What mistake have I made with raycasting?

I've been looking into learning how to raycast for quite a long time now, I've looked through many discussion threads and tutorials, I never fully understood any of them so I decided to just take a crack at it myself.

local RayIgnoreList = {Gun.Model.Muzzle}

EventFired.OnServerEvent:Connect(function(plr,LookVector)
    local Rey = Ray.new(Gun.Model.Muzzle.Position, LookVector)

    local Part,position = workspace:FindPartOnRayWithWhitelist(Ray,{RayIgnoreList})
    print(Part,position)

    local part = Instance.new("Part", workspace)
    part.Position = position

end)

I keep getting the error "Unable to cast value to Object" I found a few different threads asking the same question, but none of those told me what exactly the error meant. So, with no alternatives Im turning to scripting helpers.