Kinda irrelevant to this thread but I have to mention that I was able to get an HW55 piston from JG Airguns. Having looked everywhere I was just thrilled to find it. I bought an HW55T that looked good but when I shot it I was crestfallen that it just shot so poorly, roughly. Just not what you'd expect from a 55. Got it apart and found someone had replaced the original piston with something far more massive, longer and heavier. I've tried buttoning the piston, different springs but could not get it to shoot anywhere near as good as my other 55's. Probably some of that has to do with my lack of skill but I'm really happy to have another go at it with the correct piston.