Help Sighting in Prowler 177

Hey Guys,
I recently bought a Prowler in 22 and loved it so I bought one in 177. The 22 is signted in fine, no issues but the 177 I cannot get to sight in at all. Ive tried 8 different pellets and shot about 150 times and im still 1-2inches off and no consistency. Is it the barrel?, pellets? scope? Ive tried 2 different 4x32 on it and neither can adjust low enough to get zeroed. Any help is appreciated. Im a novice but shoot 22lr and 17hmr long range so im not a complete newb. Thanks!