Probably not germane to the op...but I was bluing a barrel yesterday, remembered this topic, and took some very precise (without an electron comparator) EXTERNAL measurements with a Swedish ten thou. mike. Tried to eliminate every variable I could think of, recorded my measurements and re measured after bluing when the temperature stabilized back to the starting test temp. You guessed it...no change. Conclusion? If there was no physical dimensional change, I doubt you could quantify a velocity change given all the variables.
