and a discussion here: https://www.muscleforlife.com/hmb-supplement/
I can’t find the full study but basically it says that HMB free acid doesn’t really have much benefits.
I think the research by Wilson et al (commissioned by MuscleTech as I recall) suggesting HMB FA produces crazy improvements in muscle mass and performance is an outlier amongst other HMB data.
HMB has a small, but potentially useful effect- but I don’t think HMB FA is way better than HMB chelated to something like calcium.