With the bolt pulled back, apply the safety. On the barrel jacket, left side, directly under the rear sight is a latch. Press hard and twist the receiver down.
Rotate the receiver 180 degrees. The receiver rotates down, because when mounted in the Lafette tripod, it is fixed, meaning that the barrel needs to be rotated up.
Same view from the front.
Using the hook in the end of a belt starting tab, pull the barrel out. After firing 50 rounds, the barrel is hot enough to burn. Care must be taken.
Close up
Right front view
Left front view. Replace with a new barrel and rotate the receiver back with firm pressure to ensure that it locks back in place.