The soda can is often called as the "poor man's chrono" for those who want to check their power of their airsoft guns though measurement is in terms of FPS. How do you do it with joules? Will it be the same thing? Watch Joe Toys show how it is done... "If there is no tachometer, how can we know how many joules are in our air gun? This time I will teach you how to use a soda can to know the approximate joules of your toy gun. Note! Although you need real data, it is more accurate to buy a speed tester. You can buy Pepsi or Coca-Cola as you like."