On a media day at Aberdeen Proving Ground on 4 May 2011, reports were given about the M855A1's performance in the field since it was issued 11 months earlier. One primary advantage given by the round is its consistent performance against soft targets. While the older SS109/M855 was yaw-dependent, which means its effectiveness depends on its yaw angle when it hits a target, the M855A1 delivers the same effectiveness in a soft target no matter its yaw angle. The new SMP-842 propellant in the round burns quicker in the shorter M4 carbine barrel, ensuring less muzzle flash and greater muzzle velocity. The M855A1 was able to penetrate of mild steel plate at . The round even penetrated concrete masonry units, similar to cinder blocks, at from an M16 and at from an M4, which the M855 could not do at those ranges. Its accuracy is maintained and sometimes increased, as it was able to shoot a group 2 inches better at . February 2011 was the first time the M855A1 was used more than the M855, and approximately 30 million M855A1 rounds have been fielded from June 2010 to May 2011.