It has been 40+ years since my discussion with my Dad, but I seem to remember mention of a star shaped gauge to measure the rifling ID. Rounded points to contact the rifling may have been involved, hence the shape? Gauging to confirm all measurements are in spec would not necessarily give you the most accurate barrel.

On the other hand selecting the straightest barrel in a batch and giving it special treatment might could give you something special as to accuracy.

On a recent thread Chuck found a bolt with a star on it, anyone else find a receiver with such a mark? With the mixing of parts on rebuilds if one rifle had all its parts marked with a star it would be very unlikely they stayed together.