For top accuracy you want a close match between bore and bullet diameter, as well as uniformity in the bore and grooves from end to end.

Just as there are different twist rates, there are different types of rifling. Over the centuries, different types have been tried, but the simple land-and-groove style has proven most practical. Today, four- and six-groove barrels are the most popular.

The rifling itself is formed by four common methods. The oldest (and the slowest) is the use of a single steel scraper attached to a long rod to cut each groove individually. The broaching system used by some European manufacturers utilizes a series of cutters that cut all the grooves at once.

In the button process, a short carbide slug with its surface containing a reversed version of the rifling is pulled or pushed through the barrel and the rifling is actually ironed into the bore. In the hammer-forging process, a tungsten-carbide mandrel wearing the rifling in reverse is placed inside the barrel and a very large (and extremely noisy) machine containing multiple hammers capable of delivering tremendous force with each blow pound the barrel into shape both inside and out.

Most shops and companies offer only one type of rifling but there are exceptions. The famous Mark V rifle sold by Weatherby has a button-rifled barrel while the barrel of the Vanguard from the same company is hammer-forged. The barrel of the Remington Model 700 is hammer-forged, but the 40-X target rifle from Remington's custom shop wears a button-rifled barrel.

Savage barrels are button-rifled while Sako barrels are hammer-forged. As barrels made by some of the smaller shops go, those from Shilen, Lilja, Schneider and Hart are button-rifled while Krieger offers both button-rifled and cut-rifled barrels.

I prefer button-rifled barrels because I have had such good luck with them through the years, but I'm quick to admit that the rifling in some of the most accurate barrels in the world is formed by other methods.

The quality of a rifle barrel is dependent, not on the type of rifling it has, but rather on the quality of the steel used, the condition of the tools used to manufacture it and the skill of the person who is operating the machinery