Korger is right. There's really nothing in HMB that should increase vascularity. HMB is a metabolite of leucine, so the results that you should expect to receive will be similar to those of BCAAs, in particular leucine (i.e., increased lean mass, reduced muscle soreness, delayed mental fatigue during endurance exercise, faster recovery, and perhaps even reduced midsection adiposity.)
For these reasons, HMB and BCAAs (stick with the later, if on a budget) are great additions for any athlete whether strength or endurance focused. However, if it's increased vascularity that you're after, there are much better choices out there.