A setting tool for driving fastening element in constructional components includes a setting mechanism having a combustion chamber (111) for generating expanding gases, a piston guide (117) adjoining the combustion chamber (111), a bolt guide (116) adjoining the piston guide (117) in the setting direction (140), and a drive piston (10) displaceable in the piston guide (117). The piston includes a piston head (11) and a piston body (12) connectable along an interface (13) with the piston head (11), the piston head (11) and the piston body (12) having, respectively, in an interface region, at least one stop surface (14) and at least one counter-stop surface (15) formed by surfaces defining essentially complementary tapering regions.