Speed Vs Power

Its one of the most common misconceptions around in the casual air gun shooter world. If I had a penny for every time I heard someone tell me there gun shoots 1000fps I would have more money then I know what to do with. The reality is that most air gun manufacturers will mislead the ill informed public into believing that their product is better than it really is. The idea that speed equals power is simply false and hopefully by the end of this article you will know why.

The Science of It

Lets start with a little science, the kinetic energy of an object in motion is calculated by its mass multiplied by its velocity, we use the constant “450240” in shooting to work out the energy of a projectile as it leaves the barrel or indeed at any point in its trajectory.

The formula for FPE (foot pounds of energy) is:

m.v2/450240

m= mass of projectile

v= velocity it travels

So if we take an 8.4gr (grain) pellet moving at 800fps (feet per second) we can work out its energy like this.

8.4x(800×800)=5376000

5376000/450240=11.94fpe

The Reality

Lets face it 11.94 of anything sounds a whole lot less then 1000 of something else!

1000 fps sounds like a great deal of speed but what exactly is going that fast? Is it a brick traveling at 1000 fps? Is it a cotton ball going 1000 fps?

Id be petrified of the brick but would gladly stand in front of the cotton ball for a beer. So let’s take a look at the reality of this advertising gimmick. We will use the same gun to work out what exactly it can shoot at 1000 fps

 

Remember (m.v2/450240)

So:

m.(1000.1000)/450240=11.94 fpe

m.1000000/450240=11.94 fpe

m=(1000000/450240)/11.94 fpe

m= 5.37

From that we can see that to attain a velocity of 1000fps a 5.37gr projectile would need to be used. Given that the average pellet in .177cal weighs between 8-10gr, 5.37gr would be a very light pellet.

Now you may ask yourself “what’s to stop me from using a very light pellet to get super speed?”  The answer is not all that cut and dried as there are a few points to consider.

First off if you are using a spring powered rifle you will most certainly do serious damage to the internal working parts of the gun as there will be considerably less resistance to stop the piston slamming into the front of the cylinder at the end of its stroke. This will put excessive strain on your main spring as well as ruin your piston seal.

So hyper velocity pellets will wreck your gun? What about accuracy? The un resisted piston will cause more problems when it comes to accuracy, all that wasted energy will be transferred to the rifle stock and then to the shooter in a huge amount of perceived recoil, thus creating more vibrations within the gun before the pellet has left the barrel throwing it off target. The next issue with super sonic pellets is just that…they go super sonic and break the sound barrier, being an ultra light pellet it will not be able to resist the additional forces at play and will start to tumble!

So super sonic pellets can never be accurate and when you really get down to it, if you miss then it doesn’t matter what you shot with.