A mounting device for a telescopic sight of a firearm, comprising: ▪ a mounting base having a first longitudinal side, a second longitudinal side, a longitudinal axis enclosed between the first longitudinal side and the second longitudinal side, and a support for holding the telescopic sight, ▪ a front and a rear insertion pin (12, 14), ▪ at least one movable clamping pin, and ▪ actuating means for each of the at least one movable clamping pin, ▪ wherein the insertion pins (12, 14) are arranged laterally on the first longitudinal side of the mounting base along the longitudinal axis for engagement in first recesses of a barrel of the firearm, ▪ wherein the at least one movable clamping pin is arranged for selective engagement in a corresponding second recess of the barrel on the second longitudinal side and is movable transversely to the longitudinal axis, ▪ wherein the respective actuating means comprises an elongate adjusting member which is coupled to an actuator element, extends through an aperture in the mounting base and has a first end disposed on the first longitudinal side and a second end disposed on the second longitudinal side, and ▪ wherein the second end of the adjusting member is fixedly connected to the at least one clamping pin and is preferably integrally formed therewith, ▪ characterised in that the actuating means has a base body with a first curved surface which is directed towards the adjusting member and at least regionally contacts a second curved surface formed on the mounting base, the first curved surface and the second curved surface being formed to slide rotationally on each other about an axis formed by the adjusting member and, upon rotational sliding, linearly displace the base body and thus the adjusting member along its axis, whereby the actuating means is adapted to move the adjusting member along its axis by rotation exerted via the actuator element and thereby pull the associated clamping pin towards the first longitudinal side. ▪ a mounting base having a first longitudinal side, a second longitudinal side, a longitudinal axis enclosed between the first longitudinal side and the second longitudinal side, and a support for holding the telescopic sight, ▪ a front and a rear insertion pin (12, 14), ▪ at least one movable clamping pin, and ▪ actuating means for each of the at least one movable clamping pin, ▪ wherein the insertion pins (12, 14) are arranged laterally on the first longitudinal side of the mounting base along the longitudinal axis for engagement in first recesses of a barrel of the firearm, ▪ wherein the at least one movable clamping pin is arranged for selective engagement in a corresponding second recess of the barrel on the second longitudinal side and is movable transversely to the longitudinal axis, ▪ wherein the respective actuating means comprises an elongate adjusting member which is coupled to an actuator element, extends through an aperture in the mounting base and has a first end disposed on the first longitudinal side and a second end disposed on the second longitudinal side, and ▪ wherein the second end of the adjusting member is fixedly connected to the at least one clamping pin and is preferably integrally formed therewith, ▪ characterised in that the actuating means has a base body with a first curved surface which is directed towards the adjusting member and at least regionally contacts a second curved surface formed on the mounting base, the first curved surface and the second curved surface being formed to slide rotationally on each other about an axis formed by the adjusting member and, upon rotational sliding, linearly displace the base body and thus the adjusting member along its axis, whereby the actuating means is adapted to move the adjusting member along its axis by rotation exerted via the actuator element and thereby pull the associated clamping pin towards the first longitudinal side.