Is 147 Grain 9mm Subsonic? Understanding Ammunition and Sound Suppression
The simple answer is: a 147 grain 9mm bullet can be subsonic, but it's not guaranteed. Whether or not a specific 147 grain 9mm round is subsonic depends entirely on the powder load and the bullet's design.
Let's break down why:
What makes a bullet subsonic?
A bullet's velocity is the key factor. Subsonic means the bullet is traveling slower than the speed of sound. The speed of sound varies slightly depending on temperature and altitude, but it's generally accepted to be around 1125 feet per second (fps) at sea level. Therefore, any bullet traveling slower than 1125 fps is considered subsonic.
Why 147 grain is often associated with subsonic ammo:
Heavier bullets, like the 147 grain 9mm, generally require less powder to achieve a given velocity. This slower velocity is advantageous for subsonic ammunition. Manufacturers often utilize heavier bullets in conjunction with specific powder charges designed to keep the velocity below the speed of sound. This is crucial for suppressors, as supersonic rounds create a significant sonic crack, negating the sound suppression effect of the silencer.
Factors Influencing Subsonic Velocity:
- Powder Load: The amount of propellant used is the most significant factor. Less powder equals lower velocity.
- Bullet Design: The shape and construction of the bullet can impact its ballistic coefficient (BC). A higher BC means the bullet is more aerodynamic and will retain velocity better over distance. However, even with a high BC, insufficient powder will still result in a subsonic velocity.
- Barrel Length: A longer barrel allows for more complete powder burn, potentially leading to higher velocity. Shorter barrels can help ensure subsonic speeds, even with slightly larger powder charges.
- Manufacturer: Different manufacturers have different loading specifications, and even seemingly identical rounds from different manufacturers can have slightly different velocities.
How to Know if Your 147 Grain 9mm is Subsonic:
The only reliable way to determine if your specific 147 grain 9mm ammunition is subsonic is to check the manufacturer's specifications. This information is usually printed on the box or available on the manufacturer's website. Look for velocity data measured in feet per second (fps) or meters per second (m/s). If the velocity is below 1125 fps, then it is subsonic.
In Conclusion:
While a 147 grain bullet often indicates subsonic ammunition in 9mm, it's not a guarantee. Always verify the velocity on the manufacturer's packaging or website to confirm whether the round is truly subsonic. Don't rely on assumptions; always check the specifications to ensure you're using the appropriate ammunition for your needs.
