A rock drilling machine with a first control means (21, 22) within a second piston (6) and acting on a first piston (13) such that it counteracts displacement of the relative positions of a first and a second control device at the moment of contact of the second piston onto the drill rod or onto a part (9) connected to this. Furthermore, a rock drill rig comprising such a rock drilling machine and a method for counteracting the said displacement. Significant improvements in reproducibility for impact mechanism stability over long manufacturing series are achieved through the invention. In the same way, the lifetime of rock drilling devices manufactured according to the invention is extended through the impact mechanism acting in a more stable manner despite wear of component parts. It is furthermore possible to dimension for higher rates of impact without risking the impact mechanism stability.