Data from: How many shots are enough? Optimizing precision measurements when testing lead-free ammunition

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.