How do I make mags in this gun script?

I am make a gun and everything is perfectly fine but i need to make mags in this script and I don't know how. Here is the script:

Player = game.Players.LocalPlayer
Gun = script.Parent
Ammo = 20
MaxAmmo = 20
mouse = Player:GetMouse()
BulletDamage = 10
enabled = true
function Shoot()
	if Ammo >= 1 and enabled == true then
		enabled = false
		IsFiring = true
		Firing()
	end
end

function Firing()
	repeat wait(0.3)
		
		function Damage(Part)
			if Part.Parent:FindFirstChild("Humanoid") ~= nil and Part.Parent.Name ~= Player.Name then
				Part.Parent.Humanoid.Health = Part.Parent.Humanoid.Health -BulletDamage
				Bullet:Destroy()
			end
		end
		Ammo = Ammo -1
		print("You have "..Ammo.." ammo left!") 
		enabled = false
		Bullet = Instance.new("Part", Workspace)
		Gun.GripPos = Vector3.new(0,0.3,0)
		game.Debris:AddItem(Bullet,2)
		Bullet.Shape = "Ball"
		Bullet.Size = Vector3.new(0.1,0.1,0.1)
		Bullet.TopSurface = "Smooth"
		Bullet.BottomSurface = "Smooth"
		Bullet.BrickColor = BrickColor.new("Really black")
		Bullet.CanCollide = false
		Bullet.CFrame = Gun.Handle.CFrame
		Bullet.CFrame = CFrame.new(Bullet.Position,mouse.Hit.p)
		BM = Instance.new("SpecialMesh",Bullet)
		BM.MeshType = "Sphere"
		BM.Scale = Vector3.new(0.2,0.2,0.2)
		v = Instance.new("BodyVelocity", Bullet)
		v.velocity = Bullet.CFrame.lookVector *90
		v.maxForce = Vector3.new(math.huge,math.huge,math.huge)
		Fire = Instance.new("Sound", Bullet)
		Fire.SoundId = "http://www.roblox.com/asset/?id=131419157"
		RP = math.random(10,20)
		RP = RP/10
		Fire.Pitch = RP
		RV = math.random(70,90)
		RV = RV/10
		Fire.Volume = RV
		Fire:Play()
		game.Debris:AddItem(Fire, 2)
		Bullet.Touched:connect(Damage)
		wait()
		Gun.GripPos = Vector3.new(0,0,0)
		enabled = true
		
	until IsFiring == false or Ammo == 0
end
function StopShooting()
	IsFiring = false
end

function Reload(key)
	key = key:lower()
	if enabled == true and Ammo < 20 and key == "r"  then
		enabled = false
		RS = Player.Character.Torso["Right Shoulder"]
		for i = 1,4 do
			RS.C0 = RS.C0 *CFrame.Angles(0,0,0.2)
			wait()
		end
		
		repeat wait(0.1)
			Ammo = Ammo +1
			RS.C0 = RS.C0 *CFrame.Angles(0.2,0,0)
			Shell = Instance.new("Part",Workspace)
			Shell.TopSurface = "Smooth"
			Shell.BottomSurface = "Smooth"
			Shell.Reflectance = 0.01
			Shell.BrickColor =BrickColor.new "Black"
			Shell.CanCollide = false
			Shell.Size = Vector3.new(1, 1, 1)
			ShellMesh = Instance.new("BlockMesh",Shell)
			ShellMesh.Scale = Vector3.new(0.2,0.3,0.45)
			game.Debris:AddItem(Shell,0.8)
			Shell.CFrame = Gun.Handle.CFrame *CFrame.new(0,-0.5,-0.3)
			wait(0.1)
			RS.C0 = RS.C0 *CFrame.Angles(-0.2,0,0)		
		until Ammo == MaxAmmo
		for i = 1,4 do
			RS.C0 = RS.C0 *CFrame.Angles(0,0,-0.2)
			wait()
		end
		wait()
		enabled = true
	end
end
	
mouse.KeyDown:connect(Reload)
Gun.Deactivated:connect(StopShooting)
Gun.Activated:connect(Shoot)

Please help THANKS!