You should only really be using .25s or maybe .28s
FPS is usually measured with .20s, and stock G&Gs tend to be 360ish.
The reason that your wieght of BB's isnt particularily important when measuring FPS is that regardless of the wieght, your shots will always have the same amount of energy, measured in joules.
So, 360 FPS with .20s is about 1.20 Joules.
Convert that to 0.25 puts you at about 320 FPS
Most new players think that a low FPS is bad, therefore they stay away from heavy wieghts, but you will see much better accuracy and brush penatration with .25s or .28s
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