HMB

I have not noticed any difference in vascularity, but my recovery and strength are improving nicely.

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.

The best thing that you can do to improve vascularity is to reduce body fat. As the subcutaneous fat layer decreases, the vascular network underneath the skin will be much more visible.

Assuming you're already very lean, the following foods/ingredients can be helpful: citrulline, polyphenols (dark chocolate, grape skin, French pine bark), ginseng, creatine... even sugar (should be limited to small amounts around workouts).

While many people also use arginine for enhanced blood flow/vascularity, the supporting science for this is weak - especially if you're already consuming enough arginine through high protein foods. Moreover, the more arginine you consume, the less effective you become at converting it to nitric oxide. That's why most arginine-containing N.O. products don't work as well after a few days/weeks.