J_Mac:
You are correct. This idea goes back a long time. In the past, the cores had the same differential values, regardless of ball weight. If memory serves me correct, the Brunswick Quantum balls were the first balls to use different cores, depending on
ball weight, in an effort to replicate ball dynamics.
As to Bowlingman's original observation, it appears that Ebonite uses lower differential cores on most of their 16# balls, when compared to other ball manufacturers. I believe, but I am not sure, that this is due to Ebonite's use of
different coverstock/core materials than some of the other manufacturers .
I do not believe that it diminishes performance . For example, I have a good friend
who uses the Ebonite family of balls exclusively. He was encouraged to try another
popular "brand". He purchased 4 different pieces from the other company. At the end of the day, neither of us noticed any significant difference in performance, when compared with the Ebonite brands.
In addition, there are times when a particular ball's core specs. will fool you. For example, since I am speed dominant (with a lower rev rate), I never used to have
any luck with high Rg cores. They would simply go too long. As a result, I
avoided balls with Rgs above say, 2.52. At the last Ebonite Demo day, that "theory" changed when I tried the Track Tour X, which has a very high Rg core (2.58).
I was surprised how this ball performed for me. This ball never overshot the breakpoint when in the past, I would've needed another 10 feet of lane to get a 2.58 core to turn the corner regardless of the coverstock.
In contrast, my Columbia Crazy Antics has a larger "motor" (differential), and a much lower RG than the Tour X, but it needs another 5 feet of lane to even begin to think about turning the corner, even after I had tried a multitude of different surface
changes.
So in the end, a ball's specs will give you only a general idea about its expected performance, but until you actually roll it, you can never be certain that the specs.
will live up to your expectations. There are just too many variables involved-- coverstock strength, core material used, etc, etc.