Heat in metal travels to edges, thats the reason for fins on an air cooled engine, not just to increase cooling surface. Anyway, I don't think that flutes stiffen so much (although they do act as stiffeners) as create heat sinks that more rapidly dissipate heat, least so I think, I'm prolly wrong. I have noticed this over the years, without exception octagon barrels shoot better than round barrels of the same size, even though the round has more material and should be stiffer. My Dad and I concluded that heat dissipation was the reason, and the edges of the octagon allowed this. I'm sure that this is not the whole story, as bench shooters go for the largest round barrel they can use, the idea being the bigger the barrel (more material), the more heat it takes to heat it up, the more shots you can get through a "cool" barrel, down side is of course the longer it will take to cool.
I wonder if anyone has ever played with a barrel that has cooling rings the lengh of the barrel, much like an air cooled cylinder. Would look very sci-fi but it should be quite efficient, far more so than flutes.
