Actually, barrel length plays into barrel harmonics, and that relates to accuracy. However, knowing this does not help you select the best length. It's a cut/crown/test situation. Barrel harmonics is one of the reasons a bull barrel is generally more accurate that a light whippy sporter barrel. It's also the reason the Browning BOSS system works. Adjustments to the BOSS move a mass along a length adjustment, tuning the barrel harmonic vibrations.