I don't know. I currently have the Theoben installed in the .22 cal. CFX. I have to put it through the chrony soon. I was hoping to do it tomorrow (Saturday) but I might be busy with other stuff.
When it still had the Whisper gas ram in the .22 CFX, it was shooting 11.9 grain pellets at 725 fps, 14.3 grain wadcutters at 650 fps and 16 grain Predators at 680 fps.
I have the Whisper gas ram installed in the .177 CFX. The .177 CFX with the Whisper gas ram shoots 7.0 grain pellets at 925 fps and 7.9 grain pellets at 870 fps.
The gas ram or either caliber is the same.