The grip safety would also have come in handy on a rail shooting boat where the gunner sits in the bow with the butt of his gun resting on the deck of the boat and his left hand on the barrels. The hunter's buddy or hired hand poles the rail boat through the flooded marsh. When the rail flush, there isn't much time for a gun that is not on full cock! I have done this in the wild rice marshes in South Jersey not far from Philadelphia. I would not be surprised if rail boats have been poled through those marshes ever since the flinters and later percussion guns were in use.