how do mate!
As previously said, I'd say you need a lot more practice on paper before shooting at live quarry mate. Yes it can be frustrating, but you owe it to the bird/animal to give it as quick a death as possible which more than often means a clean headshot.
By testing on paper you will not only improve your shooting but will find out which pellet suits your rifle. If you have a look here http://www.thehuntinglife.com/forums/topic/181320-pellet-swap-opportunity/ you might be able to source some different pellets to try till you find the ones that suit the rifle. The rest is up to you,