People underestimate the effect of proper airseal on higher-powered rifles. You'll lose easily 15-20% of the fps from the spring if you don't have the right tweaks done. teflon tape, anti blowby rings, and correct o-ring seal with the hop up unit come to mind. Based on that fps, looks to me like you got all of the right "tweaks" done! 
Just make sure not to use that on a field!
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Just make sure not to use that on a field!
