5.56mm Maximum Headspace Gauge - Brn Ar-15/M16 Colt 5.56x45 Nato Headspace Gauge 1.4736''''

Made to the Colt factory's special dimensions for M16/AR-15 rifles. It measures the maximum factory acceptable headspace; an essential check on guns that have seen extensive service or have been rebarreled. Mfg: Brownells SPECS: Hardened and ground steel. 1.65" (4.2cm) overall (this is NOT the "headspace" dimension). .3655" (9.3mm) diameter.