Terrible with math, need some help with rotations and velocity.

I'm currently scripting a gun system and I'm having some issues with the shell ejection. With the gun positioned correctly on the x-axis, the ejection works fine; the shell is rezzed and flung up and backwards along the x-axis.

However, when the gun is rotated in any way a problem appears, the shell is still ejected as if the gun were perfectly aligned and stationary.

I'm aware that this is due to the velocity parameter on llRezObject but I'm not even sure where to start calculating to always make the shells fly out in the right direction..

Here's my current code:

            vector vRezPoint;
            
            vRezPoint = llGetPos();
            vRezPoint.x += 0.10;
            vRezPoint.z += 0.10;
            
            llRezObject("shell", vRezPoint, <2,0,0>, llGetRot(), 1);

Figured it out.

For those wondering, the correct method is:

            vector vRezPoint;
            vector vRezVel;
            
            vRezPoint = llGetPos();
            vRezPoint.z += 0.05;
            
            vRezVel = <0,2,-1> / llGetRot();
             
            llRezObject("shell", vRezPoint, vRezVel, llGetRot(), 1);