223 Remington, Headspace Gauge

223 REM: Used to check headspace of 223 Rem and 6mm x 45 RIMLESS CARTRIDGE HEADSPACE: The proper use of Headspace Gauges is the most reliable way to test rifle chamber length. Headspace in a rimless cartridge is the distance between the bolt face and a datum line, determined by SAAMI, where the front of the cartridge rests on its shoulder when the bolt is closed. FIELD: FIELD Gauges are slightly shorter than the SAAMI maximum in order to give a small safety margin. If a rifle closes on a FIELD Gauge, its chamber is dangerously close to, or longer than, SAAMI-specified maximum chamber size. If chamber headspace is excessive, the gun should be taken out of service until it has been inspected and repaired by a competent gunsmith. PRECISION MACHINED: Manufactured from top-quality, hardened steel and precision ground to ANSI and SAAMI tolerances. Headspace tolerance ground to a very exacting ±.00015. Each Headspace Gauge thoroughly inspected with NIST-certified measurement tools to ensure