The 135 GD was designed with 7 petals and 800 fps to open up.

The 125gr GD should have just 6 petals and is designed for higher speeds of 905fps or more to open up, due to a heavier copper jacket wall.

My test with the 125gr bullet in my J frame had to reach a K frame pressure to expand c/o 935 fps.
My load with a 2" J frame is at 880 fps with a MV of 215 ft/lbs.

Have fun.