Location of weapon worldmodel clientside & weird renderbounds

[Lexic]

I'm trying to set the renderbounds of a SWEP I'm making that fires a beam at another entity.
However, when I call GetPos on the SWEP, it returns the player's crotch.
I solved that by using the hand bone like this:
    local bone = self:LookupBone("ValveBiped.Bip01_R_Hand")
    local matt = self:GetBoneMatrix(bone);
    local pos = matt:GetTranslation();

    pos = pos
        + matt:GetForward() * 5
        + matt:GetRight() * 5;

    self:DrawMagicBeam(pos);
But that doesn't help me when setting the render bounds. I tried debugging the issue in thirdperson with this code
function SWEP:Think()
    local min, max = self:GetRenderBounds();
    local pos = self:GetPos();
    local centre =  self:OBBCenter();
    local t = FrameTime();
    debugoverlay.Cross(pos, 5, t, color_white, true);
    debugoverlay.Cross(self:LocalToWorld(centre), 5, t, color_red, true);
    debugoverlay.Cross(self:LocalToWorld(min), 4, t, color_green, true);
    debugoverlay.Cross(self:LocalToWorld(max), 4, t, color_blue, true);
end
Which shows two(!) max bounds:

https://i.imgur.com/6cn1uDT.png

I also tried displaying them with
    debugoverlay.Box(pos, min, max, t, color_white, true)
which results in two hard to see boxes:

https://i.imgur.com/dbFefKR.png

What am I doing wrong here?
Full SWEP code on github