Ive been happy with my QB altho it seemed alittle shy on power.
Well after months of reading about mods I finaly took mine apart,spur of the moment actually,and was shocked at what I found.
The hole on the bottom of the bolt (entrance port?) was just barely drilled through.Kind of a diamond shaped hole from the tip of the bit I guess,barely 1 mm at the longest point.
The "airhole" in the bottom of the top tube was mostly blocked with a large metal filing or flake.
The seal that can be replaced with 1/.4" tubing was squashed mostly closed.
Wont go into the stripped screws.
I was kinda shocked,it looked so good on the outside.
Anyhow,I cleaned stuff up,finger twirled a drll bit in the squashed seal (will replace with tube next time) and drilled the probe out with a 5/32 bit.Both the bottom hole and the probe its self.
Popped it back together,only takes a few minuits (didnt take out the valve) and holey-smokes,it shoots with some authority now.
I dont have a crony but the difference is amazing.
Accuracy is still amazing,shot count about the same,52 or 3 then starts dropping.
So the moral here is if you havent taken yours apart,do so,you dont know what you might find.