If its scoped I would suspect the scope to be the accuracy problem. Spring piston air rifles are extremely hard on scopes. More so than even large magnum CF rifles.

Scopes and mounts often fail because of the forward and backward motion associated with them.

Also make sure the lockup between barrel and action is tight and replace barrel seals often. This will keep the lock tighter. Seals are easy to find, easy to change and cheap.

I shoot a Gamo Hunter and its probably killed several hundred squirrels, a feral cat or two and countless pest birds.

For serious trigger upgrades consider the GRT-4g trigger. It costs around $35 and fits most SP air rifles. Huge difference in let off and improves accuracy as well. Its a DIY project that might take 10 minutes to install. This guy know air rifles..........

http://www.charliedatuna.com/