1. It delivers a hydrostatic shock wave that travels out from the bullet’s path and into the animal’s body that has received the bullet, causing significant damage to internal organs and bones.
2. It ensures that when the bullet tumbles through the body, the increased diameter and sharp edges of the expanded bullet causes more internal physical damage to the animal.
However, one other consequence of a rapidly expanding lead bullet traveling at more than twice the speed of sound is that some of the soft metal itself erodes away from the frontal section of the bullet as it strikes and travels through the animal.
Lead bullet fragmenting as it travels through the body
This .270, 130 grain Remington Core-Lokt bullet was discharged and retrieved and found to have lost 32% of it's original mass due to fragmentation. Contrast this bullet with a .270 cal Barnes Triple Shock copper bullet at the bottom of the page.
Another Core-Lokt bullet was fired into ballistic gelatin and then x-rayed. The non-lead bullets depicted above and below lack the fragmentation of the lead-core bullet in the middle.
Why Lead Fragments Matter
It's this fragmenting characteristic of lead bullets that is cause for concern for wildlife and humans who eat any portion of an animal shot with this type of bullet. While efforts have been made to retain the expanding characteristic of lead bullets, but eliminate the fragmenting aspect (e.g. special bonding of the jacket to the bullet core), none have been entirely successful in this regard.
The facts are clear based on valid scientific studies that have been conducted (Minnesota DNR, The Wildlife Society Bulletin) - full text (PDF)
Lead-core bullets WILL fragment to varying degrees depending on:
- Where the bullet strikes (Bone will cause bullets to break apart much more than flesh/organs).
- Composition of bullet (soft point bullets fragment the worst; bonded-core fragment the least).
- Speed of the bullet (higher muzzle velocities mean greater fragmentation, all other things being equal).
Lead Fragments in Animals
Neck-shot Mule Deer
Dark spots are lead bullet fragments
Close-up of photo from above. Note the fractured spine and hundreds of small lead fragments.
More Lead Bullet Fragmentation in Whole Animals
Rim-fire Bullets and Fragmentation
Yellow-bellied marmot shot with a lead .22 caliber bullet
Non-lead Bullet Alternatives
Barnes Triple Shock Bullet - .270 caliber
Luckily, newer alternatives made of either 100% copper or copper-zinc alloys exist that expand similarly to lead-core bullets but without the extensive fragmentation.
Bullet Expansion and Energy Transfer
Rapid and controlled expansion of a rifle bullet is necessary so that the kinetic energy present in a speeding projectile is transferred into the tissues of the animal being hunted. Non-lead bullets do not fragment like lead-core bullets and therefore, often pass through the animal. Some suggestions have been made that this will result in insufficient energy transfer because too much of the bullet’s energy is “wasted” if the bullet exits. In order to test this assertion, we compared energy transfer for both lead and non-lead bullets and found that the differences were small. This is because since the non-lead bullets exit at a slower velocity compared to their entrance velocity, the bulk of the energy has already been expended in the animal. This is important because bullet energy is computed with a formula that takes the bullet’s speed and squares it, so that a relatively small change in velocity results in a much greater change in bullet energy.
< Chronograph set up in front of gel block to measure incoming velocity
Chronograph set > up to measure bullet velocity as it exits the gel block
We then used the following formula:
We tested the following bullets in .270 Win. and .30-06 Spr calibers:
Lead-core: Remington Core-Lokt
Nonlead: Barnes Triple Shock and Tipped Triple Shock, Remington Copper Solid, Nosler e-Tip, and Hornady GMX
As shown in the graph, when bullets were fired into a relatively thin 10" ballistic gel block, non-lead bullets expended similar amounts of total energy as did the lead bullets. Also, it's worth pointing out that a 110 grain .270 cal non-lead bullet expended MORE energy than a heavier 180 grain, 30 cal lead bullet. This was due to the 110 grain bullet entering the gel at ~3100 ft/sec, which gave it a proportionally much greater amount of kinetic energy than a slower, but heavier lead bullet.