I went through much the same thing. Here's what I learned:
[ul][*]My SS/Laminated Omega does not like powerbelts, regardless of bullet weight or amount of powder or number of pellets[*]Hornady SST's shoot decent, but are a b*%^h to load[*]My gun shoots saboted 300 grn bullets much better than 250's[*]APP Shockey's gold shoots well and cleans easy[*]Shockwaves load easier than Hornadys[*]Remington Kleanbore primers did nothing to improve the crud ring when I used 777 pellets
[/ul] I started working on loads beginning with the 300 grain shockwaves and 110 grns of APP and got some decent groups. I need to try some different volumes of powder and see how that goes. I tried to do this last saturday, but the wind kicked up and it started raining before I could do much else. I would say to give the 300 grn shockwaves a try, as well as the APP shockey's gold. You can buy both at most any Gander Mountain if you have one nearby.

Hope this helps
Bill