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-   -   Headspacing (How to). (http://forums.thecmp.org/showthread.php?t=3767)

Ericc 12-14-2009 05:03 PM

Headspacing (How to).
 
With all the requests for information on headspacing, I figured it was time to get a post up in the new forums.


Step 1. Clean the rifle chamber leaving no cosmoline or other material that would effect the measurements. If you have a chamber brush, use it. Remove any other grease, oil, and cosmoline from the action, including the locking lugs on the bolt and receiver.

Step 2. Strip the bolt. [Instructions]. Clean the bolt face at this time.

Step 3. Strip the action of the operational parts. [Instructions]

With the parts removed and your bolt stripped your setup should like the image below. (You do not need to remove the rear sight as shown below.)

http://www.garandgear.com/media/tutorials/Head1.jpg

Step 4. Insert the GO gauge gently into the chamber and install the stripped bolt into the receiver.

Step 5. Using finger pressure only, push the bolt closed. The bolt locking lug should look like the image below. The lug MUST be all the way down and contacting the receiver to pass the GO test.

[GO Gauge]
http://www.garandgear.com/media/tutorials/Head4.jpg


Step 6. Remove the GO gauge and install the NO-GO gauge. Using finger pressure only, push the bolt closed. The bolt locking lug should look like the image below. The lug MAY be all the way down and contacting the receiver. This does not yet indicate a rifle with excessive headspace. On a NEW barrel the locking lugs will look as shown below. As headspace increases the locking lug will move down toward the receiver.

[NO-GO Gauge]
http://www.garandgear.com/media/tutorials/Head5.jpg

Step 7. Remove the NO-GO gauge and install the Field gauge. Using finger pressure only, push the bolt closed. The bolt locking lug should look like the image below. The lug MUST NOT be all the way down and contacting the receiver. If the lug touches the receiver the rifle has excessive headspace. On a NEW barrel the locking lugs will look as shown below. As headspace increases the locking lug will move down toward the receiver.

[FIELD Gauge]
http://www.garandgear.com/media/tutorials/Head6.jpg

Step 8. Inspect your parts for wear and Re-assemble and lubricate appropriately.

Results:

[My Bolt wont close on a GO gauge!]

1. Did you remember to strip your bolt? Did you verify your chamber is clean and free of obstructions? Did you use the correct gauge?

2. Is your barrel new and not yet finish reamed? Did you accidentally swap bolts with another Garand?

[My Bolt closed on a NO-GO gauge!]

1. The NO-GO gauge is an intermediate gauge and by itself does not indicate excessive headspace. The results of the Field test will let you know if you have an issue.

[My Bolt closed on a FIELD gauge!]

1. Is the bolt locking lug actually touching the receiver? See image of the GO gauge test to see what fully locked looks like.

2. If the bolt lug is fully closed then your barrel/bolt combination has reached the end of its service life (In terms of head space). There are options available besides changing the barrel. I wont cover those here so ask on the forum.

Hopefully this will be useful to someone. Please let me know if I messed up something so it can be corrected.

Eric




MEUSOC 03-11-2010 07:41 PM

I thought this was a great write-up.

Ericc 03-11-2010 09:29 PM

Quote:

Originally Posted by MEUSOC (Post 83350)
I thought this was a great write-up.

Thanks. Hopefully it will be useful to someone.

Eric

jeeperbob 03-12-2010 08:06 AM

Very nicely done. You probably meant to reverse steps 2 & 3 to be able to get the bolt out prior to stripping. Although gages with the cut outs, commercial type escapes me and military gages, the best way is as you have shown because if not inserted correctly can give false readings for the unschooled. Dissassembly of the bolt removes any possibility of error. You will get responses that say you only need the field gage or some combination but the best way is to check with all three as you have done. IMHO folks who don't have the money to get all three probably shouldn't be doing this activity. The average person who only has a couple rifles and doesn't engage in armorer activities on a routine basis are better off paying a modest fee for a qualified gun plumber to do the checks. Again IMHO. Liked the pix.

Jeremy2171 03-12-2010 09:08 AM

Good write up however I'd probably leave out the part on the NOGO. That gage has no real purpose unless you are installing new barrels. The GO and FIELD should be the ones used.

Ericc 03-12-2010 04:18 PM

Quote:

Originally Posted by Jeremy2171 (Post 83668)
Good write up however I'd probably leave out the part on the NOGO. That gage has no real purpose unless you are installing new barrels. The GO and FIELD should be the ones used.

The no-go was included to be complete. Otherwise questions will arise to its purpose.

Eric

rtohio 12-06-2010 06:15 PM

Very nicely done and very informative.

Callahan 12-07-2010 06:35 AM

Nice work Ericc. Explained very well, backed up with great pics.

en bloc 12-09-2010 04:25 PM

Moderator; Please make this post a STICKY
 
Nice work Ericc.
This post should be made STICKY for posterity.

~Matt

en bloc 12-09-2010 04:33 PM

Forsters vs. Clymers
 
Could you shed some light on the difference between these tests and the two gauge manufacturers.

I have not performed these tests yet and have just received a set of (3) Forsters gauges.

CMP, I found after purchase, uses Clymer. Can successful tests be made with Forsters?

Thanks,
~Matt


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