Bullet fragmentation study

Lead fragments appear as white flecks in this x-ray of a radiographed sheep from the study.

The intent of the study was to conduct an experiment that would control for bullet caliber and focus on examining the variability of lead fragmentation and deposition associated with distinctly different categories of bullets and firearms used to harvest deer in Minnesota.

We selected bullets based on their advertised performance and consumer availability and found that using bullets with no exposed lead (a copper case completely surrounds the lead core) or copper are two ways to significantly reduce or eliminate lead exposure.

The study was conducted in July 2008 at Carlos Avery Wildlife Management Area. X-Rays and CT scans were taken at the University of Minnesota Small Animal Hospital and lead analysis was completed by the University of Minnesota Veterinary Diagnostic Laboratory.

Methods

Firearms & ammunition

1. A .308 centerfire rifle was used to fire 150 grain bullets with five bullet designs:
   •  Rapid expansion (ballistic tip, soft point)
   •  Controlled expansion (exposed lead core, non-exposed lead core)
   •  Non-lead (copper)
2. A .50 caliber muzzleloader using 100 grains of powder (2 pellets, 50 grain Hodgdon 777) with two different bullet designs:
   •  245 grain 
   •  300 grain 
3. A 12-gauge shotgun firing a one-ounce Foster-style slug
4. Three sheep were shot in the pelvic region using a ballistic tip, soft point and slug to document dispersion of lead in animals hit with a poorly placed shot.

Preparation & analysis

• Seventy-two previously euthanized domestic sheep were used as a surrogate for white-tailed deer.
• Each sheep was propped up in a broadside position and shot in the thoracic cavity at 50 meters. A chronograph was used to record the velocity and bullets were recovered using a box filled with sand behind the target.
• We skinned and gutted each carcass and inserted a carbon fiber tube through the wound channel prior to taking a radiograph on the exit wound side. We also rinsed carcasses of sheep shot with both types of rapid expansion bullets and took a second radiograph to determine the effect washing had on fragment distribution.
• A veterinarian counted the number of fragments and measured the maximum distances the fragments travelled.
• The extent of lead contamination in muscle tissue was determined using techniques similar to other studies published in scientific literature. We collected muscle tissue samples at 2, 10 and 18 inches from the exit wounds. We also measured the diameter of the entry/exit holes and the wound channel length. 

Results

Copper and non-exposed lead core: These bullets averaged nine copper fragments in the animal with an average maximum distance from the wound channel of seven inches. By design, copper bullets leave no lead and the few fragments that were seen on x-ray were less than an inch from the exit wound.  Overall, both of these bullet designs fragmented very little and left no lead.

Ballistic tip (rapid expansion): These bullets had the highest fragmentation rate, with an average of 141 fragments per carcass and an average maximum distance of 11 inches from the wound channel.  In one carcass, a fragment was found 14 inches from the exit wound.

Soft point (rapid expansion): These bullets left an average of 86 fragments at an average maximum distance of 11 inches from the wound channel.  In this research, bonded lead-core bullets (controlled expansion, exposed lead core) performed almost identically to the soft-core bullets and left an average of 82 fragments with an average maximum distance of nine inches from the wound.  

Shotgun slugs: These slugs left an average of 28 fragments at an average maximum distance of five inches from the wound channel.

Muzzleloader: The 245-grain bullet left an average of three fragments while the 300-grain bullet left 34 fragments at average maximum distances of one and six inches, respectively.

Key findings

• Using bullets with no exposed lead (a copper case completely surrounds the lead core) or copper are two ways to significantly reduce or eliminate lead exposure.
• A key take away is that given fragments were found so far from the exit wound, routine trimming likely will not remove all of the fragments and DNR cannot make a recommendation as to how far out trimming should occur. 
• In counting fragments, only about 30 percent were within two inches of the exit wound. The vast majority was dispersed further from the carcass.  In some cases, researchers found low levels of lead as far away as 18 inches from the bullet exit hole.
• The DNR also learned that rinsing a carcass produced mixed results. While rinsing tends to reduce lead around the wound channel it also transports lead away from the wound.
• The research also showed that a shot to the hindquarters of a deer – where heavy bones are found – will result in extensive fragmentation. Fragmentation was so pronounced that a hunter would likely not want to utilize this meat as there would be no way to remove all the fragments.