I have a gamo shadow 1000 and have been having trouble killing my game lately.About two days ago i went out starling hunting,i shot 2 of them in the chest feathers went everywhere and they flew off.I thought maybe my gun was off.No it wasn't,then i thought maybe im using the wrong pellets so i went and bought more pellets for better expansion.I went out again and the same thing happened before with the first bird.After that i started doing head shots and getting my kills, a little bit after hunting starlings i went and checked where i see alot of rabbits at, i saw one and shot it in the head it dropped and didn't suffer.Now im kinda confuses.Do you think the spring is wear in out?