Originally Posted by D.Kovacs
the air bubble is supposed to be there, and to be centered.
The air bubble is there because it is a byproduct of the manufacturing process. During manufacture, as the BB is formed, any air collects and concatenates towards the centre of the BB. Most of the air will collapse into a single bubble, which may or may not be formed off-centre (most will be on-centre). In higher-quality BBs, the goal is to either minimize or eliminate the air bubble.
BB Bastards (BBB) and Airsoft Central (AC) both manufacture high quality BBs. The BBBs I've cut open typically do not have an air bubble, though they do tend to have more like a "foamy" centre - which sort of distributes the "air bubble" around so that the BB is significantly less likely to be lopsided. The ACs I've cut open were solid all the way through, so the odds of them shooting lopsided is practically nil.
I'm planning to run BBB and AC comparisons for similar weights sometime in the next month. BBB will include the standard and bio rounds, AC just standard rounds. I may throw in other manufacturers also, depending on what I have laying around, again just to compare.
And if I'm feeling REALLY productive, I may post on the subject.