Data from: How many shots are enough? Optimizing precision measurements when testing lead-free ammunition
Data files
Mar 30, 2026 version files 50.38 KB
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Precision_030526.xlsx
32.30 KB
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Precision_Final.R
13.60 KB
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README.md
4.47 KB
Abstract
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.
Dataset DOI: 10.5061/dryad.bg79cnpr8
Description of the data and file structure
These data consist of x–y coordinates of rifle bullet impacts used to evaluate how sample size and grouping design influence estimates of ammunition precision. The dataset includes shot-location data from 37 rifle–ammunition combinations fired under typical field testing conditions. For each combination, shooters fired multiple shots at paper targets, and the horizontal and vertical distance of each impact from the point of aim was recorded. These coordinates were used to calculate precision metrics (mean radius and extreme spread) and to conduct simulations examining how estimates change with increasing group size. Bootstrap analyses were also used to compare three 5-shot groups (3×5) and five 3-shot groups (5×3) and evaluate how each design influences precision estimates. The shot-location data were originally collected during a study comparing factory and handloaded lead-free ammunition (McTee et al. 2025, Wildlife Society Bulletin e1570).
Files and variables
File: Precision_030526.xlsx
Description: Excel workbook containing rifle precision data used to evaluate how sample size and grouping design influence estimates of rifle precision.
The workbook contains two sheets:
1. Precision
Primary dataset containing individual shot coordinates for each rifle–ammunition combination.
Each row represents a single bullet impact recorded on a target.
Variables
- Shooter_ID
Identifier for the rifle/shooter combination used during testing. - cartridge
Cartridge used during testing. - Bullet
The bullet type and mass used in the ammunition were tested. All lead-free. - Shot Group
An integer identifying the group number in which the shot was fired. - x_inch
Horizontal distance of the bullet impact from the point of aim (inches). - y_inch
Vertical distance of the bullet impact from the point of aim (inches).
Shot coordinates were recorded relative to the point of aim and used to calculate precision metrics, including mean radius and extreme spread.
These coordinates were used in resampling simulations and bootstrap analyses to evaluate how group size and grouping structure influence precision estimates.
2. Rifle info
Supplementary sheet describing rifles and ammunition used during testing.
This sheet includes descriptive information about:
- rifles
- cartridges
- ammunition types used in each comparison
These variables provide context for the rifle–ammunition combinations used in the precision dataset, but are not required to run the simulation script.
Rifle Cartridge: type of ammunition (caliber) the rifle is chambered for
Barrel Twist (in): tells how fast the rifling spins the bullet
Rifle Make/Model- brand and model of the rifle
Barrel Length (in): Length of the barrel in inches
Estimated Value: Approximate price of the rifle setup
Scope Make/Model: The optical sight mounted on the rifle
Handloaded Bullet:a specific bullet used in handloaded ammo
Comparison Ammunition: Factory-produced ammo used to compare performance vs the handload
Code/software
Precision_Final.R: The R script included evaluates how sample size and grouping design influence estimates of rifle precision. The analyses use precision data from 37 rifle–ammunition combinations collected under typical field testing. The script calculates mean radius and extreme spread using resampling simulations to examine how these metrics change with increasing group size and to estimate points of diminishing returns with nonlinear asymptotic models. A bootstrap analysis compares two common precision testing designs (three 5-shot groups versus five 3-shot groups) and quantifies how each design underestimates precision relative to the full 15-shot reference value. The script also produces figures illustrating precision metrics, sample-size effects, and bias associated with alternative grouping strategies.
Data are stored in Microsoft Excel (.xlsx) and were prepared with version 16.107. Graphics and analyses were conducted in Program R (version 4.5.0) using the RStudio platform (version 2025.05.0+496). Analyses were run using the R script included with this submission (Precision_Final.R).