This disclosure relates to a method and an arrangement for low or non-rotating artillery shells fired from launch weaponry, and which introduces a portion of the barrel pressure built up in the barrel during the launch phase into a chamber arranged in the low or non-rotating artillery shell which is delimited in at least one direction by an element which is movable relative to the rest of the shell when a differential pressure between the chamber and the external environment of the shell is sufficient to move the element. The moveable element may be a protective casing covering fins of the artillery shell.