The Adams Arms Piston system is a short stroke free floating piston system. The system is self-cleaning carbon and gases are expelled forward away from operator and it doesn't vent directly to atmospheric pressure. This eliminates flash signature and super sonic crack which is optimal for night vision and suppresses fire. Corrosive resistant coating protects the rifle from weather and fouling. An adjustable gas block provides settings for various applications. - Doesn't vent directly to atmospheric pressure; this eliminates flash signature and super sonic crack which is optimal for night vision and suppresses fire. The Mid-Length Base model has a short 14.5" barrel with permanently pinned VDI Manimal Flash Hider to bring it back to a legal 16".