HW13 shot is right at 13g/cc shot. It is round and very consistent on the sizes.
You can get HW13 shot in sizes #6, #4, #2, BB and T shot.
I have reloaded quite a bit of HW13 shot using BPI's Handloading Hevi-Shot manual and RSI's Reloading Heavyweight Shot Reloader's Guide Volume 3.
BPI and Bucks Run both sell the wads that they use in these two loading manuals.