I have not shot Hydra-shok ammunition from my 40 caliber P99. However I have shot the improved HST (Hydra-shok two) 40 caliber in the second generation P99 without any problems. Accurate, no jams. The recoil is brisk but controllable.
The Hydra-shok is a proven but older bullet technology. Federal supposedly improved the design with the HST. I have yet to actually shoot it into flesh so I do not know how it performs. However, come to think of it, I never fired the old Hydra-shok bullets into flesh to compare it to. I guess I am just lucky to not be in fire fights on a regular basis.