Factory Specified Size Measures M16/AR-15 Maximum Headspace
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.
AR-15, Issue:09, Page:076
AR-15, Issue:09, Page:080
Big Book Catalog, Issue:67, Page:078
Big Book Catalog, Issue:67, Page:083
Law Enforcement / Police Store, Issue:08, Page:054
SPECS: Hardened and ground steel. 1.65" (4.2cm) overall (this is NOT the "headspace" dimension). .3655" (9.3mm) diameter.