Peter, yes I am assuming that, and would hope that they are. If they are not, then this would be useless. But, I also think that in drawings of good barrel wall thickness, a greater/lesser reading that is close to the one before or after would show this.
RWG, the barrel is resting on only 2 points on the rod, one 4 3/4" from left hand stop and the other at close to 24" from stop on left. This way it is away from the chamber and forcing cone and on the 24" is away from the start of the choke area.
When the rod is placed in the left and right pillars, I zero the left side and then the right side, and will check the other two balls as well. Once the barrel is placed on the rod, the dial needle is already on the left zero point, I then move it all the way to the right and check it again for zero. Sometimes the sag is .001-.0015.
