12-19-2018, 08:40 PM
The actual crown of a barrel is where the rifling exits the barrel not the face of the muzzle. If the actual crown is unevenly cut or has nicks or worn places caused most often my improper use of a cleaning rod it will cause accuracy problems. This is what happens. When the bullet is being pushed down the bore by the gas if the crown is uneven some of the gas will blow by the bullet base on one side before the base of the bullet leaves the other part of the bore and thus cause the bullet to yaw ever so slightly and cause inaccuracy. The base of the bullet needs to leave the bore squarely. I have fix the crown on a number of old military or abused rifles by simply using a round head brass screw chucked in a drill with some valve grinding compound applied. Run the drill slow and place the round head screw with the compound applied to the muzzle and it will center up over the bore and cut the crown square. This turns pattern shooters into group shooters most of the time.