Lapping Bolt-rifle Locking Lugs

Lapping Bolt-rifle Locking Lugs

- Gil Sengel

The search for ever-better accuracy from our rifles is never ending. Not surprisingly, virtually all accuracy-enhancing developments have come from individual shooters. Among these, however, are some that sound good but don’t always work out as expected.

A good example is resizing only the case neck when handloading for ordinary hunting rifles. Some astonishing claims were made for this idea in the 1950s and 60s. Having grown up during that time, I saw my dad and his shooting buddies try the idea in everything from wildcat .22 centerfires to .375 H&H Magnums, from custom rifles to factory Remington Model 721/722s. If there was any improvement at all, it was nothing like that reported by certain gun writers.

Another example of something that sounds good is lapping an action’s locking surfaces. Supposedly an aid to accuracy, it is always done when “blueprinting” an action and now more commonly by those rebarreling rifles that are expected to be accurate – like well under a minute of angle. But does it really add anything?

The work is actually quite simple, yet there are a number of pitfalls to avoid. First is to realize limitations. While a very few exceptions come to mind, lapping locking surfaces is generally applicable only to turn-bolt actions that are to be rebarreled. These must have locking surfaces integral with the receiver, not machined into the rear of the barrel or in an extension permanently attached to the rear of the barrel. This is because lapping can only be done before a new barrel is installed, or with the old barrel removed.

Yes, I know there have been articles and even gunsmithing books that recommend daubing abrasive onto locking surfaces of complete rifles. The bolt is then opened and closed, using pressure of the mainspring on the sear of the cocked action to hold the surfaces in contact.