may be shorter or longer resulting in different velocities. Purchasing an accurate chronograph is a must for those wanting to ensure this measurement is accurate.

Choose your Bullet Wisely

After the rifle's data is entered correctly and saved, you enter the projectile or bullet data in the solver. This solver should ask for projectile length, caliber, weight and BC (ballistic coefficient).

The bullet length can be measured easily with a pair of machinist calipers or searched for on the manufacturer's website. Most of the data needed on the bullet is easily found through the solver's bullet library but oftentimes newer bullets may not be added to the solver's data so you may need to enter the data manually. Ballistic coefficients can vary from manufacturer to manufacturer so be sure to enter the data they provide to start and avoid altering the BC when at all possible, this leads to inaccuracies down range that can cause you to chase your tail even more.

My personal favorite is Hornady’s 4DOF, a free app to download on your cellular device that has a separate portion of the solver built to alter drag models to help achieve a more accurate predicted bullet flight. This feature works extremely well and is without a doubt the most advanced solver on the market. While the bullet selection is mostly Hornady bullets, they are constantly adding new projectiles from every major manufacturer after they pass a series of tests through Doppler to establish an accurate BC. Many polymer tips used on hunting bullets deform under high temp during the bullets flight causing them to have erratic BCs. Hornady chooses to not add these projectiles as the data received is not reliable enough for the customer.

Now that you have all the data accurately entered on your rifle, ammunition and a solid zero you can rest assured that you are now at the proper place to verify your data at the range. Missing any portion of the above steps will lead to inaccurate results down range up to this point. Every solver needs environmental conditions in order to calculate the bullet's flight path accurately. This is where 90% of shooters start to go astray with Kestrels and other atmospheric reading devices giving too much data that doesn't always need to be considered. The only contributing factors you need to consider is air temperature, altitude or elevation above sea level and barometric pressure. These can be gathered from local weather stations on your phone or through a Kestrel, an atmospheric metering device. Just as important as the data you put in for your rifle and ammunition, this is no place to guess or approximate your current conditions.

When entering this data it is crucial it be taken as close to the time of the shot during a hunting situation and not gathered in the morning at home or base camp as temperature, elevation and pressure can change rapidly during the course of a hunt. This is where most hunters go wrong and gather inaccurate data prior to the moment of the shot and then blame environmental factors that didn't have an effect. Humidity for example, in most hunting scenarios is negligible under 1000 yards when the humidity is set at 50% as a default. It will not cause you to miss a deer at 600 yards ever, regardless of what you set it to and what the actual humidity measures. When you stretch out shooting to a mile or more on a small target with a precision rifle, it may start to become a visible factor, but leaving it set at 50% in most scenarios will get you on target every time, assuming the other data is correct.

Environmentals

Coriolis is the earth's rotational spin, forcing air to the right in the northern hemisphere and is often overutilized in most hunting and shooting scenarios at long range. Additionally, the earth rising and falling on its center axis if you're shooting east to west or west to east has minimal to no effect on a high BC bullet's flight path inside 1,000 yards but becomes a factor beyond 1,000 yards the longer the bullet flight time the more the effect. When shooting at extreme distances with longer bullet flight time, the bullet drifts right when shooting North. When shooting towards the East the bullet will impact high and if fired to the West it will impact low. Hollywood really hit this one hard in the movie “Shooter” in the scene where Mark Wahlberg talks about all the factors a shooter has to consider when taking an extremely long-range shot for a first round impact. For everyone else, it's a moot point that shouldn't even fall into your consideration for hunting applications unless you're shooting prairie dogs with a .308 Win at 1 mile.

Density altitude is a measure of air density at a given location above sea level. Most ballistic calculators give the option for DA (Density Altitude) and/or Temperature with Elevation. If you're unfamiliar with DA you can always find your temperature and elevation with your phone on a weather app. When it comes to DA, you'll want a Kestrel device to measure the current DA for data entry which is easily read off the device. Either one will give you an accurate prediction of the bullets flight path however both need to be accurately entered. You have some room for error being around +/- 5 degrees in temp and +/- 500 ft elevation with DA being around +/-500ft for the most accurate prediction. Keep in mind, good data in equates to good data out. Although this process may sound too scientific, these principles are crucial to keeping you on target when shooting at long range and become more important the longer the bullet is in flight. For most hunting scenarios under 500 yds you can get away with rougher data entry for atmospherics if your rifle has a solid zero and the muzzle velocity is accurate. A better plan of attack is to keep your data accurate at all times to ensure you're ready for whatever the mountain throws at you this fall. Keep it simple and establish accurate data for your solver and you will hit more targets and be more successful in the field.

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