Fluting (machining lengthwise grooves into the outer surface of the barrel) increases the surface area of the barrel - thereby allowing increased radiational cooling of the barrel mass. This process also adds to the "stiffness" of the barrel which enhances its accuracy. A third benefit of fluting is that the barrel is lighter after machining removes the steel in those lengthwise grooves. A fluted barrel will last longer, shoot straighter, and is considerably lighter than a standard heavy barrel. The accuracy gains would be most noticeable at longer distances or to the competition shooter, but for only $50 additional for most Bushmaster barrels, many feel that the benefits of fluting are well worth the cost.