The non-drive side cup (assuming we're talking about a cartridge type bb here) has a wedge shape to it and will only go in so far. Forcing it in further will either pinch the bearings or crack the cup.
This is Africa, 1943. War spits out its violence overhead and the sandy graveyard swallows it up. Her name is King Nine, B-25, medium bomber, Twelfth Air Force. On a hot, still morning she took off from Tunisia to bomb the southern tip of Italy. An errant piece of flak tore a hole in a wing tank and, like a wounded bird, this is where she landed, not to return on this day, or any other day.