Assessing the long-range performance of copper bullets on North American elk (Cervus canadensis)

Context Recent advancements in firearm technology have enabled hunters to take increasingly longer shots at animals (i.e. ≥300 m). The performance of copper bullets at these distances remains largely anecdotal, despite growing use to reduce lead exposure in scavengers and game meat. Aims We evaluated whether copper bullets perform effectively during long-range hunting and identified possible factors influencing bullet performance and animal recovery. Methods At MPG Ranch in western Montana, USA, we collected field data from hunters required to use lead-free ammunition. We recorded shot distance, shot placement, copper bullet selection, estimated impact energy, and recovery status of elk (Cervus canadensis). We also measured bullet expansion and weight retention for recovered bullets. Key results The average shot distance for recovered elk (n = 111) was 305 m, whereas that for unrecovered elk (n = 13) averaged 391 m (t = 3.37, P = 0.002). Proportional odds logistic regression showed that the number of shots impacting elk was predicted by flight distance and whether the bullet was designed to fragment; however, flight distance was not predicted by impact energy or bullet design. Recovered bullets retained 97.2% of their mass (n = 7), and their expansion ratios, calculated as the expanded frontal area divided by the original, ranged from 3.1 to 4.1. Conclusions Copper bullets can be effective at long range when used by skilled shooters, with recovery rates being similar to or exceeding those reported in prior studies where ammunition type was likely a mix of lead and lead-free projectiles. Implications Our findings support the suitability of copper bullets for long-range hunting and suggest that hunter skill and shot distance, rather than bullet material alone, are key factors in animal recovery.