The barrel breach ends should be a sliding fit (metal to metal contact) but not an interference fit that hampers opening and closing. There should be a "couple" of thousandths clearance between the barrel flats and the action bar flats (AKA water table). This allows the bars to flex ever so slightly under the asymetrical loads on the faces and the hinge pin and/or jointing circle. If there is no clearance, the flex will knock the action off-face in short order; the bars are going to flex.