The .308 Winchester (or 308 Win) is one of the most popular rifle cartridges for long-range rifle target practice. It is also useful for hunting game animals and competitive shooting.
However, one major challenge for long-range .308 shooters is calculating the time for a .308 round to cover 900 yards. If you face the same difficulty, this is the place for you.
Here, we’ll see various factors that affect the time it takes for a .308 round to cover 900 yards. So, let’s dive in here without wasting any time.
Understanding the Basics of .308 Winchester
Granite will always be known for its unforgiving nature, but the .308 Winchester is undoubtedly the most well-balanced rifle cartridge available abroad. Its best features are speed, efficiency, and versatility.
The bulk of the rifle cartridge is 150 – 180 grains. Higher-weight projectiles are typically favored for extended ranges as they have superior BC and performance while battling elemental forces like wind.
Primary Factors That Impact Flight Duration
The flight duration it takes 308 rounds to go 900 yards mainly depends on the following factors:
1. Muzzle Velocity
This term refers to a bullet’s speed upon discharge from the barrel. Muzzle velocity determines the bullet’s flight time. For instance, a 168-grain bullet discharged at 2,700 fps will have less flight time than a 150-grain bullet shot at 2,500 fps.
2. Weight of the Bullet and its B.C
Heavy projectiles, which also possess a high B.C. (175-grain Sierra Match King), carry more weight and are better capable of retaining velocity. This minimizes bullet drop and provides a flatter trajectory.
3. Barrel Length
A longer barrel, such as a 24-inch barrel, will provide greater muzzle velocity and reduce flight time. On the other hand, shorter barrels may result in lower speeds along with extended flight times.
4. External Conditions
These features, also referred to as the atmosphere, influence the entire condition in which the flight occurs. The density of the air, the speed of the wind, and the temperature also impact the flight. For instance, cooler, denser air enhances drag at sea level while reducing it during high altitude or warm settings.
Measuring Flight Duration for an Approximated Distance of 900 Yards
While determining how long a .308 round spends in the air traveling towards a distance of 900 yards, it is essential to note the bullet’s travel path, velocity, and environment.
Calculation Example
- Bullet: 168 grain Hornady A-MAX.
- Muzzle Velocity: 2700fps.
- Ballistic Coefficient: 0.483.
- Conditions: Sea level, no wind.
After noting the parameters, we exercise JBM Ballistics, or similar software, to determine the time of flight to the 900-yard mark. This takes about roughly 1.2 seconds when allowing for drop time, drag, etc., to be incorporated.
Choice of Bullet Impact
- Heavier Bullets: A 175-grain Berger VLD sustains flight time due to a much higher BC in comparison to the 168-grain bullet.
- Lighter Bullets: A 150-grain FMJ is observed to increase the deceleration rate and, thus, have a higher flight time due to its lower BC.
The Role of Barrel Length and Twist Rate
The barrel length and twist rate are important factors that affect both the accuracy and performance of .308 rounds at long-distance ranges.
1. Barrel Length
- A 24-inch barrel improves muzzle velocity, reducing the bullet’s flight time.
- A 20-inch short barrel will produce lower speeds and hence require a relatively longer flight time.
2. Twist Rate
Twist rate, for example, 1:10, is a factor that determines the stabilization of the bullet in the flight. The averageness of the twist gives the bullet proper flight accuracy and repeatability, especially with the heavy 208 A-MAX bullets.
Environmental Factors and Their Impact
1. Air Density
- When at sea level, colder air increases drag on the bullet, extending its flight time.
- A bullet’s flight time is shortened due to reduced air density, which allows it to travel faster at warm temperatures or higher altitudes.
2. Wind Conditions
- Crosswinds exert minimal impact on flight time but do cause lateral drift.
- Tailwinds may reduce the flight time as opposed to headwinds, which slow the bullet down and increase the flight time needed.
Practical Tips for Long-Range Shooting
1. Choosing the Right Bullet
- High-BC Bullets: For long-distance shots, use 175-grain Sierra MatchKing or 168-grain Hornady A-MAX bullets.
- Bullet Design: Match-grade bullets with aerodynamically designed heads, such as Lapua Scenar, have less drop and provide better trajectories, so they are more accurate.
2. Using a Ballistic Calculator
A JBM Ballistics is great for accounting for muzzle velocity, BC, and atmospheric conditions. It aids shooters in calculating the anticipated time of flight, bullet drop, and wind drift. Federal’s Ballistics Calculator outputs all the information needed to shoot accurately, including precision data and weather information.
3. Load Development
To determine the optimal combination for your rifle, try various loads with different bullet weights, powder charges, and primers. A suggested load is a 168-grain bullet with a velocity of 2,700 fps at 900 yards.
4. Shooting Practice
Long target practice helps a shooter notice how the rifle shoots so they can make changes or how it does not so they do not improve performance. Use F-Class or yard targets for some practice.
.308 Winchester Compared To Other Cartridges
The .308 Winchester is best for long-range shooting, but a closer look reveals that it has some minor flaws when compared to other cartridges, such as the .300 Win Mag or Creedmore.
- .300 Win Mag: This cartridge offers higher velocities and minimum drop rates at elongated distances but has more recoil.
- 6.5 Creedmoor: Very well known for its higher BC, this cartridge has a popularized flare to it primarily due to its uses stemming from long-range shooters needing a flatter trajectory.
Conclusion
From our research, we have gathered that the time it takes for a .308 round to reach 900 yards is roughly between 1.1 and 1.3 seconds. The main factors that alter the time include the weight of the bullet, muzzle velocity, and environmental conditions. For a heavier bullet with high BC, we recommend the 175-grain Sierra MatchKing, which often performs well at longer distances due to wind resistance and velocity retention. Tracker shooters are advised to use a ballistic calculator regularly, switch to high-BC bullets, and practice more often. By understanding the preceding and following details, whether one is target shooting, hunting game animals, or competing in a long-range shooting competition, one can achieve better accuracy and consistency.
