BM,
I am aware of the technque in fitting pistons, but, you know, this interference fit involves IDs and ODs measured in inches, not usually small decimal fractions, so I believe the actual "gain" in bore diameter (if there is one) is so negligible as to be insignificant, regardless of fluting....assuming we are talking about a "warm" barrel? Besides, the process usually involves heating one part and cooling the other part.
One definition od warm might be: able to grasp the barrel without pain. And, I admit, my knowledge of auto mechanics is not any greater than my knowledge of the physical characteristics of rifled barrels, at various temperatures.
Fluting, whether even or odd, I defer. Fluting adding stiffness during recoil, I also defer to our experts. Advantages of fluting, versus disadvantages, I'll sit that one out, as well.
As to actually heating a barrel enough to slightly expand the OD, I believe it may increase the length, as well. Should we have a metallurgist lurking about, perhaps we can learn if the various alloys expand in known, and predictable dimensions?
For instance, I heard, once that the SR71 gains length, in the air at speed, as the skin heats up, and when it lands, and cools off; all the fuel tanks leak badly. Okay, poor example, perhaps?
Does the bore increase in size, unevenly (WHEN WARM) due to fluting, that is the question.
Not only am I of the mind that it doesn't increase enough to actually measure, (or worry about) but I am also skeptical of the suggestion that what expansion "might" exist, is UNeven expansion, because of the flutes. And, which might turn the "warm" barrel into one with a polygonal (and rifled) bore; for lack of a more accurate term.
If the barrel were made of bread dough, and baked in an oven, would the bore size expand, as would the outer diameter? Fortunately, barrels are not made this way, but the bore would be smaller, would it not? It may not have the slightest application, in this discussion, but it does illustrate the thought behind my ignorant statement.
Good hunting. LB