The question of how far a .308 Winchester (7.62x51mm NATO) round will shoot "flat" is complex and doesn't have a single definitive answer. The term "flat" is subjective and depends heavily on the shooter's definition of acceptable bullet drop. What one shooter considers "flat" another might find unacceptable. Several factors significantly influence bullet trajectory and effective range:
Factors Affecting .308 Flatness and Range
Several key factors interact to determine how far a .308 bullet remains relatively flat:
1. Ammunition:
- Bullet Weight: Heavier bullets generally have a flatter trajectory than lighter ones at the same velocity, due to their higher momentum. A 175-grain bullet will have a flatter trajectory than a 150-grain bullet, all other things being equal.
- Bullet Design: The ballistic coefficient (BC) of a bullet is a crucial factor. A higher BC indicates a more aerodynamic bullet, experiencing less air resistance and thus maintaining velocity and a flatter trajectory over longer distances. Match-grade ammunition with boat-tail bullets typically boasts a higher BC.
- Powder Charge: The amount of propellant significantly impacts muzzle velocity. Higher velocity generally translates to a flatter trajectory, although excessive velocity can lead to instability at longer ranges.
2. Rifle and Optics:
- Rifle Twist Rate: The rate of rifling in the barrel influences bullet stability. A faster twist rate can stabilize heavier bullets, allowing for longer-range accuracy.
- Muzzle Velocity: The initial speed of the bullet exiting the barrel directly impacts its trajectory. A higher muzzle velocity contributes to a flatter trajectory, but again, excessive velocity may lead to instability.
- Scope Zeroing: The distance at which the rifle scope is zeroed (typically 100 or 200 yards) influences how the bullet drops at longer ranges. Proper zeroing is critical for accuracy at extended distances.
3. Environmental Conditions:
- Wind: Wind is perhaps the biggest factor influencing bullet trajectory at longer ranges. Crosswinds will significantly deflect the bullet, while headwinds and tailwinds will affect the bullet's velocity and trajectory.
- Temperature: Temperature affects air density, which in turn impacts bullet drag. Colder air is denser, resulting in increased drag and a steeper trajectory.
- Altitude: Altitude affects air density similar to temperature; higher altitude means thinner air and less drag, leading to a flatter trajectory (until extreme altitudes where the air thins considerably).
Defining "Flat" and Practical Considerations
Many shooters consider a bullet trajectory to be "flat" if the bullet drop is within a few inches at ranges out to 300-400 yards. Beyond this distance, bullet drop becomes increasingly significant, requiring considerable holdover or adjustments. While some high-BC, heavy-grain .308 loads might maintain a relatively flat trajectory out to 600-800 yards, it's crucial to understand that this is highly dependent on all the aforementioned factors and requires expert-level marksmanship and environmental considerations.
It's highly recommended to engage in practical shooting at various ranges to understand how your specific .308 setup performs. Using a ballistic calculator and considering environmental conditions during your practice sessions are crucial for accurate long-range shooting.
Conclusion
There's no single answer to how far a .308 shoots flat. The effective range where the trajectory remains sufficiently flat for practical purposes depends on ammunition, rifle, optics, and environmental conditions. Understanding these factors and using appropriate tools and techniques is critical for achieving accuracy at any distance. Prioritize safety and responsible firearms handling practices at all times.
