Abstract: A gun is disclosed which is adapted to thoroughly intermix a pair of mutually soluble liquid reactants while pourably delivering the resulting mixture at substantially atmospheric pressure and before any substantial reaction has occurred. The structure of the mixing chamber of the gun is described in detail which structure does not include any baffles or other means impeding the free flow of the reactants through the mixing chamber. The preferred embodiment comprises a disposable tube portion and although the gun is essentially self-cleaning, a means for introducing a cleaning solvent into the mixing chamber is disclosed.