Well If it isn't the hop up, which it might still be. My guess is you have your scope on the wrong way, I had this problem at first because of the directions. Basically the post that controls elevation should be on the top and the post that controls wind-age(left-right) should be on the right on the side of the bolt handle. That just may be your problem because then all the adjustments are going the opposite way they are supposed to. I am just assuming you made this easily fixed mistake and your hop up bucking is not damaged or improperly aligned. But these guns and their permutations of similar brands generally shoot 450-470fps, UTG does make an upgrade kit if you want more power.
Heres my link to of a review i did of the upgrade if your interested: http://miairsoft.proboards.com/index.cgi?board=spring&action=display&thread=31882
Heres my link to of a review i did of the upgrade if your interested: http://miairsoft.proboards.com/index.cgi?board=spring&action=display&thread=31882