Exterior Ballistics

I am often amused as I read some of the trifling on the Internet of the person who wants to buy their first rifle for the purpose of shooting 1,000 yards. This arbitrary distance seems to have become the standard for being an expert shooter. The homemade sniper for some sort of future zombie attacks. Shooting 1,000 yards, or any long distance, consistently and with repeatable accuracy and precision is artwork and requires a lot of practice. It is the understanding of physics, mathematics, and the second of four ballistic studies, exterior ballistics. It is an in-depth of knowledge of what a bullet, when released from the cartridge and muzzle, can and most importantly cannot do.

However, it is not undo-able at that range or farther, if you are willing to study, practice, and spend the time and money to learn to do so. Nevertheless, keep in mind that if I go buy a baseball bat today, I will not be hitting like Josh Hamilton, today, tomorrow and most likely ever. Even with the willingness, desire, practice, and all the money in the world it does take talent that I do not possess. Shooting is the same way, regardless of your skills on the video console. However, do not become discouraged. With some dedication and willingness to study and understand exterior ballistics, who knows? When the bullet exits the barrel, you are done with your job as the shooter and physics now takes over. We will look briefly at some of those factors that act on the bullet and the science of exterior ballistics. Then perhaps, with further study, you can become the best shooter that your talent will allow.

Bullet Flight Path

First, the typical rifle bullet does not appear to leave the barrel parallel to the ground. It can actually appear to leave the barrel at an upward angle; this is the Angle of Site (AOS). The Angle of Site of the bore is NOT the Line of Sight (LOS) of the scope or the rifle sights. Notice we are talking about two different ideas.

It is essential, to know when talking about the trajectory of a bullet, that a bullet will not defy gravity. The projectile begins to drop as soon as it leaves the muzzle. The appearance of the rise of the bullet is in the sights only and is due to the angle of the muzzle. The bullet appears to defy gravity but will immediately fall earthward upon exit of the muzzle. Under the influence of a uniform gravitational pull, a parabolic, not a true parabola but flatter, path is the trajectory of the bullet.

The next principle that affects the bullet is air resistance. Drag is the affect of air on the bullet. Vector is altered even further once it leaves the muzzle due to just air, not wind. We will cover that principle later. A shot taken at 5,280 feet of altitude and no humidity will encounter less air resistance, than a shot taken at sea level with considerable humidity. Even the time of year can drastically affect the flight of the bullet in these two locations.

Sonic Barrier – Bullet

Now that we have dealt with gravity and air, another physical principle comes into play. When the bullet reaches a velocity of 1,120 fps it becomes supersonic. Supersonic is faster than the speed of sound and anything traveling at that speed creates a shock wave as it breaks the barrier. A true physical barrier acts on bullets, planes, or anything moving at that speed.

Sonic Barrier – FA-18

At this stage, the bullet has contended with gravity, air, humidity and even a physical barrier, the shock wave on its flight to the target. We are not done yet. Another major factor comes into play to get our bullet on target, wind. Ballistically speaking gravity, the up and down trajectory, is called elevation and is referred to as Drop. The effect of wind, the left and right trajectory, is Drift.

When you consider Drift, there are innumerable variables. Is the wind the same at the muzzle, mid-flight, and at the target? At greater distances, wind changes can occur many times along the fight path in numerous directions. Confirming the speed and angle of the wind is vital. The Drift increases four times when you double the range. Heavier bullets tend to deal with crosswinds better than smaller ballistic coefficient calibers but will have more Drag. At what speed is the bullet traveling? Subsonic bullets are less affected by wind. Wind has a drastic affect on bullets at any distance, as it is amplified air, therefore amplified Drag or Drift.

Finally, the bullet in and of itself plays on the trajectory of fight. Some bullets are designed to shoot flat and long, others to tumble or yaw, then there is supersonic or subsonic velocity, it goes on endlessly. There are any number of differentials that a bullet is comprised of depending on the chosen target. The bullet alone is a study in trajectory that requires dedicated learning for repeatable results. One could spend a lifetime looking for that perfect projectile.

Repeatable AND Consistent

Repeatable and consistent results, is the goal of anyone trying to master the art of shooting. Whether at paper 20 yards away, that prize Elk at 900 yards, or the soldier in the field shooting at distances determined by a target well beyond 1,000 yards that may be shooting back, it all comes down to repeatable and consistent results. A strong grasp on the concepts of exterior ballistics is not optional if you want to be an artist.

The Mission of Cheaper Than Dirt!'s blog, The Shooter's Log, is to provide information—not opinions—to our customers and the shooting community. We want you, our readers, to be able to make informed decisions. The information provided here does not represent the views of Cheaper Than Dirt!

Comments (3)

  1. Among the things to throw into the mix are bolt action or semi action. I have found with the average deer hunting rifel, keep shots at 300 yards and below if it is a semi auto. If it is a bolt (or lever) action then you can go a bit farther for the average shooter. Those 1000 yard shots with the standard hunting rifel are rare, lucky and unnessary. I have a son that was a USMC sniper and those long shots are better left to guys like him, the professionals. If you want to attempt them get a bolt action, bull barrel, great scope, spotting scope with spotter, lots of ammo in different designs, 4 wheeler so you don’t have to walk so much, a lunch and drinks and lots of time and money. Make sure the caliber of the gun can handle the bullet required for those shots. Good luck.

  2. This is what we have come to? Who wants to study bullets for a lifetime? What are we preparing for here? For the typical 5-20 yard personal protection shot, try practicing instead of studying….the shots will help to keep you awake.

  3. I want to shoot 1000 yards. Wait! I have shot 1000 yards and it is no easy task. The guys that make it look easy are well practiced in it. It does take something beter than your average hunting rifle and factory hunting ammo to shoot these ranges consistently. Even when you have the good equipment, that darn wind is hard to master.

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