Airgun shot string

Load photos to a hosting site like photo bucket then copy and paste image code.

Sorry I don't completely understand your string question?

"Hi guys and gals I was wondering where to shoot on a shot sting that just gently went downwards?"
First, fix rifle/pistol so you DO have a "bell curve"

You cant post a picture, how about just beginning and ending numbers, beginning and ending fill psi. What rig?

The more information you can share the better folks will be able to help you.

John

Pick the top of the curve that has all its values within 30 to 50 fps. Or rather: values within however many fps that gives you no noticeable change in point of impact at your maximum shooting distance.
If you shoot on average 800 fps but never past 35 yards, then you can use many more shots per fill than if you shoot out to 70 yards, where a small change in velocity will result in a large change of POI.

If the shot string only goes down but before that never went up, then you seem to be using only half of your optimum fill curve.
I would suggest either filling to a higher pressure, or decreasing the hammer spring tension (HST) a bit, to make the gun "like" a lower operating pressure.