Smallbore rifle and pistol matches can be lost by fractions of a point. At the highest levels of competition, any advantage can mean winning or losing. Olympic and world prone rifle champion Matt Emmons used the Nielson Brothers Arms .22 rimfire bullet concentricity gauge at the Athens Olympics.

Bullet concentricity is simply the alignment of the axis of the bullet to the axis of the case. Lester Nielson began investigating improved .22 long rifle accuracy in 1994. Teaming up with H-S Precision, Nielson used H-S Precision's shooting tunnel to derive results that indicated that bullet concentricity affected rimfire accuracy, even with match-grade .22 LR bullets.

Nielson found that the groups increased with each thousandth's increment increase in allowable measurement of concentricity. Twenty rounds with a concentricity measurement of 0.000" averaged a 0.24" group size. Twenty rounds with a concentricity measurement of 0.003" averaged a 0.35" group.

We tested a variety of ammunition with the Nielson Bullet Concentricity Gauge and were surprised by the amount of deviation that we found in one box of match ammunition. Eley Tenex displayed the best and most consistent results. In a box of 50, just 10 percent measured 0.003" of run-out and averaged 0.0013". Removing the 10 percent of ammunition that displayed 0.003" of run-out would have improved the average for the remainder of the box to 0.001".

Through testing completed at the Olympic Training Center in Colorado Springs, Colo., Nielson formulated that for every 0.001" error in the concentricity of a bullet, dispersion increases 0.1" at 50 meters. Referring to the sorted ammunition test, 1 to 2 percent of cartridges in a box of match ammunition measured 0.004". If fired, these bullets can increase a group size to as much as 0.77" at 50 meters. Because multiple factors influence a bullet's flight path, this doesn't conclusively improve a shooter's group size. Rather, the Bullet Concentricity Gauge from Nielson Brothers Arms allows the most demanding smallbore competitors to reduce the influence that excessive run-out can have on their scores.