Is my scope shot?

I recently bought a Marauder pistol, and put on an old RWS scope I had lying around. It used to be on an RWS 34 I had, but I replaced it with a Hawke scope because I couldn’t group with that scope. I didn’t do a whole Hell of a lot better with the Hawke, so I just kind of chalked it up to being a poor springer shooter. Anyhow, I attempted some groups a week ago with some pellets I had lying around, and results were a little disappointing. JSBs didn’t group, and Beeman FTS grouped okay, but not as well as I would have hoped. During the testing, I used up all of my Beemans, so I ordered more, and picked up some H&N FTTs locally yesterday to try out while I wait for the Beemans to arrive. Many people have stated these shoot the best out of their P-rods, so I was pretty excited to try them out. So today I loaded the magazine, gassed up the gun, and shot some groups at 25 yards. Not good. I had groups ranging in size from 3/8ths of an inch up to almost 2 inches. Not only that, but I would shoot a group, take out the clip, reload it, gas up the gun (every 3 clips), and when I went to shoot the next group, the gun would be shooting to either the left or the right of where it was on the last clip. I thought maybe this was due to pressure change, but from 2700 psi down to 1800 psi it would stay in the same general 1 1/2 to 2 inch area over 3 clips, so I don’t think it is changing with pressure. There is absolutely NO consistency in groups, either. I might stack 3 in a row, and then the next shot is an inch to the right, and then the next two stack an inch to the left of the original 3 shots. Attempting to adjust the scope is just as frustrating. The vertical clicks seem pretty consistent, but the horizontal is very inconsistent. I might make 8 clicks and the POI moves a quarter inch, and then 8 more clicks moves it 2 inches. I made sure I was being as consistent as possible, trying to eliminate any sources of error. Here are the variables I was sure to control:
-Scope rings were tight.
-Consistent cheek weld every time.
-Shot from a stable rest.
-Gassed up every 3 magazines.
-Shot in an area that is relatively protected from the wind.
-Took out my Talon SS and shot it with ammo it likes. One ragged hole at 25 yards, so I know I was being consistent.
-Checked the baffles and endcap for clipping. Not clipping as far as I can tell.
So, is my scope shot, or am I doing something wrong? Is there something else I should be checking? If it is the scope, as I suspect, can I repair it, or am I just better getting a different scope?
Thanks in advance for your help,
Chris