Compact Assault Rifle - 5.56x45mm NATO - USA - 825 RPM - The M4A1 (Colt Model 927) is the most recent variant of the CAR15 family.  The barrel length was specially selected to provide compactness without sacrificing reliability.  The barrel is also contoured to provide for the attachment of a M203 grenade launcher.  In addition, improved handguards with double heat shields have been added to prevent the uncomfortable heating properties of earlier CAR15s during rapid fire. D.E. Watters