In one aspect of the invention, a method of reducing intersymbol interference on a signal line is disclosed. A number of fine precipitates of 1 m or less in particle size is controlled at a ratio not more than 6105mm2. A movable gun mount is mounted to the frame front adjacent the window mounted therein and has a gun having a barrel removably mounted thereto with the barrel extending through an opening in the front of the flexible ballistic shield material which allows a person to move the gunfire shield while protecting the occupant from gunfire and simultaneously operate the gun from thereinside. A substrate is mounted in the cavity. An endless elastic member is retained by one side wall of the receptacle.