A syringe for injecting solid, hard and rough granular material includes: a longitudinal injection chamber having constant section and an internal diameter of less than 4.5 mm, having a distal outlet mouth for the flow out of the material, whose surface is the same as the injection chamber, and a proximal mouth, in which granular material is inserted； a plunger sealedly mobile along the injection chamber, joined to a stem which enters the injection chamber through the proximal mouth, the plunger having: a transversal section which sealingly couples with the surface of the injection chamber, and having an operative surface, facing towards the distal mouth of the injection chamber； and a body projecting longitudinally internally of the injection chamber, fixed substantially axially to the operating surface of the plunger, having a diameter that is less than 70% of that of the injection chamber and a length greater than 6 mm.
