the invention relates to an improved design for a spray gun and application system for cold gas dynamic spraying . the gun includes a rear housing comprising a powder inlet and a gas inlet , a front housing removably affixed to the rear housing and comprising an mixing cavity therein for mixing of the powder and gas and an exit therefrom , a nozzle holder having a bore disposed therethrough and removably affixed to the front housing , and a polymeric nozzle positioned within the nozzle holder , an interior taper of the nozzle holder bore complementing an exterior taper of the nozzle . the nozzle having an initially converging , subsequently diverging centrally disposed bore therein adapted to receive the mixed powder and gas from the mixing chamber and the nozzle holder including a cooling jacket which is thermally coupled to the nozzle adjacent the nozzle inlet and mechanically coupled downstream of the nozzle inlet .