How does altitude affect .45-70 performance in the field?

Altitude and Ballistic Performance

When hunting at high elevations, the decreased air pressure and reduced oxygen levels can significantly impact .45-70 performance. At 7,000 feet, for example, the air pressure is approximately 75% of sea level, resulting in a 15-20% decrease in bullet velocity. This reduction in velocity can affect the expansion and penetration of the bullet, particularly in larger game like elk. To mitigate these effects, hunters may need to adjust their shot placement and trajectory compensation to ensure a clean and humane kill.

Compensating for Altitude with Trajectory Adjustment

To compensate for the effects of altitude on .45-70 performance, hunters can use a ballistic calculator or consult a trajectory chart to determine the necessary adjustments for their specific rifle and ammunition at high elevations. As a general rule, for every 1,000 feet of elevation gain, a 3-5% increase in bullet drop can be expected. For example, at 9,000 feet, a 100-yard shot may result in a 3-5 yard bullet drop. Hunters should also consider the expansion characteristics of their ammunition at high elevations, as some bullets may not expand as effectively in lower-pressure environments.

Choosing the Right Ammunition for High-Elevation Hunting

When hunting at high elevations, it’s essential to choose ammunition that is specifically designed for high-velocity applications. Look for bullets with a high ballistic coefficient (BC) and a controlled-expansion design, such as those from Hornady or Nosler. These bullets are designed to maintain their velocity and expand effectively at high elevations, even in lower-pressure environments. Additionally, consider using a heavier bullet weight (e.g., 325-350 grains) to achieve deeper penetration and ensure a clean kill in larger game like elk.