Originally Posted by L473ncy
Since pretty much every BB has an "air bubble" in them you also want to make sure that it's in the "centre" or close to the centre. It would make sense that a BB with an air bubble that's off to the side or something when it passes through the hop up and down the barrel will have a weird flight path since the weight isn't totally distributed evenly. Simple high school physics.
Not sure if the above made sense but in a nutshell you want your BB to have as small of an "air bubble" in it as possible and preferably have it in the dead centre.
I thought that a while before as well, but after cracking various brands open, that doesn't seem to be the case with a lot of them. I would guess that it's more density of materials than a lack of it.