Understanding Energy Measurement in the Air Force – Joule and m/s Explained

When talking about airguns, you often hear terms like m/s (meters per second) and Joules . These measurements describe the weapon's performance and impact power, but what do they really mean? How do they affect your choice of airgun, and how are they measured correctly? In this guide, we'll go over everything you need to know about energy measurement in airguns.

What do m/s and Joule mean?

m/s – Speed ​​of the hail

m/s (meters per second) indicates how fast a shot leaves the barrel of an airgun. The higher the m/s, the faster the shot travels towards the target.

Example:

• An air rifle with 4.5 mm shot fired at 200 m/s will have a lower energy than a 5.5 mm shot at the same speed , as the weight of the shot plays a large role in the total energy.

In many other countries FPS (Feet Per Second) is used as a unit of measurement, but in Denmark it is m/s that is used. The conversion is: 1FPS=0.3048 m/s

Example: 400 FPS = 121.9 m/s

Joule – The Air Force's Strike Power

Joules measure the kinetic energy of the shot, which is a more accurate indicator of the weapon's impact force than m/s alone. Joules take into account both velocity and weight, making them the best measure of weapon performance.

• The formula for Joule:

  Joule = (Masse (kg) × Hastighed (m/s)^2) / 2

  Examples:

  • A 4.5 mm shot of 0.50 grams (0.00050 kg) fired at 250 m/s has an energy of: Joule = (0.00050 × 250^2) / 2 = 15.6 J

  • A 5.5 mm shot of 1.00 grams (0.00100 kg) fired at 200 m/s has an energy of: Joule = (0.00100 × 200^2) / 2 = 20 J

  This shows that a slower but heavier hailstone can have a higher energy than a light hailstone with high m/s.

Why is Joule important in air force?

1. Legislation:

   • In Denmark, there is no general Joule limit for air weapons .

   • However, air weapons over 4.5 mm require a weapons permit .

2. Security:

   • A high Joule airgun can penetrate paper, plastics, and even wood depending on shot weight and velocity.

   • Always wear protective equipment when using high-powered air weapons.

3. Precision and range:

   • A hailstone with higher energy maintains its speed longer and is less affected by wind.

   • However, too much force can negatively affect accuracy, especially with shots that are too light.

How do you measure m/s and Joule?

How to measure m/s with a chronograph:

1. Place the chronograph in front of the barrel so it can register the shot.

2. Shoot a shot through the meter and note the m/s value.

3. Use the weight of your shot and enter the values ​​into the Joule formula.

4. Adjust your weapon or shotgun selection depending on the results.

Example:

• A measurement shows that your air rifle shoots 200 m/s with a 4.5 mm shot of 0.50 grams .

• Calculation of Joules:
  Joule = (0.00050 × 200^2) / 2 = 10 J

• If you want to increase the energy, you can use a heavier shot or optimize the weapon's air pressure.

How do different factors affect Joule and m/s?

• Lighter hail gives higher m/s but lower energy.

• Heavier hail has lower m/s but higher energy and better stability.

2. The mechanism of the weapon

• PCP (Pre-Charged Pneumatic): High m/s and consistent performance.

• Spring-operated: Can vary in speed depending on the strength of the spring.

• Gas cylinder (IGT/Nitro Piston): Stable shots without recoil, but lower m/s than PCP.

3. Barrel design and length

• A longer run gives the hailstone more time to accelerate and increases m/s.

• However, a barrel that is too long can reduce efficiency if the pressure drops before the shot leaves the barrel.

How do you optimize your airgun based on m/s and Joule?

1. Choose the right combination of shot weight and weapon strength.

   • For precision shooting: Use heavier shot with higher Joule.

   • For fast shots: Use lighter shot for a flatter trajectory.

2. Use a chronograph to fine-tune your weapon.

   • Test different hail and note the difference in m/s and Joule.

   • Adjust the pressure in PCP guns to optimize the shooting power.

3. Adjust your aim to your bullet trajectory.

   • Use an adjustable scope if you have high Joule and a more curved trajectory

Conclusion

m/s and Joules are crucial measurements for understanding the performance of an airgun. While m/s tells you how fast a shot is moving, Joules give you a full understanding of the impact force of the shot.

To get the most out of your air force, you should:

• Use a chronograph to measure the speed of your shots.

• Experiment with different shot types and weights .

• Comply with the legislation , especially regarding caliber restrictions above 4.5 mm.

By combining m/s, Joule and shot weight correctly, you can optimize precision, range and shot power for your shooting.