What you said about a doll's head NOT being able to prevent action from moving backward, away from barrels is not true! Should an action attempt to break or stretch, the doll's head, if tight fitting, should prevent that from happening, especially if it has bite through doll's head, same thing is done by Greener crossbolt. All actions, upon being fired, will spring so slightly, very briefly, to the rear, but will spring back (this is normal for even modern steel alloy used in action building). If stress, upon firing, is too great, the metal will fail and not spring back, but will stretch or break, and a doll's head attempts to help that from happening. Best, Jack