My co2 sidearm is 460 fps with a .20 gram bb, so what gram bbs should i use for it?
The fps is too high for a .20 gram BB. I suggest you use a heavier and higher quality BB so it will lower the FPS. Keep in mind that the heavier the BB, the more accurate but you are going to lose some distance. I suggest you use either a .23 gram, .25 gram, .28 gram, or .30 gram.
Here are the links to those BB