Hey, BP,
Glad to hear of your purchase, considering what I was doing with a Shadow tonight, I know you'll be happy with it, especially after a GRT trigger and a decent scope. Don't remember if I already told you this, but I really like the Leapers 3-12x44 AO full size. Don't take this wrong, but your choice in targets seems a little indiscriminate. If I were you, I think I'd want to be a little more sure of my target ID before I shot. You could be shooting birds that have Federal protected status. That includes most birds classed as song birds. From the description you gave, the birds you shot could be Swainsons Thrushes, protected, or Starlings, major pest and one of my favorite targets. So do yourself a favor, and get a decent bird book. Or stick to birds you know are pests. BTW, what pellet did you start with? And do you have a selection to test with? FWIW, I was shooting tonight with JSB Exacts, 4.52 and 4.53 head diameters. The 4.52's seemed just a hair better, but I was having an "on" night. Check out my post on the Gamo forum. Later.
Dave