Lead is a very effective component in military bullets. The density of lead gives any bullet a higher ballistic coefficient than it would have if it were made of a less dense metal like copper. Lead is soft enough to expand upon striking a target, and yet has sufficient ductility and tensile strength to hold together while penetrating. I don’t think the military should give up using lead bullets anytime soon. But for whatever reason, there is a strong push for lead-free “green” bullets in the U.S. military today.
One of the problems with the current generation of lead-free military bullets is their inability to expand or fragment. They rely on yaw to increase their effectiveness once a target is struck. But as explained in a previous post, expansion (mushrooming) is more reliable than yaw or fragmentation for incapacitating an enemy combatant.
While it is true that the Hague Convention of 1899 prohibits expanding bullets in warfare, the United States never formally ratified that treaty. The intention behind the prohibition was to prevent the use of bullets that would cause prolonged suffering before death, as was the case with the dum-dum bullets of that time period. However, modern expanding bullets are designed to the opposite effect, even when used on animals. They provide a quick kill with less suffering. So we should adhere to the spirit of the law, not to its letter.
Can we make a lead-free bullet that expands? There are several similar designs on the commercial market right now. They all use about the same approach. A copper or copper alloy bullet is designed to peel back several petals, once it strikes a target. Hunters seem happy with this type of bullet, even preferring it over lead bullets for some purposes.
The military could adopt one of these commercial offerings as a new “green” military round. But the current selection of bullets tend to expand only at higher velocities. A military bullet must expand over a wide range of velocities, so as to be effective over a wide range of distances. Also, the military would prefer a bullet with a steel penetrator tip. Such a tip would prevent that type of bullet from expanding.
My suggestion is that the military develop a copper core bullet that expands. The basic design would be similar to many hunting bullets. But instead of a lead-alloy core with a copper-alloy jacket, two different alloys of copper would be used: the usual copper-alloy jacket, and a soft copper-alloy core that would have similar properties to a lead-alloy core. The soft copper core should expand easily, down to velocities as low as 1300 fps. And it should hold together at velocities up to 3200 fps.
Then, instead of the polymer tip that many lead-core bullets use to initiate expansion, these new “green” bullets could use a steel tip of about the same shape. The steel tip should allow the bullet to penetrate a variety of barriers well, while the soft copper core should offer good expansion. The base of the bullet, as part of the jacket, will be made of the harder copper-alloy. A thick base will allow the bullet to retain most of its weight in order to penetrate a target.