Why is this script working in play solo mode but not in server?

So this is where the script is set at: Pistol(Tool) > LocalScript

Script:

Player = game.Players.LocalPlayer
Gun = script.Parent --Tool(Pistol)
Ammo = Gun.ammo.Value -- there is an intvalue called ammo and it value is set at 10
Clips = Gun.clips.Value -- then is an invalue call clips andit value is set at 2
mouse = Player:GetMouse()
BulletDamage = 10
enabled = true

function onEquippedLocal()
	Player.PlayerGui.GunGui.FrameforGun.Visible = true
end
function unEquippedLocal()
	Player.PlayerGui.GunGui.FrameforGun.Visible = false
end
Gun.Unequipped:connect(unEquippedLocal)
Gun.Equipped:connect(onEquippedLocal)
function Shoot()
	if Ammo >= 1 and enabled == true then
		enabled = false
		IsFiring = true
		Firing()
	end
end

function Firing()
	repeat wait(0.2)
		
		function Damage(Part)
			if Part.Parent:FindFirstChild("Humanoid") ~= nil and Part.Parent.Name == "Zombie" then
				Part.Parent.Humanoid.Health = Part.Parent.Humanoid.Health -BulletDamage
				Bullet:Destroy()
			end
		end
		Ammo = Ammo -1
		Player.PlayerGui.GunGui.FrameforGun.NumberLabel.Text = ""..Ammo
		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()
	if enabled == true and Ammo < 20  then
		enabled = false
		if Ammo == 0  then
			wait()
			Player.PlayerGui.GunGui.FrameforGun.Reloading.Visible = true
			wait(0.7)
		    Player.PlayerGui.GunGui.FrameforGun.Reloading.Visible = false
			Ammo = Ammo +10
			Player.PlayerGui.GunGui.FrameforGun.NumberLabel.Text = ""..Ammo
			Clips = Clips -1
			Player.PlayerGui.GunGui.FrameforGun.NumerLabel.Text = ""..Clips
			
			if Clips == 0 then
				Ammo = Ammo -10
				Player.PlayerGui.GunGui.FrameforGun.NumberLabel.Text = ""..Ammo
				 Player.PlayerGui.GunGui.FrameforGun.Reloading.Visible = false
				script.Disabled = true
			end
		end	
		enabled = true
	end
end
mouse.KeyDown:connect(Reload)
Gun.Deactivated:connect(StopShooting)
Gun.Activated:connect(Shoot)

Thanks for helping! My error is: 07:46:28.975 - ammo is not a valid member of Tool 07:46:28.975 - Script 'Players.Player1.Backpack.Pistol.LocalScript', Line 3

Sometimes when I have an issue with scripts working in solo/test mode but not in a normal server I switch script types and that sometimes fixes it depending on the situation. However since you have an error you can try this:

Player = game.Players.LocalPlayer
Gun = script.Parent --Tool(Pistol)
Ammo = Gun:FindFirstChild("ammo")
if Ammo ~= nil then
	print("Ammo exists in script.Parent")
	Ammo = Ammo.Value
else
	print("Ammo does not exist in script.Parent")
end

Hopefully that will show you if for some reason the 'ammo' object is not where the script thinks it is. Make sure it's not capitalized or anything and that you've given the correct path.