What Is a Maximum Ordinate Trajectory Chart?
Before diving into specifics about the 168 grain bullet, it’s important to clarify what a maximum ordinate trajectory chart is. Simply put, this chart maps the bullet’s trajectory above the line of sight at various ranges. The "maximum ordinate" represents the highest point the bullet reaches relative to the shooter's line of sight during its flight to the target. Usually, when a bullet is fired, it doesn’t travel in a straight line. Instead, it follows a curved path due to gravity and air resistance. Shooters zero their rifles at a certain distance, but the bullet often rises above the line of sight before dropping back down to hit the target. The maximum ordinate tells you the peak height of that arc, which is crucial for understanding bullet drop and wind drift.Why Focus on the 168 Grain Bullet?
The 168 grain bullet is popular among precision shooters, especially in cartridges like the .308 Winchester and 6.5 Creedmoor. Its heavier weight compared to lighter bullets (like 150 or 155 grains) offers better momentum and stability, which translates to improved accuracy at longer distances. The balance between velocity and weight allows the 168 grain bullet to maintain supersonic speeds longer, reducing the effects of wind and gravity. If you’re hunting medium to large game, or competing in long-range precision shooting, knowing the trajectory for a 168 grain bullet helps you make more informed decisions about holdover, elevation adjustments, and even ammunition selection.Key Ballistic Factors Affecting the 168 Grain Trajectory
- **Muzzle Velocity:** The speed at which the bullet leaves the barrel profoundly impacts its trajectory. Higher velocities flatten the curve, reducing the maximum ordinate.
- **Ballistic Coefficient (BC):** This number measures the bullet’s ability to overcome air resistance. A higher BC means a more streamlined bullet that retains velocity better.
- **Zero Range:** The distance at which the rifle sight is zeroed affects the height and shape of the trajectory arc.
- **Environmental Conditions:** Wind, temperature, humidity, and altitude also influence the bullet’s flight path.
Reading and Using a Maximum Ordinate Trajectory Chart for 168 Grain Bullets
If you have access to a maximum ordinate trajectory chart for a 168 grain bullet, here’s how you can make the most of it.Understanding the Chart Layout
Typically, the chart will plot distance along the horizontal axis (measured in yards or meters) and height above the line of sight on the vertical axis (usually in inches or centimeters). The highest point on the curve represents the maximum ordinate. For example, if your rifle is zeroed at 200 yards, the chart might show that the bullet rises 3.5 inches above the line of sight at around 100 yards before dropping back down to zero at 200 yards.Practical Applications
- **Range Estimation:** By knowing where the bullet reaches its apex, you can better estimate holdover when shooting at varying distances.
- **Scope Adjustments:** If you’re shooting targets at multiple ranges, understanding the trajectory helps you dial elevation and windage settings more accurately.
- **Avoiding Obstacles:** Hunters often need to clear brush or other obstacles. Knowing the maximum ordinate helps in judging whether the bullet will clear these obstacles without hitting them.
Comparing 168 Grain Trajectory to Other Bullet Weights
- **Lighter Bullets (e.g., 150 grain):** These tend to have a flatter trajectory due to higher initial velocity but can be more affected by wind drift.
- **Heavier Bullets (e.g., 175 grain):** Heavier bullets can maintain energy better at long distances but often have a more pronounced arc and higher maximum ordinate.
How Zero Distance Affects the Maximum Ordinate
The zero range you select has a big influence on the maximum ordinate. For instance, zeroing a 168 grain bullet at 100 yards will create a different trajectory arc compared to zeroing at 200 yards. Generally, a longer zero distance reduces the maximum ordinate, flattening the trajectory over typical hunting or competition ranges.Tips for Using Maximum Ordinate Trajectory Charts Effectively
- **Match Your Ammunition and Rifle:** The chart is only accurate when paired with the exact bullet, powder charge, barrel length, and rifle you’re using.
- **Use Ballistic Calculators:** Modern ballistic software can generate maximum ordinate charts based on your specific load and environmental conditions.
- **Practice at Multiple Distances:** Don’t just rely on the chart—shoot at varying ranges to verify and internalize how your 168 grain bullet performs.
- **Account for Environmental Changes:** Always adjust for wind, temperature, and altitude, as these factors can shift the bullet’s path, especially at longer distances.