David:

If you are zeroing your gauge while it is resting on the stands, then putting the rod through the barrel and resting it on its stands, does either end of the barrel rest on the stand? Or is the other barrel resting on the bench thereby raising the height of the rod through the barrel? How do you keep two pressure points on the gauge head if the ball is fixed at the breach and muzzle ends? Any flex or sag in the rod?

I am more familiar with the vertical, free standing BWT gauge from Galazan and others of that ilk, then horizontal bar gauges. Russ