I have also loaded the 190 HP from GT and did some testing with water jugs. These soft bullets will expand in a water jug down to 700 fps. I know its not a scientific test, but compared to the Hornady SWCHP, the GT Bullet will expand at a lot lower velocity and they shoot really accurate in my 3" Model 696Groo here
I also have one.
I have shot it with full pressure 240gr loads [Magtec]
I find the gun works just as well with keith 44 spec loads or lighter.
I like the GT 190 gr SWC Hp bullet for smaller things and GT says
the hp will work at 700fps or faster "impact" speeds.
Also , a WC at 700 to 800 should handle most SD or
things up to big dog just fine...