Seeing as you guys are unwilling to let it go and seem intent on trying to dirty The Siege Projects good name, here’s a little education tool. I use this to explain why my and many other sites restrict HPA and GBB on site. Contrary to conspiracy theories all we’re trying to do is protect YOU the end user, so without further a-due please read on.
What is the Difference Between Joules & FPS
While both joules and FPS can give an indication of your gun’s power, they are measuring different things. FPS is a measure of velocity, changing relative to the weight of a BB – heavier BBs mean less FPS, but this has no bearing on joules.
So, although the FPS of your gun may change depending on the weight of your BB, the level of kinetic energy (joules) it produces should always remain the same – in theory.
What is Joule Creep?
We say ‘in theory’ because there is something known as ‘joule creep’, which refers to how much air is present to push the BB out of the barrel.
The perfect amount of air in the system ensures your BB leaves the barrel with the right amount of joules and energy. Too little air means your BB stops accelerating before it reaches the end of the barrel, losing potential energy. Too much air means your BB will leave the barrel with the proper joule rating, but you will have excess air in the barrel that gets wasted, potentially destabilising the BB and leading to less accuracy.
Although many AEGs experience minimal joule creep, HPAs and GBBRs can see it happen more commonly.
You can counteract excess air by using heavier BBs. This being said, doing so is often against site rules, as when you chrono at the start, you should be doing so with the system setup you intend to use.
To find out more about using a chronograph to test how powerful your gun is, see our guide, which especially helpful for airsoft newbies.
What is airsoft chronograph?
It is worth noting that it is possible to fire over the limit without intending to. Again, unlikely for AEG users, but it can be seen for HPA and GBBR players. Changes in the temperature can easily affect the gun’s output, often without the player even realising it.