A buffer with a self-adjustable stopper including a buffer head, a base having a guide profile, and a central body having a groove cooperating with the profile, the central body being mounted on the base by a translation movement, in a first direction (X) in a plane of movement, the central body at least partially receiving the buffer head. The buffer head includes a locking member inserted into the central body in a second direction (Y) and blocks in a third direction (Z) the buffer head in the central body and blocking in the first direction the central body on the base. The locking element and the buffer head include, respectively, at least one thrust ramp and at least one housing adapted to receive said at least one ramp adapted to, when the locking member is translationally actuated, produce a camming effect and to allow raising of the buffer head.