Hello guys

There's something my friend Seven7 and I don't understand.

I've a Xvalve with ult on my rpg mag.

When I use it with a HP tank, it leaks by the barrel, when I use it with a SHP tank, it works perfectly.

The on/off orings are lubed and in good shape.
We checked and cleaned every part of the on/off.
I even tried to change the on/off

Have you ideas ?