#2 The M855 is a lead bullet with a steel core.
The M855A1 is a tungsten bullet with a copper wrapped steel core.
During testing, the M855A1 performed better than M80 7.62×51mm NATO ball ammunition against certain types of targets (particularly hardened steel), blurring the performance differences that previously separated the two cartridges. The US 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 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 (4 g) projectile or bullet used in the M855A1 round has a copper core with a 19-grain (1.2 g) steel "stacked-cone" penetrating tip. The M855A1 cartridge is sometimes referred to as "green ammo" because it fires a lead free projectile.[67][68][77][78][79][80] It is not necessarily more lethal than the M855, but performs more consistently every time it hits a soft target and retains its performance at longer distances. The EPR can penetrate a 3⁄8 in (9.5 mm) thick steel barrier from an M4 at 350 meters and from an M16 at 400 meters. Ballistics for both rounds are similar and don't require weapons to be re-zeroed, but if they are the EPR can be slightly more accurate. The steel-tip penetrator of the M855A1 is noticeably separated from the jacket of the bullet and can spin, but this is part of the design and does not affect performance. The M855A1 costs only 5 cents more per round than the M855.[81] The M855A1 bullet has a 1⁄8 in (3.2 mm) greater length than the M855.[82] Because steel and copper are less dense than lead, the bullet is lengthened inside the case to achieve the same weight as its predecessor. |