Growing concern about lead exposure in scavenging wildlife and the consumers of game meat has increased interest in evaluating the performance of lead‐free rifle ammunition. Testing both accuracy and precision helps ensure reliable shot placement while reducing the risk of non‐fatal woundings. However, precision testing methods vary across studies, sometimes leading to contrasting interpretations of ammunition performance. Using shooting range data from 37 rifle‐ammunition combinations tested under typical shooter‐operated conditions, we evaluated how precision estimates based on extreme spread and mean radius change with increasing sample size and identified points of diminishing returns. We also compared whether three 5‐shot groups (3 × 5) or five 3‐shot groups (5 × 3) produce more reliable precision estimates. Mean radius stabilized at relatively small group sizes (n = 9), whereas extreme spread showed weaker evidence of stabilization. Additionally, 5 × 3 groups underestimated 15‐shot reference values more than 3 × 5 groups. Based on these results, we outline best practices for evaluating ammunition precision, including using at least 10 shot groups when feasible, reporting both mean radius and extreme spread, favoring 3 × 5 designs over 5 × 3 designs, and testing across multiple rifles, while reporting barrel twist rate and length, bullet mass and length, and muzzle velocity.
McTee et al. (Thu,) studied this question.