Build a better mousetrap, and the world will beat a path to your door.

In the realm of ballistic calculators, Hornady® has built that better mousetrap, but you don’t need to beat a path anywhere. Simply download it at the App Store or Google Play.

And you can save your cheese. This mousetrap is free.

So, what makes the Hornady Ballistic Calculator with 4DOF® so different from standard ballistic coefficient (BC) based calculators? Oh, a few things — about 434 of them.

“There are 437 unique values in every 4DOF bullet file specific to that one bullet,” said Jayden Quinlan, Hornady senior ballistician.

“There are BC-based programs that will calculate just based on a BC. Most of them will have a BC input, a bullet weight and a bullet diameter input,” he said. “So that program knows three things about your bullet versus 437 things. Some programs use custom models to handle predictions better than a simple BC value, but they lack the ability to correctly account for projectile dynamic responses in flight.”

Four Degrees of Freedom

The name 4DOF refers to Degrees of Freedom, as in freedom of movement of your bullet. BC-based programs provide predictions for three degrees of freedom:

• Elevation
• Windage
• Range

But the 4DOF calculator adds a fourth degree — angle of attack.

“At a basic level, the difference between the Hornady 4DOF and most other calculators is that the 4DOF has a bullet in it, and it’s predicting the angle of that bullet relative to the flight path,” Quinlan said. “To correctly account for the effects of wind, aerodynamic jump, and spin drift, the angle of attack is critical.”

“It’s not just a generic bullet,” said Seth Swerczek, marketing communications manager. “It’s the specific bullet that you’re actually shooting.”

A BC-based calculator is simple and doesn’t require a lot of inputs.

“They work really well in some circumstances,” Quinlan said, “and in others, they don’t.”

The 4DOF, on the other hand, is a modified point mass solver, and making it work took a lot more than a slide rule and pocket calculator.

It all begins with Doppler

“When we got our Doppler radar about 10 years ago, we finally had a piece of equipment that was capable of measuring the things required to do the really advanced calculations,” Quinlan said.

Firing a bullet over Doppler radar is the first of three steps in creating a 4DOF bullet file.

“Once that part is done, we’ve measured the drag of the bullet in its entire flight path through all kinds of different barrels, guns, loads and stuff like that,” he said. “The next step is to correctly model the bullet and its shapes and layouts.”

They not only measure the outside of the bullet but also cut it in half and measure the inside.

“We build, essentially, a software model of what that bullet’s measurements were,” Quinlan said, “and then we assign the different densities that are correlated to those materials.”

Step 3 involves a spark range, which takes multiple images of a bullet in flight from above and the side.

“You can record the bullet’s position in six different degrees of freedom, which are the six ways a bullet can move,” he said. “The government’s done all that work. They have this huge database of projectiles.”

Hornady compares specific projectiles to ones in the database and brings all the information from those three steps together in its 4DOF bullet file. That results in 437 unique values as opposed to three in a BC-based system.

Special features add to versatility

“It’s clear that the computational power of the 4DOF calculator is vastly more complex than a simple BC-based calculator,” Swerczek said.

A variety of other features also make 4DOF the superior system. One is its axial form factor, which limits adjustments to trajectory solutions provided by the calculator.

“That’s the adjustment up or down within a 10% limit,” Quinlan said. “We limit you so you can’t take it way out of context inadvertently adjusting the wrong input to calibrate your solution to what you are observing on target.”

The 4DOF also offers zero angle in addition to a traditional zero range. Zero range is the distance at which the bullet crosses the line of sight and will change in different conditions such as wind, shooting angle, and environmental conditions.

“If you’re trying to put that first round on target every single time and you’re running zero range, you’re doing yourself a disservice,” Swerczek said.

“Zero angle calculates all the trajectories based off the launch angle of the barrel, which is how it actually works,” Quinlan said.

The app allows the user to create an account with a log-in, which you can access from your phone or any other device with 4DOF. One login can be used on multiple devices at the same time making it a great tool for instructors.

“Everything that you do in that app is going to be tied to that log-in account and saved into the cloud,” Quinlan said. “Any profiles you build, any results you save, the favorite files, those are tied to that email log-in.”

Store your hand-loading recipes

A shooter can choose not only Hornady bullets but many competitor bullets from the library and input case, primer, cartridge overall length, charge weight and powders.

“If you’re a reloader or a hand loader and you have your own recipe, you can record all that stuff in here,” Quinlan said.

You can input rifle information such as muzzle velocity, barrel twist and bore diameter in your favorites.

“If you’re going to shoot multiple bullet types or different loads through one rifle, you can clone that favorite,” he said. “Then you just change whatever is pertinent.”

Environmental conditions can be obtained from a weather meter paired with 4DOF via Bluetooth or inputted manually.

With add-ons that cost a small fee, shooters can create multiple heads-up displays (HUDs) for different locations and custom range cards for every stage of a match. The group analysis feature allows for quick and easy analysis and aids in setting zero angle.

The 4DOF also includes a BC calculator for shorter-range situations in which it works well. All Hornady bullets and ammo are included on the BC calculator and custom BC inputs can be added for any bullet not in the library.

“If you start to see problems with the system you’ve been using — you’re hitting a little higher, you’re hitting a little lower, your wind calcs are off — go see what 4DOF says,” Quinlan said.

“Nobody likes to chase their tail, and your time is also worth something,” Swerczek said. “4DOF just makes it a better mousetrap all the way around.”

For more information on the Hornady Ballistics App with 4DOF®, watch these podcast videos for an in-depth discussion on why it is superior to BC-based ballistic calculators.