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  #1  
Old 12-14-2009, 06:03 PM
Ericc Ericc is offline
 
Join Date: Oct 2009
Posts: 2,496
Default 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.)



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]



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]


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]


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




Last edited by Ericc; 06-01-2015 at 05:27 PM. Reason: Updated Images
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  #2  
Old 03-11-2010, 08:41 PM
MEUSOC MEUSOC is offline
 
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I thought this was a great write-up.
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  #3  
Old 03-11-2010, 10:29 PM
Ericc Ericc is offline
 
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Quote:
Originally Posted by MEUSOC View Post
I thought this was a great write-up.
Thanks. Hopefully it will be useful to someone.

Eric
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  #4  
Old 03-12-2010, 09:06 AM
jeeperbob jeeperbob is offline
 
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Location: Vail, AZ
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Default

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.
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Last edited by jeeperbob; 03-12-2010 at 09:19 AM.
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  #5  
Old 03-12-2010, 10:08 AM
Jeremy2171 Jeremy2171 is offline
 
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Posts: 763
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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.
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  #6  
Old 03-12-2010, 05:18 PM
Ericc Ericc is offline
 
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Quote:
Originally Posted by Jeremy2171 View Post
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
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  #7  
Old 12-06-2010, 07:15 PM
rtohio rtohio is offline
 
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Very nicely done and very informative.
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  #8  
Old 12-07-2010, 07:35 AM
Callahan Callahan is offline
 
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Nice work Ericc. Explained very well, backed up with great pics.
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  #9  
Old 12-09-2010, 05:25 PM
en bloc en bloc is offline
 
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Default Moderator; Please make this post a STICKY

Nice work Ericc.
This post should be made STICKY for posterity.

~Matt
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  #10  
Old 12-09-2010, 05:33 PM
en bloc en bloc is offline
 
Join Date: Nov 2010
Location: Massachusetts
Posts: 252
Default 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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