Some info to add... I concur with the previous post about the SGM .29 measurements. My measurements were almost spot on with what was found. Overall, they are the best bb.
Here is a little mini addition to this..
Hardness -This is more important than you would think, for several reasons. First of all, a softer BB is going to tend to deform more easily with natural elements quicker than one that is harder. Second, when forced around by your loaders and tension from springs, nozzles etc, they tend to nick and chip very easily. One good example of this are madbull BB's. I gave up on them completely because of how soft they are. The problem is that everything they come in contact with(speed loaders, magazine plastic, plastic and metal air nozzles) are all much harder than the material its self. The other issue with these is their construction, but we will address that in another section.
The easiest way to test hardness is a scratch test. By holding the BB with Teflon wrapped needle nose, and using a pinching dike, i measured how much material scratched off, and how easily. It's not a truly scientific way to do it, but the results were pretty clear cut and obvious.
The following are in order from hardest to softest.
1. Bioval .27(clear) BBBMAX
2. Maruzen SGM .29(white)
3. Bioval .30(white)
4.Goldenball .30(white), Goldenball .30(black)
5. Madbull .30(white)
6. Madbull .36(green)
7. Madbull .43(tan)
I really hate to even list the madbull's with the rest of those because they are in a whole other, crappy league. The Bioval clears are made of a resin that makes them impervious to deflection of energy, instead they just shatter if anything.
Maruzen SGM .29's and the Goldenball .30 series are VERY VERY similar in size, weight(.3g of difference on avg), and composition.
The madbull .30, .36, and .43 are about the same hardness, which is very very soft.
Composition / air bubblesI took a batch of 10 bb's from every one listed above and attempted to cut or break them in half. Here are the results.
Bioval .27 Clears cannot be cut, they shatter, like glass. They have zero air bubbles.
Maruzen SGM's break clean in half every time, and have zero air bubbles as well as a solid composition.
Bioval .30's are basically identical to the SGM's and contain zero air bubbles.
Goldenball .30's follow with just a slightly less dense composition than the SGM and Bioval's, but with no air bubbles present.
Madbull .30, .36 and .43 all contain a center air bubble and sometimes smaller additional ones. They are so soft that when 'breaking' them, they just smash instead.
You can see in the photos below the madbull .43(tan), a goldenball .30 (black), a bioval .30(white, right), and a Maruzen SGM .29(white, left)
I have noticed a lot of people are finding greater success in AEG's and GBBR's by switching to a BB in the .27 to .30 range. As long as you are shooting 380 to 400 I think this will tighten up those groupings a bit more at long ranges. .20's and .25 are just too light.
