There have been several new types of 5.56 MM small arms ammunition developed and issued to troops in Afghanistan to give the M16 rifle and M4 carbine enhanced accuracy at longer ranges and more penetration through hard targets. In June of 2010 the U.S. Army announced it had begun shipping its new 5.56MM cartridge, the M855A1 Enhanced Performance Round, to active combat zones. During testing, the M855A1 performed better than current 7.62x51 NATO ball ammunition against certain types of targets (particularly hardened steel), blurring the performance differences that previously separated the two cartridges. The U.S. Army Picatinny Arsenal stated that the new M855A1 offers improved hard target capability, more consistent performance at all distances, enhanced dependability, improved accuracy, reduced muzzle flash, and higher velocity compared to the M855 round. Further, the army stated that the new M855A1 ammunition is tailored for use in M4 carbines but should also give enhanced performance in M16 rifles and M249 light machine guns. The new 62 grain bullet used in the M855A1 round has a copper core with a 19 grain steel "stacked cone" penetrating tip. The M855A1 cartridge is sometimes referred to as "green ammo" because it fires a lead free projectile.
Another new developement is the Mk 262 round. This is a match quality round developed and manufactured by Black Hills Ammunition made originally for the Special Purpose Rifle. It uses a 77 grain bullet that is more effective at longer ranges than the standard issue M855 round. According to US DOD sources, the Mk 262 round is capable of making kills at 700 meters. Ballistics tests found that the round caused "consistent initial yaw in soft tissue" at 300 + meters. Apparently it is superior to the standard M855 round when fired from an M4 or M16 rifle. It evidently possesses superior stopping power, and can allow for engagements to be extended to up to 700 meters. It appears that this round can drastically improve the performance of any AR15 platform weapon chambered to 223/5.56MM. Superior accuracy, wounding capacity, stopping power and range power has made this the preffered round of many Special Forces operators, and highly desirable as a replacement for the older, Belgian designed 5.56x45mm M855 NATO round.