Elite Force bbs are well known in the airsoft community. Unfortunately, we do not know which manufacturer Elite Force uses for these bbs, however, we do know it is not BLS.
Elite Force BBs
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Here is a chart of recommended BB weights for Fps measured with .2g
~320 FPS .2g
320-360 FPS .25g
360-400 FPS .28g
400-450 FPS .32g
450-500 FPS .36g
These are recommended weights for fully automatic guns. The fps sometimes overlapps, when it does, you can use either bb weight for good performance. This chart does not necessarily apply to sniper rifles, you can find their chart on heavy weight BB pages.