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Hi. Me and my friend made an experiment with this airsoft gun

We had three different BB weights to try out - 0.12 gram, 0.20 gram and 0.32 gram. We measured the velocity in m/s with a chronograph.

The chronograph shows also the muzzle energy but a simple calculation using the weight and the velocity provided exactly the same value as the one shown on the chronograph.

We fired 10 shots with each BB weight and made and MS Excel table.
To my surprise the heavier the pellet the higher the muzzle energy delivered. Consistently. 0.12 gram pellet delivered as high as 0.6 joules. 0.2 gram pellet delivered as high as 0.73 joules. 0.32 pellet delivered as high as 1 joules!

Why is the gun able to deliver higher energies with heavier pellets? Initially, I thought that the capacity of the gun to deliver a given amount of joules to the BB is fixed and should not depend on the pellet mass.

For a heavier bullet, the velocities are lower of course. But apparently not low enough to compensate for the higher mass in the formula. In the end, the heavier BB moves slower, but still fast enough to deliver higher energy than a lighter BB.

Please someone try to explain this in details to me. It's troubling me awfully. The Excel table with measured velocities is attached. Thanks a million in advance.
 

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It's called Joule Creep and it's nothing new :)
It's the main reason why fields shouldn't chrono guns on 0.2s only and FPS-m/s, but use Joules with the "game" bb weight.

Basically what happens is that with higher mass, the "energy source" (compressed air or green gas/co2) has more time to transfer energy to the pellet since it takes longer for it to leave the barrel compared to a lighter bb.

Don't know the exact physical property or name of this process though.
 

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As mentioned above, it’s “scientifically” called joule creep. It’s interesting, but kind of just how it is. You use a heavier bb, you have more joules. Joule creep has become something more deliberate and substantial. Such as .20 vs .48. Making the outputs have a larger difference in joules and smaller difference in fps. For example, and ideal joule creep build would shoot around 500fps with a .20 and preferably 400+ fps with a .48. Which makes the .48 joule output spicy.

But why/how are the heavy bb fps numbers LOWER, but the joule numbers HIGHER? You could just say “that’s physics” but what helped me understand it more is this;

You are going to be hit by an object going 30 mph. Would you prefer that object to be a tennis ball or a car? Lol, well, the car, weighing way more, will hurt a LOT more. That’s because it’s heavier, with more energy. That’s joules for the bb. Stick to the tennis ball hehe.
 

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Discussion Starter #4
Many thanks to both of you. This is what I was looking for.

Tennis ball versus car hitting me. If the car is moving at a speed of 1 meter per hour and the ball is moving at 1000 kilometer per hour I would prefer the car hitting me. :yup:
 

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So what you want to do is, build a car that has the same energy as a tennis ball at 30mph. Then you can have your friend drive directly at you, but you could stop the car with your bare hands. SCIENCE.
 

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To add some math/physics into this

Force = Mass * Acceleration <- This is Newton’s second law of motion

What the previous posters are talking about with joule creep, is Force, it is a measure of energy

Force is dependent on the mass and velocity , you had correctly eluded to it with your tennis ball and car example

Final Velocity = Initial Velocity + (Acceleration * Time)

Since the initial velocity is zero, final velocity is acceleration * time. The longer the bb is in the barrel the more time it has to accelerate and gain energy. The bb is in the barrel longer based on the application of Newton’s first law of motion - An object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force. Basically it is saying that it is 'harder' for a heavier bb to accelerate (because it resist the new force) and therefore takes more time to accelerate. More time to gain energy...higher joule rating
 

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As mentioned above, it's "scientifically" called joule creep. It's interesting, but kind of just how it is. You use a heavier bb, you have more joules. Joule creep has become something more deliberate and substantial. Such as .20 vs .48. Making the outputs have a larger difference in joules and smaller difference in fps. For example, and ideal joule creep build would shoot around 500fps with a .20 and preferably 400+ fps with a .48. Which makes the .48 joule output spicy.

But why/how are the heavy bb fps numbers LOWER, but the joule numbers HIGHER? You could just say "that's physics" but what helped me understand it more is this;

You are going to be hit by an object going 30 mph. Would you prefer that object to be a tennis ball or a car? Lol, well, the car, weighing way more, will hurt a LOT more. That's because it's heavier, with more energy. That's joules for the bb. Stick to the tennis ball hehe.
Actually pretty basic stuff. The equation for energy is 0.5 x mass x velocity squared, or (1/2)mv^2. The units used for mass are kilograms, and m/a for velocity. .2 grams is 0.0002 kg, and 500 fps is 152.4, thus the energy output is 0.5 x 0.0002 x 152.4^2 = 2.32 joules. For a 400 fps .48 projectile, the same equation is 0.5 x 0.00048 x 121.9^2 = that spicy 3.57 joules.

Velocity does play a major role, as the only variable being squared, but if you drop the velocity by only 100 fps, but more than double the mass, you're going to have some pretty high energy outputs.
 

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The BB is in the barrel longer if it is slower, so it will use more often gas/air from the gun than a lighter BB going faster.

This is called Joule Creep and it is quite well known, so well known that CQB players will try to boost the power of their gun by using really heavy BBs and they usually end up hurting someone.
 
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