I'd suggest that if you're gun is shooting accurately to just leave it alone. Your gun (if I have the right model) is rated at 900 FPS with alloy pellets, which translates to a likely 700+ FPS (or so) with average 14-15gr lead (I'm probably a little conservative in my estimate). As long as your gun is functioning as specified, there's not too much you can do to make "big" gains (you could rebuild, relube, lap tight spots out of the barrel, etc for small gains in velocity, and big gains in smoothing the action). If you run it over a Chrony and find it shooting especially slow, or with really big extreme spread numbers, and/or accuracy is really bad, a rebuild would likely restore it to full power. If you NEED more power than that (already pretty powerful) gun puts out, you may want to start looking into PCPs. The Discovery is a decent entry level PCP, can be pretty easily charged with a hand pump, and doesn't break the bank. Mine shoots 15.89 JSBs in the (middle, if memory serves) 800 FPS range.