Locally hurting someone to globally hurting someone help?

So I'm trying to hurt a player but the player isn't getting hurt

There are no errors, Filtering Enabled is on, The bullet fires and the module script fires.

Local script:

local bullet = shootbullet(shooter.CFrame.p, mouse.Hit.p)
local damage = math.random(dmgmin,dmgmax)
bullet.Touched:connect(function(hit)
	if hit.Name == "Head" then damage = damage * 3 end
	globmod:hurt(hit.Parent,damage,game.Players.LocalPlayer.Name)	
end)

Module script

local runs = {}
	function runs:hurt(plrname,amount,username)
		if plrname.Parent:FindFirstChild("Humanoid") and plrname.Parent.Name ~= username then
			plrname.Parent.Humanoid.Health = plrname.Parent.Humanoid.Health - amount
		end
	end
return runs

With FilteringEnabled, it basically makes all your local scripts run in their own little world. Which you can take advantage of, and make really neat things. Now, because of this new world being local to the player, that means nothing outside of your computer will see a change your computer made/changed (including other players).

Remote events

This leaves us with remotes. A remote (in ROBLOX) is something that allows communication between all kinds of scripts. We can use the remote event, to command the server to do something a client tells it to do.

Example

I have a pretty good example of how this all works, in my uncopylocked place called "Remote event example" you can check out here:

http://www.roblox.com/games/286802910/Remote-event-example

Now, let's say we have a remote event in the ReplicatedStorage called "Remote". And we have a server script inside the ServerScriptService, that says this:

local RepStorage = game:GetService'ReplicatedStorage'
local Remote = RepStorage:WaitForChild'Remote'

-- You can read about how to use these arguments in my uncopylocked place i provided above.
Remote.OnServerEvent:connect(function(Client, Request, Value)
	if Request == 'damage' then
		-- Code here
	end
end)

And now we can modify your code to look like this:

local bullet = shootbullet(shooter.CFrame.p, mouse.Hit.p)
local remote = game:GetService'ReplicatedStorage'.Remote

local damage = math.random(dmgmin,dmgmax)
bullet.Touched:connect(function(hit)
    if hit.Name == "Head" then damage = damage * 3 end
    remote:FireServer('damage',damage) -- We may need to pass more arguments as well
end)

Hope this helped, if you have any questions let me know.