How to make a part move in a direction forever?

So, i'm improving my gun script and I need a bullet to move forward facing the position of anyCFrame.p. I need help lol.

Here's an awesome projectile script I made! It is completely functional under a LocalScript but you can work to configure it so that it replicates it to the server!

local Workspace = workspace or game:GetService("Workspace")
local Players = game:GetService("Players")
local RunService = game:GetService("RunService")
local Debris = game:GetService("Debris")
local UserInputService = game:GetService("UserInputService")

local LocalPlayer = Players.LocalPlayer
local Character = LocalPlayer.Character
local Mouse = LocalPlayer:GetMouse()

local function LaunchProjectile(Origin)
	local Projectile = Instance.new("Part",Character)
	Projectile.Anchored = true
	Projectile.CanCollide = false
	Projectile.BrickColor = BrickColor.new("White")
	Projectile.FormFactor = 3
	Projectile.Name = ("Projectile")
	Projectile.Material = Enum.Material.Neon
	Projectile.Size = Vector3.new(1,1,1)
	Projectile.Transparency = 0
	Projectile.TopSurface = 0
	Projectile.BottomSurface = 0
	Origin = (typeof(Origin) == "Vector3" and CFrame.new(Origin)) or (typeof(Origin) == "CFrame" and Origin)
	Projectile.CFrame = Origin
	local Scale = .1
	local PositionId = 0
	--coroutine.resume(coroutine.create(function()
		Projectile.Anchored = false
		local DirectionalPart = Instance.new("Part",Workspace)
		DirectionalPart.Anchored = true
		DirectionalPart.CanCollide = false
		DirectionalPart.Name = ("Direction")
		DirectionalPart.Material = Enum.Material.Neon
		DirectionalPart.Transparency = 1
		local RayObject = Ray.new(Origin.Position,(Mouse.Hit.Position - Projectile.CFrame.Position).Unit * 500);
		local Hit,Position,Normal = Workspace:FindPartOnRay(RayObject,Projectile)
		DirectionalPart.BottomSurface = 10
		DirectionalPart.TopSurface = 10
		local Distance = (Projectile.CFrame.Position - Position).Magnitude
		DirectionalPart.Size = Vector3.new(.1,.1,.1)
		DirectionalPart.CFrame = CFrame.new(Projectile.CFrame.Position,Position) * CFrame.new(0,0,0)
		Projectile.CFrame = DirectionalPart.CFrame
		DirectionalPart:Destroy()
		local BodyVelocity = Instance.new("BodyVelocity")
		BodyVelocity.MaxForce = Vector3.new(1e9,1e9,1e9)
		BodyVelocity.Velocity = Projectile.CFrame.LookVector * 125
		BodyVelocity.Parent = Projectile
		local HitDebounce = false
		Debris:AddItem(Projectile,15)
		wait()
		local HitEvent = Projectile.Touched:Connect(function(Hit)
			if HitDebounce == true then
				return
			end
			HitDebounce = true
			--[[
				Do hit stuff here.
			]]
			HitDebounce = false
			Projectile.Anchored = true
			Projectile.Transparency = 1
			wait(8)
			Projectile:Destroy()
		end)
	--end))
end

UserInputService.InputBegan:Connect(function(InputObject,GPE)
	if GPE then
		return
	end
	if InputObject.UserInputType == Enum.UserInputType.MouseButton1 and InputObject.UserInputState == Enum.UserInputState.Begin then
		LaunchProjectile(Character.Head.CFrame * CFrame.new(0,3,0))
	end
end)

raid6n had the correct version of this code but I'm just adding CFrames to it since that's what you wanted.

while true do
    local part = script.Parent
    part.CFrame= CFrame.new(part.Position) * CFrame.new(0,0,1) --the number depends on which direction it's going
end

You can also use lookVectors to make it continue in the direction it's going but I'm not so good with those.

Simply lerp the parts CFrame in a loop such as a Heartbeat loop or a While loop.