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Barrel Thread Concentricity GO/NO-GO Gauge 5/8-24 7.62mm Threaded Barrels


This gauge will allow you to check whether the 5/8-24 threads on a 7.62mm weapon are concentric with the bore. Most sound suppressor manufacturers list 0.003″ (3 thousandths of an inch) as a standard tolerance for thread concentricity.

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This tool will allow you to see if your barrel is within this specification. If the pin does not slide freely into the barrel, this means your threads are out by at least 0.003”. This could cause a sizable point of impact shift and possible baffle strikes.

  • Simply hand-tighten the knurled body section onto your threads.
  • Drop the bore alignment pin into the hole on the knurled body.
  • Use a light touch to insert the pin. Very little/no force should be needed.
  • If the threads are within 0.003, the pin should slide freely all the way down.
  • If the pin stops halfway or does not go in at all, do NOT force the pin, your threads are likely outside of the tolerance.

If the pin does not slide freely, it is advised to have your barrel inspected by a competent gunsmith.

This device is not an absolute guarantee of concentricity. 

The pin is made of O-1 tool steel, hardened to 50 Rockwell C, then ground to size.

This pin is ground to fit most all 7.62 rifling.

*The pin is made of steel and will rust if not maintained with a light coating of oil.