We use .20g exclusively indoor since guns are chronoed every game to make sure they're within field limits. That and we're to lazy to do the math to figure out what a gun is shooting if someone is using a different weight BB... Our indoor arena has no areas where using a heavier BB will improve your accuracy either, shooting distances are between 5ft and 12ft almost everywhere with the exception of some of the longer halls.

We also don't allow full auto during indoor, so shots are almost always placed accurately.