Ballistic knowledge–knowing how far your bullet, fired from your rifle in the local atmospheric conditions, will drop at different ranges–can spell the difference between a hit and a miss. If you hunt, you need to know the exact trajectory of your projectiles at given ranges so you can make a humane kill. If you shoot targets for fun or competition, you’ll also want to know exactly what your bullet will do beyond a couple of hundred yards, so you can make first-shot hits. Most importantly, in any shooting situation, you have to know exactly where your bullet will travel. A shot that inadvertently impacts the ground can skip and travel to unintended places.
There are two basic approaches to accurately predicting the vertical and horizontal path of your bullet once it leaves the muzzle. First, you can use a ballistic calculator app on a smartphone. Second, you can use a portable weather meter with ballistic calculation capability.
Ballistic Calculator Applications
Good ballistic apps are plentiful. The one I use, Ballistic AE, is available for iPhones, iPads, and iPod touch devices. (It’s not currently available for Android devices, but there are other apps that provide similar functionality, such as Applied Ballistics, that uses the same ballistics model available in the Kestrel weather meter that we’ll discuss in a minute.)
To oversimplify a bit, ballistic calculator applications calculate the drag models of various projectiles moving at different velocities. If you know the specific projectile you want to fire, and how fast your particular firearm launches it, you can predict with great accuracy the flight path of that bullet.
Most ballistic calculators require a key piece of information required for the drag model: the ballistic coefficient of the bullet itself. You can think of ballistic coefficient as a representation of how efficiently your bullet travels through the air. When you add current atmospheric conditions and starting velocity to the ballistic coefficient value, it’s possible to predict how the bullet will perform over distance.
Many ballistic apps like Ballistic AE maintain vast libraries of common bullet types and cartridge loads, so they know variables like ballistic coefficients and velocity. As a result, the user doesn’t necessarily have to research these obscure values. The apps will require additional user input including the current barometric pressure, altitude, and temperature before they can produce accurate trajectory tables. You’ll also have to input additional information about the height of your optic sight above the bore, zero range and other factors.
While ballistic calculators can predict the bullet path with great precision, they lack one important feature: the current atmospheric conditions. Many apps can leverage internal GPS capability and wireless data connections to estimate current meteorological conditions based on nearby locations, but they generally can’t tell you the exact conditions where you’re standing.
Once you fill in the blanks, the application will spit out a trajectory chart showing bullet performance at various distances. If you entered current wind information, the app will even show you lateral drift over distance so you can hold accordingly.
Ballistic Weather Meters
Ballistic apps are great, but they rely on a wireless data connection or manual input of current atmospheric conditions for best results. While that can provide a good indication of local conditions, it’s just that—an indication.
If you need to know the exact wind, temperature, altitude, barometric pressure, and humidity conditions where you are right now, then you’ll want a portable weather meter to provide input data for your ballistic app. Better yet, you can get a unit like the Kestrel Ballistic 4500NV Applied Ballistics Meter.
This solution has it all. The Kestrel includes a wind meter and internal compass. Together, they can automatically calculate the crosswind component based on the direction of your shot. Barometric pressure, temperature, and humidity sensors provide other necessary environmental information.
What makes this unit tick is the built-in software for calculation of bullet trajectory and drift. Input up to 16 loads with ballistic coefficient, bullet weight, bullet length, and velocity information, and the unit will combine current atmospheric measurements with ballistic performance data to accurately calculate the flight path.
I’ve been testing the Kestrel with a specific load I constructed for my Weatherby .257 Magnum Vanguard rifle. The 100-grain Barnes TTSX bullet has a measured velocity of of 3,483 feet per second from my Vanguard rifle. From Barnes, I know that this bullet has a ballistic coefficient value of .357. I enter this information into the Kestrel, along with velocity, bullet weight, bullet length, and bullet diameter. Then, I allow the unit to take a snapshot of current atmospheric and wind conditions. A fraction of a second later, the Kestrel displays a shooting solution based on the yardage I select. The Kestrel provides not only elevation data to account for bullet drop, but windage adjustment based on the current wind strength and direction vector. It’s somewhat of a miracle.
In my experience with both ballistic computer apps and the Kestrel 4500 NV, I’ve found that there’s a place for each. While the units perform similar functions, there are enough differences to justify keeping both handy. I find I use the Ballistic AE app for planning. The larger screens and easier data input help me model “what if” scenarios so I can make informed zeroing decisions before I ever leave home. When deciding whether to set the zero on a particular rifle to 50, 100, or 200 yards, I can easily evaluate the entire flight path of the bullet with different zero distance settings. On the other hand, the Kestrel is designed for field use, and there’s no need to worry about data connectivity issues you might have with smartphones.