The concept of barrel indexing has been around for a number of years as a method of improving accuracy in rifles. The indexing process is currently getting a lot of attention in rim-fire small bore rifles with controversy about the benefits. Our findings are that every index test we have done has resulted in an improvement. Some improve more than others but in no case has there been a reduction in performance.
The majority of barrels, including custom made barrels, have a slight curve in the bore. This curve is generally not considered a defect but normal to the barrel making process. Barrel Indexing is the process of aligning the curve of the barrel to the vertical axis when mounted in the action. In most cases the bore curve will be indexed with the curve down orientation as this position usually provides the best accuracy. The orientation position could vary with a particular barrel. With the barrel indexed in the vertical position the forces acting on the barrel by the bullet during its travel in the horizontal axis are minimized. With the use of a tuner the vertical component of the forces can be more easily modified improving repeatable accuracy performance. Barrel tuners are commonly used on rim-fire bench rest rifles, and may mask the benefits of barrel indexing. An indexed barrel used with a tuning device can improve the competitive features of an already competent rifle. The beneficial affect of an indexed barrel should not be ignored.
The preparation process for live fire indexing a barrel begins with a measurement of the critical areas of the barreled action. The outside diameter of the barrel is confirmed and the barrel centerline is established. The outside diameter profile of the barrel is checked for any run out and noted. The bore of the barrel is examined for concentricity to the outside profile at both the muzzle and the chamber ends of the barrel. An off axis condition needs to be isolated and understood before live fire testing begins.
Live fire testing will be done with the barrel mounted just ahead of the receiver in a very stable “V” block fixture. Five rounds will be fired in each of eight positions covering 360 degrees of rotation. The “X” axis will be accurately moved between index rotations so the vertical dispersion can be evaluated. The five shot group will be evaluated at each position relative to size and shape with any vertical or horizontal tendencies noted. After the index position is determined it will be further examined with 25 rounds fired at that index. Size and shape will be evaluated to confirm the index.
We offer barrel indexing as part of our rim fire barrel fitting process. We can also index your barrel only using a slave receiver and mark it for fitting by others. Call for current indexing and fitting prices.
Indexing a barrel blank will require cutting a tenon 1 inch long for a slave receiver that will be removed afterward. The cost for indexing a barrel blank is $75.00. Doing multiple barrels at the same time will be discounted.
Indexing and marking a complete barreled action is $45.00. The cost of refitting the barrel to a new index position is dependent on the type of barrel juncture.
Contact us for more information.