How to Use a Headspace Gauge

I got permission from islandhopper to put up a copy of his step by step instuctions on how to use a headspace gauge in a Garand's receiver. It was too good NOT to disseminate.

Thank you, sir.

This was the forum I saw it on.



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Make sure you have stripped the bolt, even if your gauge has the extractor cut-out. What brand gauge are you using? Forster tends to run a little bit short. I use them, but in this case you may want to try a Clymer or USGI gauge.

How to Check Headspace

1. Remove the receiver/barrel assembly from stock.

2. Remove the follower rod and operating rod spring.

3. Remove the operating rod.

4. Remove the bolt.

5. Disassemble/strip the bolt.

6. Make sure that the barrel chamber and bolt face are clean and free of grease, oil and debris.

7. Re-insert disassembled/stripped bolt into the receiver.

8. With the disassembled/stripped bolt approximately half-way retracted from the breech, partially insert a Go Gauge into the chamber.

9. Holding the Go Gauge from underneath the receiver with the index and/or middle finger of the right hand, use the thumb and index finger of the left hand to GENTLY move the bolt forward so that the rear of the Go Gauge is fully seated against the bolt face.

10. GENTLY move the bolt forward, allowing the bolt lug to seat on its own on the bottom of the receiver notch without additional pressure or force. As the bolt is moved into place, there should be no resistance while using very light finger pressure to move the bolt. For headspace to be sufficient, the bolt lug needs to be fully seated against the bottom of the receiver notch with the Go Gauge in place and without resistance.

11. Move the bolt back and remove the Go Gauge.

12. Repeat steps seven through 10 with the No Go Gauge. The bolt lug SHOULD NOT seat against the bottom of the receiver notch with the No Go Gauge in place. In other words, if the bolt fully closes on the Go Gauge and does not fully close on the No Go Gauge, headspace is sufficient and correct. If the bolt closes on both the Go Gauge and the No Go Gauge, a Field Gauge must be used to determine if the headspace is excessive and unsafe.

13. Move the bolt back and remove the No Go Gauge.

14. Repeat steps seven through 10 with the Field Gauge. If the bolt lug does not seat against the bottom of the receiver notch with the Field Gauge in place, headspace is still sufficient and not excessive. Therefore the bolt CAN close on the Go Gauge and on the No Go Gauge, but as long as the bolt DOES NOT close on the Field Gauge, headspace is still considered sufficient and correct. If the bolt closes on all three gauges (the Go Gauge, the No Go Gauge and the Field Gauge), headspace is excessive and the rifle is not safe to fire. A new barrel or bolt may rectify the headspace issue; however the receiver may also have excessive wear and may be a contributing factor as well.

Headspace Summary

1. Bolt does not close on Go Gauge – insufficient headspace and barrel chamber needs to be finished reamed to at least 1.940.

2. Bolt closes on Go Gauge but does not close on a No Go Gauge – headspace is correct.

3. Bolt closes on Go Gauge and No Go Gauge, but not on a Field Gauge – headspace is correct.

4. Bolt closes on Go Gauge, No Go Gauge and Field Gauge – headspace is excessive and barrel, bolt or even possibly the receiver will need to be inspected for replacement.

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