first thing. get it chrono`d, next, clean barrel, if power is ok and consistant, then enter the world of pellet testing, if you want to eliminate problems with your shooting, clamp it in a workmate and shoot 5-10 pellets into paper at about 30 yrds, if you get a good group then its you thats not doing the job, AA s400`s are usually spot on, if that does`nt cure it, go onto the AAOC and see if there is someone close to you who could give it a once over (if the AAOC is up and running, they are having problems at the moment)