I've shot some, but think the velocity quote is wrong. I doubt it's that hot.
When I was an active gun writer, I asked the Federal PR man how fast this load was from both true snub and from three-inch barrels.
He asked an engineer to pull a box of that Hydra-Shok ammo and two S&W M-36's, one in each barrel length.
If I can find his letter, I'll post the results. But I remember the snub gave maybe 825 FPS and the three-inch about 60 FPS more.
Tests I've seen didn't show that bullet opened especially well or drove especially deep, and I rely on Speer Gold Dot 135 grain Short Barrel ammo in short barrels or their 125 grain Plus P from longer barrels, or use the lead HP 158 grain HP, especially in barrels of at least four inches.
Mind you, the 129 grain Hydra-Shok is still probably a pretty good load, and I'd certainly select it over normal lead RN ammo.
Actually, I guess that in longer barrels, some lots may actually reach 950 FPS. If the bullet impacts tough muscle tissue, like the heart, I think the bullet will often open, although if the nose becomes plugged with clothing, expansion is less than certain.
We have good feedback from the street on the Speer Short Barrel load,as it's used by both NYPD and LAPD and the Speer PR man told me that both are satisfied with its performance in real gunfights. That trumps theory and gel tests.
I simply don't have any real shooting reports of the 129 grain Hydra-Shok. But I've carried it in the past and felt reasonably well armed. Still, I was uneasy about having to maybe shoot a large, aggressive dog. Might not penetrate well enough.
Working where I was especially apprehensive about that need and the need to possibly shoot into cars, I carried a .357, loaded with .357 158 grain Hydra-Shok ammo. The Federal PR man at the time told me that it's a good deer load, too, as far as .357 ammo goes in that role from a handgun.
Another very good killer is Winchester's .357 145 grain Silvertip round. I got a detective to check morgue records on how it fared in use by both FBI and with Dallas PD, both of whom issued it to personnel using .357 revolvers. The guy said it was almost too effective. His words. It, by gum, WORKED! Both three and four-inch barrels were involved.
Of course, if you're loading a .38-only gun, that won't affect you...
I hope this is of help.