I tried Hdgdon HP-38 and Alliant Power Pistol powders for my 9 mm reloading. There was a major difference in recoil between the two. I put the Power Pistol on the shelf. I am reloading for non sanctioned IDPA club meets and don't have to meet a "power factor" and I don't need the extra recoil the Ppower Pistol delivered.
BTW. A double charge of 4.6 grains of HP-38 in a 9 mm case will be obvious. It won't overflow the case but if you take the time to take a peak at it, you will see that the case is almost completely full rather than about half full.