How do I get the right surface for my bulletholes?

So I'm trying to make bullet holes for my gun. I got the position right, but I can't seem to find the right surface the bullet decal should be on. Right now, it choses the surface based on the mouse. So when there's a wall in between the player and the mouse position and the mouse is pointed at the ground, the decal will be facing upwards, while it shouldn't be, because the bullet never hit the ground, it hit the wall.

So how do I know what is the right position based on a ray coming from the player, to the mouse position? Or is there any other (better) way to do this?

Main problem is at line 31.

Here's the script so far:

    local vCharacter = Tool.Parent
    local vPlayer = game.Players:playerFromCharacter(vCharacter)

    local Strike = false
    local mTarg = mouse.Target

    local ray = Ray.new(Tool.Handle.CFrame.p, (mouse.Hit.p - Tool.Handle.CFrame.p).unit * 300)
    local part, position = workspace:FindPartOnRay(ray, vPlayer.Character, false, true)

    local surfaceCF = mouse.Hit

    if part and part.Name ~= "BulletHole" and not Strike then --Check if part exist + I don't want any bulletholes to be created on other bulletholes + Strike is wether it hit a humanoid or not, I don't want bulletholes on humanoids
        local p = Instance.new("Part")
        p.formFactor = "Custom"
        p.Size = Vector3.new(0.5,0.5,0.5)
        p.Transparency = 1
        p.CanCollide = false
        p.Locked = true
        p.CFrame = part.CFrame + (position - part.Position) --The position of the part is right
        p.Name = "BulletHole"

        local w = Instance.new("Weld") --So the bulletholes doesn't fall
        w.Part0 = mouse.Target
        w.Part1 = p
        w.C0 = part.CFrame:inverse()
        w.C1 = p.CFrame:inverse()
        w.Parent = p

        local d = Instance.new("Decal")
        d.Parent = p
        d.Face = mouse.TargetSurface --This is where i don't know what to do
        d.Texture = "http://www.roblox.com/asset/?id=64291961"
        p.Parent = game.Workspace

        delay(5, function() 
            for i = 1, 100 do
                wait()
                d.Transparency = d.Transparency + 0.01
            end
            p:Destroy()
        end)         

    end

Any help is appreciated. C: