Cliff,
If these are going to be for your new gas Whisper, also try heavier pellets if you can.
Gene or Bob mentioned that gas ram guns seem to do better with heavier pellets, so I tried some. Found it was true with my gas Whisper.
It loves the Exact Jumbo's (15.8 gr) better than the 14.5gr, or lighter pellets, including the JSB Exact Jumbo RS ( 13.3 gr). The lighter a pellet I tried, the worse it shot them.
Second best to the Jumbos is the Jumbo heavies at 18.2 gr.
You may find the same thing with yours if you have any heavies to try.
Paul.