Ian
Notorious member
This is a .30-caliber barrel for which the standard thread is 5/8 X 24, but with a medium sporter profile the muzzle diameter is .633". That means there isn't enough barrel diameter to form an adequate shoulder for the muzzle device. That leaves two options: Threading to a smaller standard size, or indexing off of the muzzle face inside the brake. I chose the former and one option is 14 X 1.0 mm, a standard for the AK-47.
Step one is indicate the barreled action true to the bore center through the headstock. I use a gague pin turned to a slip fit in the muzzle (an old bolt in this case).
The other end is more tricky, I usually indicate off of the outside of the barrel to get close and then use a wire clamped to a fixture to reach up inside the action and indicate wobble inside the chamber.
This is the outboard spider I made just for this sort of thing. Barrel is protected by an aluminum sleeve here and by a large copper wire bent into a ring and held in the notches of the chuck jaws. The wire ring in the jaws eases stress on the barrel as it only bears on one point rather than the whole length of the chuck jaws.
Step one is indicate the barreled action true to the bore center through the headstock. I use a gague pin turned to a slip fit in the muzzle (an old bolt in this case).
The other end is more tricky, I usually indicate off of the outside of the barrel to get close and then use a wire clamped to a fixture to reach up inside the action and indicate wobble inside the chamber.
This is the outboard spider I made just for this sort of thing. Barrel is protected by an aluminum sleeve here and by a large copper wire bent into a ring and held in the notches of the chuck jaws. The wire ring in the jaws eases stress on the barrel as it only bears on one point rather than the whole length of the chuck jaws.