Let's take as an example a Winchester 1886 chambered for a relatively familiar cartridge, the .40-65. It is representative because it exhibits most of the problems one is likely to encounter. In the late 1800s, scores of cartridges were developed by gunmakers, and many of their designations overlapped. The same cartridge chambered by two companies might be given different names; other times different cartridges were given the same name. The .40-65 Winchester is exactly the same cartridge as the .40-60 Marlin, whereas the .40-60 Winchester is completely different.

Three slugs from a .38-55. The slug on the left is unused. The center slug has been driven through the bore but was too small to achieve its purpose. The slug on the right was large enough to completely take the bore shape, as shown by the lead that flowed back as it was swaged down.

After determining the chambering, the next thing you need to know is the actual bore diameter of the rifle. The .40s were notorious for a lack of standardization even among rifles from the same manufacturer. A nominal .40 might be anywhere from .403 to .410. The later .405 Winchester was .412, made that way to prevent owners of .40-70 Straight Sharps rifles from chambering the higher-pressure .405. The cases were otherwise almost identical. Similarly, rifles for the ever-popular .38-55 display a wide range of diameters above and below the nominal .375.

Assuming that even minimal accuracy is important to you, knowing the bore diameter is critical because it dictates bullet, mold and loading-die dimensions. Shooting a .406-diameter bullet through a .410-diameter bore usually results in key-holing bullets and a group that resembles a shotshell pattern of oblong holes. Good luck.

Slugging a bore is considerably easier than it used to be because MidwayUSA markets Slug Your Barrel kits made by Meister Bullets. These consist of a selection of smooth lead cylinders in ascending diameters. In the case of the .40s, they range from .398 to .414 inch; you pick one that is slightly larger than your bore and tap it through using some hardwood dowels. The resulting slug allows you to measure both bore and groove diameter.

That sure beats my old method of finding a wadcutter bullet and either squeezing it in a vise or rolling it to get something approximating the right diameter, then hammering it through.

The Meister Bullets Slug Your Bore kit makes slugging a barrel so easy that it is hard to resist doing it with every rifle you own. The resulting slug, which is a perfect reverse image of the bore, can be kept for future reference. Groove diameter is measured with a micrometer, bore diameter with a caliper.

Once you know the bore diameter, you can start assembling the necessary tools and components. If a person is willing to plunge into the world of bullet casting and swaging, the sky's the limit. For our purposes, though, we'll assume you are a knowledgeable handloader who just wants to shoot the rifle, either at paper or game, and is not about to embark on a career of 1,000-yard matches.

In that case, you will need jacketed bullets that are bore diameter or cast bullets one or two thousandths of an inch larger. For a bore that is .408, for example, cast bullets of .409 or .410 should work pretty well.

If you have a bore that is a really weird size, some small bullet casters will produce special bullets, provided you buy enough of them. As well, if you can find a mold you like, many will produce bullets from your mold, saving you the trouble of learning to cast bullets (an activity that can, and has, filled entire books).