Hitting Your Mark with the .308: Mastering the 100-Yard Zero with 168-Grain Bullets

Understanding How a Bullet Flies

Before we get into the specifics of the .308 and the 168-grain bullet, let’s lay a foundation by discussing the fundamental principles that govern a bullet’s path through the air. The study of a bullet’s flight is called ballistics, broadly categorized into several stages.

Internal Ballistics

This encompasses what happens *inside* the firearm from the moment the trigger is pulled to the moment the bullet exits the muzzle. It’s about the ignition of the primer, the rapid expansion of propellant gases, and the acceleration of the bullet down the barrel.

External Ballistics

This is the stage we’re most concerned with. External ballistics examines the bullet’s trajectory after it leaves the muzzle, focusing on factors that influence its path. These include gravity, air resistance, wind, and the bullet’s ballistic coefficient.

Terminal Ballistics

This phase deals with what happens when the bullet *hits* the target. It’s about the bullet’s impact, the transfer of energy, and the resulting effects on the target, be it a game animal or a paper target.

Several key terms are fundamental to comprehending external ballistics:

Muzzle Velocity

This is the speed at which the bullet leaves the barrel, measured in feet per second (fps) or meters per second (m/s). It’s a primary factor in determining the bullet’s trajectory and range.

Ballistic Coefficient

This numerical value quantifies a bullet’s ability to overcome air resistance. A higher ballistic coefficient (BC) means the bullet is more aerodynamic and resists air drag more effectively. This typically translates to less drop and less wind drift over long distances.

Bullet Drop

Gravity relentlessly pulls on all objects, including bullets. Bullet drop refers to the vertical distance a bullet falls over a given distance. This drop necessitates aiming slightly above the target to compensate.

Wind Drift

Wind is another major factor. It pushes the bullet sideways, causing it to drift off course. The amount of wind drift depends on the wind speed, the angle of the wind, and the bullet’s BC.

Energy

As a bullet travels, it possesses kinetic energy, which is a measure of its ability to do work. Energy is typically measured in foot-pounds (ft-lbs) or Joules. The energy of a bullet is highest at the muzzle and decreases as the bullet slows down.

The .308 with the 168-Grain Advantage

Why is the 168-grain bullet so popular in the .308 Winchester? The answer lies in its versatility and balanced performance characteristics. It sits in a sweet spot where the advantages of power, accuracy, and manageable recoil come together.

Accuracy

The 168-grain bullet is often favored by target shooters because of its inherent accuracy. Many rifles are designed, and barrels are rifled, to optimize their performance with bullets of this weight.

Effective Range

While the .308 Winchester can be effective at longer ranges, the 168-grain bullet offers an optimal blend of trajectory and retained energy for many hunting and target shooting scenarios. It carries enough energy to deliver ethical kills on medium-sized game while also maintaining acceptable downrange ballistics for competitive shooting at various distances.

Recoil

Compared to heavier bullets, the 168-grain bullet produces less recoil, making it more comfortable to shoot. Reduced recoil allows for quicker follow-up shots and generally improves shooting accuracy.

Beyond the general benefits, it’s important to recognize that the specific characteristics of a 168-grain bullet will vary based on the manufacturer, bullet design, and the propellant load. The ballistic coefficient, muzzle velocity, and downrange performance will be slightly different for each load. Therefore, you must consult load data for the *specific* ammunition you are using.

Putting it on Paper: The Ballistics Chart

To effectively utilize a .308 rifle with a 168-grain bullet, you must understand its trajectory. The most useful tool for this is a ballistics chart. This provides a concise, yet accurate representation of how a bullet travels. Because every rifle and load will perform slightly differently, this chart is a generalized guideline. However, it provides a starting point for learning and can be adjusted as you experiment and refine your understanding.

*Important Note: The following chart provides data that is representative for a popular 168-grain bullet, but the data will vary with each individual firearm, ammunition, and atmospheric conditions.*

The numbers below assume a bullet with a Ballistic Coefficient (BC) of .462, and a muzzle velocity of 2700 fps. Other factors are a zero at 100 yards, and standard sea level conditions (59°F / 15°C, 29.92 inHg atmospheric pressure). This data is for illustrative purposes only. ALWAYS consult the manufacturer of your chosen ammunition, or a qualified ballistics calculator, for specific load data.

Using the Chart: A Practical Guide

Let’s look at how to use this chart. If you are shooting at 300 yards, you would expect your bullet to drop approximately 30.8 inches below your point of aim. Furthermore, if there’s a crosswind of 10 mph, you’ll see approximately 33.5 inches of drift.

From Theory to Practice: Zeroing at 100 Yards

A *zero* is the process of adjusting your rifle’s sights (scope or iron sights) so that the bullet impacts the target at a specific range, usually the range at which you plan on using the rifle. Zeroing at 100 yards is a practical starting point for the .308 with a 168-grain bullet. This gives you a good balance of accuracy and allows for easy adjustment for longer-range shots.

Here’s how to achieve a 100-yard zero:

Gather Your Equipment

You’ll need your rifle, your scope (if applicable), ammunition (the 168-grain .308 load you intend to use), a stable shooting platform (a bench, shooting bag, or tripod), a target (preferably with grid lines), and a way to measure distances accurately (a rangefinder is best, but a tape measure will work if needed).

Ensure Safe Practices

Always, *always*, follow safe gun-handling rules. Verify the firearm is unloaded and pointed in a safe direction. Wear eye and ear protection. Only load the rifle when you’re ready to shoot, and always treat every firearm as if it’s loaded.

Prepare Your Rifle

Before even firing a shot, get your scope on your rifle. If you have a new scope, you will have to mount it and get it as square with the receiver as possible.

Bore Sighting

Before you start shooting, use bore sighting. This can be done by removing the bolt from the rifle and looking through the bore (the barrel) to see the target. This helps you align the bore with the target.

Initial Shots and Adjustments

Now, set up your target at 100 yards. Take a few carefully aimed shots. The first few shots will likely be off target. Look at the target and note where your shots are hitting relative to your point of aim. Use your scope’s adjustments (turrets) to move your point of impact to the center of the target.

Most scopes have markings on their turrets that indicate the amount of adjustment per click. (e.g., ¼ MOA (minute of angle) or 1/8 MOA). A ¼ MOA adjustment will move your bullet impact approximately ¼ inch at 100 yards. Make the necessary adjustments to your scope to move your point of impact to the center of the target. If your shots are high and left, you will adjust your scope down and right, and vice versa.

Fine-Tuning

After making adjustments, fire another group of shots. Evaluate where your shots are impacting. Make further, more precise adjustments until your group of shots centers on your point of aim.

Understanding the Other Variables

While a 100-yard zero is a great foundation, several factors will influence your bullet’s trajectory beyond that range.

Wind

Wind is a significant influence on bullet flight. The stronger the wind, and the longer the distance to the target, the more the wind will affect your bullet’s path. Reading wind requires practice, experience, and an understanding of how wind affects your chosen load. Learning to estimate wind speed, wind direction, and applying these estimations to your shots is crucial for long-range accuracy. The chart provided above gives you some idea of the wind drift, but this will change based on the actual wind speed.

Altitude and Air Density

Altitude also affects ballistics. At higher altitudes, the air is less dense, which reduces air resistance and can result in a flatter trajectory and less wind drift. Temperature also plays a part in air density, and thus, ballistics. You can compensate for these variables through the use of ballistics calculators, which allow you to input environmental conditions.

Other Environmental Effects

Humidity can influence the ballistics, but its effect is usually minimal unless you are shooting at extreme distances or in very humid conditions.

Extending the Range

Using your 100-yard zero and a ballistics chart, you can extend the effective range of your rifle. You can use the chart to determine how much to “hold over” or aim above your target, at different distances, to compensate for bullet drop. Some shooters also use scope reticle markings (like mil-dots or MOA hash marks) to aid in holdover. A rangefinder and a good understanding of windage adjustments become indispensable at longer distances.

Choosing the Right Load

The 168-grain bullet is a versatile choice, but you will find it in various configurations.

Match Bullets

These are designed for maximum accuracy and are generally used in target shooting.

Hunting Bullets

These are designed to expand on impact, creating a larger wound channel and maximizing terminal performance.

Choosing the right bullet depends on the application. If your primary focus is target shooting, a match bullet will probably serve your needs best. If you’re planning on hunting, select a hunting bullet designed for the game you are pursuing. Always do your homework and choose the right tool for the job.

Wrapping Up

Understanding the fundamentals of ballistics is key to success with any firearm. The .308 Winchester, loaded with a 168-grain bullet, offers a great blend of power and accuracy. A 100-yard zero provides an effective foundation. By understanding the ballistics, using a ballistics chart, and practicing consistently, you’ll be well on your way to achieving consistent hits on your targets, at ranges out to several hundred yards and even beyond.

Always remember that responsible firearm ownership requires a commitment to safety and ongoing education. Continued practice and the willingness to learn are essential for any marksman.