A little insight - .28 to .30 involves the addition of certain materials (trade secret) to increase the BB weight WITHOUT using compression. Since Stalker has let my cat out of its bag a little (no worries, its worth it to have a good series of tests like this) I can address this a little bit. In .20 to .28 you can use straight bb substrate material (polar bear snot) to gain weight - that however hits a wall at .28 where you are basically faced with a choice - compress your product or use an additive. Compression is bad because after a certain point it it causes the product to become brittle and shatter on impact - which is a safety hazard. It also has a negative effect on spherical balance, causing the material to redistribute unevenly (I'll leave you to draw your own conclusions as to why this is important). Keep in mind there is no direction in which to load a BB - it has to pass through the hopup in whatever position it comes up out of the mag in, hence spherical balance and distribution is critical to consistency - and there is where my primary investment in my product is and is probably the hardest thing to replicate.
Anyways, Stalker is right on the money so far - I've not given him any proprietary information for his testing, which is interesting to watch because he's seeing the results and behaviour of engineering decisions made to make a better more consistent product and his tests bear this out.