Rotation on two Axis?

I’m trying to rotate a Sniper Rifle on a Bipod, I’ve read other posts but they don’t seem to help much. As no matter what I do (Parent + Child, Rotation on Global/Local) it always ends up effecting the Z axis and starts to go weird. What’s a proper way to RotateAround on both Y and X axis?

You can combine different rotations by multiplying quaternions.