Abstract: The gun comprises a body having a downwardly extending grip (2) and an assembly comprising a heating block (4) having a vertical axis, a first envelope (5) defining with the block a sinuous path for heating air, and a second envelope (6) defining a path for paint. The second envelope (6) is in the shape of a bell and is pivotally mounted on top of and around the first envelope (5). The first envelope (5) and second envelope (6) define therebetween a chamber (45) which communicates with the paint path and has an outlet conduit (46) which extends through the heating block (4) and communicates with a rotary spraying head (T) mounted on the front end of the body (1). A vertical hot air passageway (28) coaxially surrounds the outlet conduit (46) and communicates with the sinuous path for heating air and also communicates with the spraying head. The second envelope (6) has a lateral boss (39) defining a passage which communicates with the path for the paint.