An automatic injection device (100) including a generally cylindrical syringe body having an opening, an outlet and an inner cylindrical surface adapted to contain an injectable liquid to be injected at an injection site via the outlet； a piston disposed in the cylindrical syringe body； a driving assembly (130), including an elongate plunger element (3170) having a forward end adapted to be axially inserted into the generally cylindrical syringe body and an at least partial forward sealing element mounted (3176) onto the elongate plunger element adjacent the forward end for creating an at least temporary slidable seal between the elongate plunger element and the inner cylindrical surface, whereby axial insertion of the elongate plunger element and the forward sealing element into the generally cylindrical syringe body creates friction between the forward sealing element and the inner cylindrical surface and also creates an at least temporary air spring between the forward sealing element and the piston, wherein the friction and the air spring dampen motion of the elongate plunger element.
