Barnes offers bullets featuring Multi-Purpose Green (MPG) technology developed for military and law enforcement applications. MPG bullets feature a highly frangible, powdered-metal copper-tin core inside a guilding metal jacket. Unlike frangible bullets lacking a protective jacket, MPG bullets remain intact under the rigors of handling, feeding and firing. This eliminates the primary cause of jammed actions and plugged barrels often experienced when firing frangible ammunition. The 55 grain 5.56mm (.224) MPG bullet is designed for M4, HK416 and AR-15 type autoloaders and other firearms with rifling twist rates of 1:9 inches or faster. These open-tip bullets remain intact at ultra-high velocities and extreme rates of spin. On impact, they deliver explosive fragmentation. Barnes Multi-Purpose Green bullets are exceptionally accurate. They're ideal for shooting steel targets, competition, plinking, varmint hunting and home defense. "Green" is military shorthand for "lead-free" - a requirement in military and LE practice environments. 1:9 inches or faster twist rate