Originally Posted by Styrak
Chrono with 0.20's, same as AEG's.
But yes GBB's have a different effect when moving up in BB weight.
They retain more velocity and increase in energy slightly because of the gas expansion and having more time in the barrel to use that pressure.
Fixed that for you to reduce confusion.
It's all due to the compressed gases expanding. heavier bb = more time in barrel (initially slower) for the gas to expand and fully release it's energy.
But yes, most fields measure it the exact same way as AEGs, though some host may do a joule calculation if they take the expansion effect on heavier bbs into account. Though I doubt, at least for M4 or shorter length barrels, it will have too drastic an effect, may be wrong on that though.