How Do I Change it's Rotation

I'm using the below script in a child prim of a gun I made. The shell rezzes from the right position and follows the correct path. However I want to change the rotation of the shell 90 degrees when it is rezzed and falls. Can someone please tell me where in the script, so I don't mess it up with trial and error? Thanks

default
{
state_entry()
{
}

link_message(integer sender_number, integer number, string message, key id)
{
if(message=="fire"
{
rotation my_rot = llGetRot();
vector my_fwd = llRot2Fwd(my_rot);
vector pos = llGetPos();
rotation rot = llGetRot();
vector offset = <-1.0, -0.5, 1.0>;
vector vel = <0.0,-0.87,0.0>*llGetRot();
offset *= rot;
pos += offset;
llRezObject("shell", pos, vel, my_rot, 1);
}
}
}

i think i figured it out thanks anyway