thereby enhances function and increases working live it is possible within the scope of the invention to make it possible to regulate this resilience by for example dimensioning a confined volume and a throttle in the conduit supplying hydraulic medium fig3 shows a variant with a distribution valve wherein a chamber 13 u2032 is pressurized with a variable pressure through a variable pressure source 30 against the action of a spring 28 by supplying pressure to this chamber 13 u2032 the valve end wall will thus be adjusted such that the higher the pressure the longer the valve end wall 10 u2032 will be set in the direction towards the second valve end wall 11 u2032 this gives in certain particular operational cases a possibility to regulate the end position of the valve body and thereby the operation of the rock drilling machine in this case u201c abutment u201d shall be interpreted such that the pressure is so high that the spring reaches the bottom wherein a u201c fixed u201d abutment is obtained for lower pressures said adjustability is thus obtained the channels of the distribution valve are not shown in fig3 for the sake of clarity channels for pressurized hydraulic.