A while back, I posted this:
http://www.ar15.com/forums/t_6_54/455836_Gamo_Whisper_Wandering_Zero_Problem_.html
TL;DR: Gamo Whisper with a wandering zero. Would group 2-3 shots, then POI would shift and it would group 2-3 shots in a different place. Lather, rinse, repeat.
One possible remedy I found was to clean the barrel. So, I did. And finally, this past weekend, I had a chance to get out and shoot it.
I have to say, there was much improvement. It is still not where I want it to be, but instead of the groups shifting, they are largely in one group about 2"@25 with an occasional anomalous shot about 1-2" away from the rest of the group. But, it is now actually shootable and I think if I clean it again, maybe the groups will tighten up even more. I even hit a 1 foot square steel target at 100 yards several times with it just for giggles.
If I can get this thing making even 1" groups at 25 yards, I'll be happy. Funny thing is, I originally got this thing back during the post Sandy Hook crisis as something I could shoot that was cheap and had readily available ammo, but I can see that even if .22 isn't hard to find, that shooting airguns still has an appeal of its own.