This is a post I made elsewhere some time ago but still valid. “Having to drop below 14 lbs due to an injury, I did a fair amount of research on this. Some balls such as Radical Gurus, Motiv Trident etc are not made in weights less than 14. That said, the best explanation of the issue I got from a manufacturer was Storm. Their website posts a picture of the core used in each weight for each ball and some balls are a completely generic core and some like Alpha Crux use same shape core as 14-16. Storm explained..."This has to do with the density of the core itself. The 14-16 pound balls need the heavier weight block to create the ball. Those cores are very dense and cannot be put into the lighter balls. The lighter balls need less dense cores but the shape doesn’t match up closely to the RG and differential values so we have to find a shape along with the correct density to be able to make that ball in the lighter weights. In your question, the shape of the Catalyst weight block matches up with the RG and Differential values when at a lighter density. If the shape does not, we have to put that generic shape in to get those numbers to match up correctly. Surface composition and texture is still the #1 most influential variable in ball motion. This is kept the same for all weights. Just remember, our shapes have to match up with the limits of RG and Diff that USBC permits. This means sometimes we have to put in that generic shape to stay within this range."
Brunswick said they "use a generic core shape with a RG-differential that is close enough to the 14 to 16 pound shape so the same drilling instructions can be used." I assume Radical does the same.
Motiv said they always use the high tech core shape but modify it for the lower weight
Track, Columbia use specially modified symmetric for lighter weightsâ€
Myself, being speed dominant, low rev, I wanted the strongest 13 lb Assym I could find and that was the Storm Sure Lock. I have had some Motivs too, don’t really look at any other makers anymore or at least, right now