I live in the Finland so I can understand that you'd rather learn to tech the gun yourself. I'm not personally familiar with teching e-/x-mags, but I
interesting indeed! VERY nice one!
any idea on what year (aprox) it could be from?
It means that the bolt moves the ball more gently to the barrel when using a stiffer spring. Depending on the spring stiffness the gun won't cycle below