How does altitude affect .308 bullet performance?

Effects of Altitude on Bullet Trajectory

Altitude affects the trajectory of a .308 bullet due to changes in atmospheric pressure and temperature. At higher elevations, the air pressure is lower, reducing the drag on the bullet and allowing it to travel farther before dropping. However, the reduced air pressure also decreases the bullet’s velocity, which can affect its accuracy and penetration. For example, at an elevation of 10,000 feet, a .308 bullet may lose around 200-300 feet per second (fps) of velocity compared to sea level.

Compensating for Altitude in .308 Cartridges

To compensate for the effects of altitude on .308 bullet performance, shooters can adjust their aiming points. A general rule of thumb is to adjust the aiming point 1-2 MOA (minutes of angle) for every 1,000 feet of elevation gain. For example, at an elevation of 10,000 feet, a shooter may need to aim 10-20 MOA higher than at sea level to compensate for the increased drop. Additionally, shooters may need to adjust their bullet selection to choose a heavier bullet that holds its velocity better at high elevations.

Practical Considerations for Hunting at High Elevations

When hunting at high elevations, shooters should consider the specific conditions and the type of game they are hunting. For example, when hunting deer at high elevations, a heavier bullet with a higher ballistic coefficient may be more effective due to the reduced air resistance. Conversely, when hunting varmints such as prairie dogs, a lighter bullet with a higher velocity may be more effective due to its ability to penetrate quickly and deeply.