A method for producing a hollow part (17; 21; 46) made of a metal material having given yield stresses at given temperatures, characterized in that said method comprises the following steps: - preparing a blank (1; 18; 33) having two ends, made up of said metal material of the hollow part (17; 21; 46), and at least one sacrificial mandrel (2; 19; 34, 35) made of a material that, at all temperatures at which the various simultaneous deformations of the blank (1; 18; 33) and the sacrificial mandrel (2; 19; 34, 35), will take place, has a yield stress in the range from -30% to +20% of the yield stress of the material of the blank (1; 18; 33) at said temperatures, preferably in the range from -15% to +10%, ideally in the range from - 5% to +3%; - applying a punch on at least one of the ends of said blank (1; 18; 33) in order to produce the expansion of at least a portion of said blank (1; 18; 33) and to create at least one internal space (12; 20; 37) inside said blank (1; 18; 33); - inserting a sacrificial mandrel (2; 19; 34; 35) in said one internal space (12; 20; 36, 37) of the blank (1; 18; 33); - crimping said sacrificial mandrel(s) (2; 19; 34, 35) in said blank (1; 18; 33); - producing, by co-forging, a simultaneous deformation of said blank (1; 18; 33) and said at least one sacrificial mandrel (2; 19; 34, 35), with a homothetic ratio K; - optionally producing at least one other additional simultaneous deformation of said blank (1; 18; 33) and said at least one sacrificial mandrel (2; 19; 34, 35); - and performing a machining in order to remove the at least one sacrificial mandrel (2; 19; 34, 35) and impart its final configuration to the internal space (12; 20; 37) of the part (17; 21; 46). - preparing a blank (1; 18; 33) having two ends, made up of said metal material of the hollow part (17; 21; 46), and at least one sacrificial mandrel (2; 19; 34, 35) made of a material that, at all temperatures at which the various simultaneous deformations of the blank (1; 18; 33) and the sacrificial mandrel (2; 19; 34, 35), will take place, has a yield stress in the range from -30% to +20% of the yield stress of the material of the blank (1; 18; 33) at said temperatures, preferably in the range from -15% to +10%, ideally in the range from - 5% to +3%; - applying a punch on at least one of the ends of said blank (1; 18; 33) in order to produce the expansion of at least a portion of said blank (1; 18; 33) and to create at least one internal space (12; 20; 37) inside said blank (1; 18; 33); - inserting a sacrificial mandrel (2; 19; 34; 35) in said one internal space (12; 20; 36, 37) of the blank (1; 18; 33); - crimping said sacrificial mandrel(s) (2; 19; 34, 35) in said blank (1; 18; 33); - producing, by co-forging, a simultaneous deformation of said blank (1; 18; 33) and said at least one sacrificial mandrel (2; 19; 34, 35), with a homothetic ratio K; - optionally producing at least one other additional simultaneous deformation of said blank (1; 18; 33) and said at least one sacrificial mandrel (2; 19; 34, 35); - and performing a machining in order to remove the at least one sacrificial mandrel (2; 19; 34, 35) and impart its final configuration to the internal space (12; 20; 37) of the part (17; 21; 46). <EOS>