Green bullet
Green bullet, green ammunition or green ammo are nicknames for a United States Department of Defense program to eliminate the use of hazardous materials from small arms ammunition and from small arms ammunition manufacturing. Initial objectives were elimination of ozone-depleting substances, volatile organic compounds, and heavy metals from primers and projectiles. These materials were perceived as causing difficulties through the entire life cycle of ammunition. The materials generated hazardous wastes and emissions at manufacturing facilities and use of ammunition caused contamination at shooting ranges. Potential health hazards made demilitarization and disposal of unused ammunition difficult and expensive.[2]
The Joint Working Group for Non-Toxic Ammunition was formed by the Small Caliber Ammunition Branch of the United States Army Armament Research, Development and Engineering Center in October 1995. Members of the working group included the National Guard of the United States, the United States Coast Guard, the United States Army Infantry School, the Industrial Operations Command, the Lake City Army Ammunition Plant, the Oak Ridge National Laboratory, the Los Alamos National Laboratory and the United States Department of Energy Kansas City Plant.[2]
Legislation[edit]
October 11, 2013 Governor Jerry Brown of California signed into law AB 711 Hunting: nonlead ammunition.[5] Cost reductions from conversion to green ammo are estimated at "$2.5 million required for waste removal at each outdoor firing range as well as the $100 thousand annual costs for lead contamination monitoring".[6]
Wildfire considerations[edit]
Some of a bullet's kinetic energy is typically converted to heat if the bullet strikes a hard surface like rock. Collision debris may include high temperature bullet fragments as sparks. Steel core and solid copper ammunition have the highest potential to start wildfires. Lead core bullets are less likely to ignite surrounding vegetation.[22][23]
Rifling considerations[edit]
Rifling is required to stabilize elongated bullets, and longer bullets require faster rotation for similar stability. The rate of rotation is determined by the twist of the lands and grooves engraved on the interior of a rifled barrel. Twist is usually expressed as the length of barrel (in inches) in which the bullet will rotate through a full 360 degrees; so bullets fired from a 1:10" twist rifle will make a complete rotation in every 10 inches (25 cm) of distance traveled.[24]
Since lead is a very dense material, bullets made of inexpensive, non-toxic materials will be lighter than bullets made of lead unless bullet length is increased. Inferior external ballistics cause lighter bullets to be less effective against distant targets. Increasing bullet length may require a faster rifling twist to maintain stability. Some early trials versions of the M16 rifle had 1:14" twist barrels, but this was increased to 1:12" twist in early military production to improve stability with 55-grain (3.6 g) M193 lead-core bullets in the early 5.56×45mm NATO cartridges. Twist was increased to 1:9" after combat experience demonstrated the advantages of longer 62-grain (4.0 g) M855 bullets with a portion of the lead core replaced by a less dense steel penetrator. Barrels with 1:7" twist have been used in 21st century 5.56×45mm NATO firearms and have replaced barrels of older United States military firearms to stabilize longer M856 tracer bullets and M855A1 green bullets of less dense materials.[25]