How would I add a bias to place the drawline in font of the barrel?

Hello,

I'm programming a basic firearm. Following the standard mathematics to develop a drawline function for the trajectory, I have gotten where I have desired to be. However, I was wondering how I would add a bias to the arithmetic to start the drawline in front of the Tool, instead of the handles center. Is there anyone who could fill me in here?

--// Using standard revolver mesh
function drawline(Gun, Position) --// endpos variable of Raycast
	local ShotDistance = (Gun.CFrame.p - Position).magnitude
	local Gunshot = Instance.new("Part"); Gunshot.Parent = workspace
	Gunshot.Anchored, Gunshot.Locked = true, true
	Gunshot.CanCollide = false
	Gunshot.Size = Vector3.new(.2,.2,ShotDistance)
	Gunshot.CFrame = CFrame.new(Gun.CFrame.p + 5, Position) 
    * CFrame.new( --// Same line
		0,0,-1.5 + (-ShotDistance/2)
	)
	game:GetService("Debris"):AddItem(Gunshot, .1)
end

The negative 1.5 is my bias, it puts the drawline in front of the barrel, yet, when I change my shot, let’s say to fire left or right behind me, it moves a few studs away from the barrel. I am not trying to get this affect, but I can deal with it. I was just wondering if there was a way I can permanently keep starting it one stud in front the barrel no matter which direction I fire.

Pathway: Player - Backpack - Tool - Handle (‘Gun’ variable)