How do I make force fields last infinite?

If you want to give a player an indefinitely lasting force field, you have to insert a new force field into their character.

The code below gives the player an infinite force field every time their character spawns.

game.Players.PlayerAdded:Connect(function(plr)
	plr.CharacterAdded:Connect(function(char)
		local field = Instance.new("ForceField")
		field.Parent = char
	end)
end)

Although, force fields aren't the only way to avoid team-killing. You can have the weapons check for the holder's team, and the team of player who gets hit, and determine whether or not the player should take damage.

Good luck with your further development! :D

~Sethex, aka. TheWaterFoox