local lp = game.Players.LocalPlayer.Character
local Weapon = "Rifle" -- Your Weapon
lp[Weapon]:GetAttributeChangedSignal("Ammo"):Connect(
    function()
        lp[Weapon]:SetAttribute("Ammo", 9999)
    end
)
lp[Weapon]:SetAttribute("Firerate", 9999)
lp[Weapon]:SetAttribute("BulletSpeed", 9999)
lp[Weapon]:SetAttribute("Spread", 0)