[mcguyver]

You guys are way off the mark. Remove your inner barrel and hop chamber from the gun. Turn the hop-up completely off. Put a bb in the chamber and blow. If it comes out of the barrel with barely a puff, your hop rubber is fine. If it takes any kind of effort at all, your hop rubber is either swelled (wrong rubber + wrong lubricant = trouble) or installed poorly.

The notion of gear timing is crap. The first time you pull the trigger, it automatically sets itself. Pistons only "lock back" when they're installed poorly and the guy putting them in let's it twist a bit and it no longer runs in the guides properly. It happens all the time, but if you fail to catch that and let it go, it will come back to haunt you.