Frangible bullet

Bullets designed to reduce ricochet risk

Frangible bullets are intended to disintegrate into tiny particles upon target impact to minimize their penetration of other objects. Small particles are slowed more rapidly by air resistance, and are less likely to cause injury or damage to persons and objects distant from the point of bullet impact. Most frangible bullets are subject to brittle failure upon striking a hard target. This mechanism has been used to minimize the tendency of malleable lead and copper bullets to ricochet from hard targets as large, cohesive particles. Brittle failure may occur at subsonic velocity. Attempting to crimp a brittle frangible bullet into the cartridge case may break the bullet. Brittle frangible bullets may break during the self loading cycle of semi automatic firearms; and those fired from revolvers often break as the bullet encounters the barrel forcing cone after leaving the cylinder.

Powder metallurgy techniques fabricate bullets from mixtures of powdered metals (typically tin, copper, zinc, and/or tungsten) compressed at room temperature to produce a high density material. Mechanical interlocking and cold welding bond the metals together either pressed directly to shape, or into bar stock billets that can be swaged into projectiles, with or without jacketing. Frangible hollow point bullets may penetrate clothing, drywall, and light sheet metal; but often disintegrate upon striking glass. Hard targets may be damaged by frangible bullets. Extent of damage increases with velocity of bullet impact. Energy transfer at the point of impact may break brittle targets, and may temporarily soften and permanently deform malleable materials. Target crystalline structure may be changed to increase target damage by subsequent bullets. Steel targets designed to withstand rifle ammunition may be damaged by bullet velocities over 2700 feet (823 m) per second; and lower velocity bullets may damage steel targets intended for pistol or rimfire ammunition. Some penetrate soft tissue similar to full metal jacket bullets. Some may disintegrate upon striking bone. Hunting bullets include a frangible core designed to disintegrate when a protective jacket is opened by softer tissue or fluid. Frangible bullets disintegrating in flesh cause very serious wounds with persistent effects. Frangible bullets may represent an unconventional threat to personal armor intended to resist traditional lead bullets. At the request of the National Institute of Justice, staff of the Office of Law Enforcement Standards, located at the National Institute of Standards and Technology, has conducted a limited series of tests evaluating the performance of frangible ammunition against body armor. This preliminary study was designed to attempt to establish the validity of claims that these types of rounds pose a potential safety threat to personal body armor. The true scope and relevance of this threat was not known as of November 2002.

Injuries from lead bullet fragments ricocheting off metal targets at 20th century amusement park shooting galleries encouraged development of frangible bullets in specialized .22 Short gallery loads including Peters Krumble Ball, Remington Spatter Less, Western Kant Splash, and Winchester Spatterpruf. The United States used frangible lead/Bakelite M22 bullets in aircraft .30 caliber machine guns for target practice at armored RP 63 manned target aircraft. The lower density M22 bullets were of the same shape as conventional M2 bullets for reliable function through self loading machine guns, but weighed only in comparison to for the M2 bullets. In the early 21st century, the United States military began using frangible bullets to reduce ricochet risk during small arms training. These bullets use nylon as a binding agent for a core of powdered copper and tungsten contained within a gilding metal jacket. A tungsten/nylon projectile core was developed by Ecomass Technologies to replace the lead core in the 3 part M855 5.56mm projectile and placed in service between 2000 and 2003. This projectile core performed similar to the lead core with the same, or better, accuracy.