Here's a closer view. I have cut an inch off the barrel, and refaced the end. I cut from the center out to not push a burr into the bore. This is important for the indicator rod. You will notice aluminum L's between the chuck jaws and barrel. I have finished dialing the barrel in. I start with a .001 indicator, and finish with a .0001 indicator. I indicate in two places on the rod to dial in both ends of the barrel.
Here is the indicator rod with removable bushing. The rods are tapered. You choose a bushing to precisely fit the bore, then slide the rod in until the taper stops it. It is critical there are no burrs on the bore, and the bore is clean. There are several ways to dial in. They all work if you understand the possible shortcomings.
Here is the outboard end of the head stock. The four opposing screws are called a spider. This allows both ends of the barrel to be dialed in. The barrel has an aluminum collet around it to prevent marring, and to aid dialing. The action is temporarily installed to mark the top flute, for brake timing.
Here is a photo of the aluminum L's in the chuck. These allow the barrel to pivot when dialing in, and prevent slipping and marring. The brass tipped screws (they are .22 shells) are in the spider. This makes for a short pivot point, prevents marring, and aids dialing.
This is the brake the customer supplied. I believe it is from Center Shot Rifles. The next steps are to turn the barrel to diameter, thread the barrel, time the brake, recheck our dial in, cut the barrel crown, install the brake, drill the brakes bore hole, double check our bore hole alignment and size, chamfer the edges, cut the taper on the brake, blend the brake, and bead blast. If that isn't a run-on sentence... As you can see, some thoughtful person labeled the top of the brake to keep the gunsmiths world right side up .