Hand-lapping is accomplished via a lead slug coated with a fine-grade abrasive that's pushed and pulled through the bore to smooth it.

Aftermarket barrels are manufactured in several grades, but to keep it simple I'll divide them into three groups. The Utility grade is for the rifleman who wants to build a good shooter but is satisfied with less than tackhole accuracy. Several shops offer this grade of barrel and the two that come to mind are McGowen and E.R. Shaw.

Other shops offer Match Grade along with what I refer to as Benchrest Grade barrels, with Shilen being a good example.

As far as accuracy goes, the primary differences between the three grades of barrels are how close bore and groove dimensional tolerances are held during their manufacture and how smooth their bores are. Benchrest Grade barrels (and some Match Grade barrels) are bored and rifled slightly undersize and then a lead lap coated with a mild abrasive is used to arrive at the finished diameters.

RECOMMENDED* RIFLING TWIST RATES .224 caliber 1:7 -- heavier than 80 gr. 1:8 -- up to 80 gr. 1:9 -- up to 70 gr. 1:12 -- up to 63 gr. 1:14 -- up to 55 gr. 1:15 -- up to 55 gr. at 4,100 fps or faster 1:16 -- up to 45 gr. or up to 55 gr. at 4,300 fps or faster .243 caliber 1:8 -- VLD bullets over 100 gr. 1:10 -- up to 100 gr. and VLD bullets lighter than 100 gr. 1:12 -- up to 85 gr. 1:13 -- up to 75 gr. 1:12 -- up to 70 gr. .257 caliber 1:9 -- up to 120 gr. 1:10 -- up to 100 gr. 1:12 -- up to 90 gr. 1:13 -- up to 80 gr. 1:14 -- up to 70 gr. 7mm caliber 1:8 -- up to 180-gr. VLD 1:9 -- heavier than 140 gr. 1:10 -- up to 140 gr. .30 caliber 1:8 -- heavier than 220 gr. 1:10 -- up to 220 gr. 1:12 -- up to 170 gr. 1:14 -- up to 168 gr. 1:15 -- up to 150 gr. 1:17 -- up to 125 gr. *Partial listing of recommendations for pointed bullets from Shilen Rifles, Inc. Abbreviation: VLD, very low drag

In addition to reducing any diameter variations left from the boring and rifling processes, lapping also removes bullet jacket-grabbing tool marks that run across the lands and grooves. The fellows who hand-lap rifle barrels have arms like Popeye and usually finish no more than a half-dozen barrels during a hard day's work. In large part, this explains the higher cost of a super-accurate barrel.

The bore and groove diameter of a Shilen Match Grade barrel will be no more than .0005 inch larger or smaller than is standard for a particular bullet diameter and bore, and groove diameter will vary no more than .0003 inch from one end of the barrel to the other.

Moving up a bit in precision, bore and groove diameter of a Benchrest Grade barrel from Shilen will be within .0003 inch of bullet diameter standard and uniformity will be within .0001 inch from chamber to muzzle.

To put those tolerances into perspective, a single page of the wonderful publication you now hold in your hands is .002 inch thick or 20 times greater than the end-to-end bore and groove diameter variation of a Benchrest Grade barrel. Several other shops offer Benchrest Grade barrels--Lilja, Schneider, Hart, Pac-Nor and Krieger to name a few.

So which grade do you choose? Thousands of hunters and shooters are quite satisfied with Utility Grade barrels, which is what the majority of factory-built rifles wear. A barrel of this grade capable of delivering accuracy as good as an aftermarket Match Grade barrel does occasionally come along, but only rarely is one as accurate as a Benchrest Grade barrel.

Serious benchrest competitors always use the most accurate barrels available simply because in order for a rifle to win at that game it must be capable of consistently shooting five bullets inside .200 inch at 100 yards.

I usually stick with Benchrest Grade regardless of what the rifle will be used for. It is usually not all that much more expensive than Match Grade, and even though I may not actually need its accuracy in the field, it gives me confidence and the more confident I am in a rifle the more accurately I shoot it.