BASIC rule of thumb for buying airsoft BB's:
300-350 FPS: 0.20 G
350-400 FPS: 0.25 G
400-450 FPS: 0.28 G
450-500 FPS: 0.36 G
500 FPS: 0.43 G
BB's can be an inexpensive investment. But keep in mind that buying cheap BB's
will not only cause damage to the gearbox components , but can burn a hole in your wallet for expensive repairs in the long run.
You may ask yourself , why are they so cheap ? This is because they are intended to be used for low quality Airsoft guns. If you have the chance to buy these type of BB's , you will notice their size, shape and weight is wrong . Some of them are not even perfectly round .
Most Airsoft guns are equipped with a tight drill 6 mm barrel . Wrong size BB's will not be pushed so far because these BB's are not "tight fit" with the barrel. So air can escape the bullet , instead of catching the air behind the BB's that makes it possible to push the BB's harder out of the barrel .
To buy cheap BB's is like putting 87 octane gasoline in a car that requires 92 octane to run properly .
So do yourself and your airsoft guns one servitude , buy quality BB's. You'll thank yourself later .
Happy Airsofting !