Handloader|February - March 2022
Mike Venturino

Slugging barrels is a process by which an oversized, soft (pure) piece of lead is driven through a rifle or handgun barrel. The idea is to determine a rifled barrel’s diameter across its grooves. This is so cast bullets can be purchased or home-sized to fit, preferably at or about .001 inch over groove diameter.

There are two questions involved. One is, “How to slug barrels?” The second is, “When to slug barrels?” On the surface, slugging barrels seems easy. Simply drive an oversized soft piece of lead down the rifle or handgun barrel. Actually, this should be done with some finesse lest a barrel is damaged along the way. We’ll return to that process shortly.

Upon purchasing my very first centerfire revolver, an S&W K38, I asked the fellows at my local gun club whether I should slug its barrel. After all, my brand new Lyman manual gave instructions on how to go about that. Those older gents laughed and in essence said, “Don’t worry about it. Smith & Wesson’s barrels are all the same per caliber. Besides, they have an odd number of grooves (five) so it is difficult to measure them unless you have a V-block and a solid grasp of mathematics.” I had neither, so for 55 years I’ve shot all smokeless-era S&Ws with nominal cast bullet diameters as in .358 inch for .38/.357 and .430 inch for .44 Special/.44 Magnum. With good quality hand loads, accuracy has always been superb.

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