With a small diameter bullet, like the 9 mm, hydrashocks may not open reliably at this velocity.
I haven't wetpack tested in the R9S, but did in the similarly short barreled PM9 and various 147 grain 9mm expanded just fine. Modern JHP are engineered to expand at their operational velocity and the old adage that you need XYZ fps (XYZ ~= 1000) for expansion is no longer true. 147 grain 9mm provides some of the best standard pressure 9mm SD ammo from GD, to HS, to Ranger T, to even the lowly WWB 147 JHP personal protection.
(Check the FAQ, IIRC, expansion was tested for some brands of 147 grain JHP ammo -- I know at least one brand since I sent in some Ranger T for testing.)
My R9S went home like ET since it tended to keyhole this weight 9mm and I wasn't happy with that so Karl and the boys are gonna tweak my low number serial numbered gun to improve this. I'm crossing my fingers and holding my breath...