Barrel-Indexing Rimfire Action — Rotate Barrel Around Bore Axis

The late Bill Myers was recognized as one of greatest rimfire smiths who ever lived. Myers crafted many match-winning, record-setting rimfire benchrest rigs. Here we feature one of Bill’s most interesting creations — a clamping action that allows a rimfire barrel to be indexed (rotated) around the bore axis.

Bill was a creative thinker, and his own exhaustive testing has convinced him that barrel indexing can enhance accuracy in rimfire benchrest guns. Myers did acknowledge that, particularly with a very good barrel, the advantages of indexing may be subtle, and extensive testing may be required. Nonetheless, Myers believed that indexing could improve rimfire accuracy.

Indexing with the Myers’ Clamping Action
To index the barrel, Myers simply loosens the three clamping-bolts and rotates the barrel in the action. Because there is no thread to pull the barrel in or out, the headspace stays the same no matter how much the barrel is rotated. In other words you can rotate the barrel to any position on the clockface and the headspace remains unchanged.

The Challenge of Barrel Indexing
With a conventional barrel installation, employing a shoulder with a threaded tenon, it is difficult to index the barrel. Even with a cone breech (photo right) that eliminates the problem of extractor cuts, you’d have to use shims to alter the barrel index position, or otherwise re-set the shoulder each time you screwed the barrel in further.

Clamping Action Allows Barrel to Be Rotated to Any Position
Bill has come up with a masterful solution to barrel indexing. He designed and built his own prototype custom action that clamps the barrel rather than holding it with threads. The front section of the action is sliced lengthways, and then clamped down with three bolts. A special bushing (the gold-color piece in photos) fits between the barrel and the action. By using bushings of different inside diameters, Bill can fit any barrel up to an inch or so diameter, so long as it has a straight contour at the breech end. To mount the barrel, Bill simply places the fitted bushing over the barrel end-shank, then slips the “sleeved” barrel into the front end of the action. Tighten three bolts, and the barrel is secure.

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Tags: barrel rotation, Bill Myers, Index, Indexing action, Rimfire