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  #31  
Old 02-12-2013, 11:18 PM
aljkw aljkw is offline
 
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Barrel issue..or real close to a barrel issue
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  #32  
Old 02-12-2013, 11:35 PM
jmm jmm is offline
 
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Quote:
Originally Posted by TGR View Post
So if it closes on a field Gauge, do I look for a bolt with less wear? Or are we talking a barrel issue?
Somewhere there is a list of bolts giving some as longer than others. A big "maybe" on your cure, but it may just be changing to a new bolt.
...a quick "google" seems to indicate that the -19 and 65 series bolts are slightly longer. start searching the forum for info on "headspace" and "bolt replacement".
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  #33  
Old 02-12-2013, 11:40 PM
TGR TGR is offline
 
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The new bolt is a -19, with some wear. Just picked it up from another member. I wonder if one closer to NOS condition could help. Field Gauge on back order.
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  #34  
Old 02-13-2013, 01:43 PM
Unclenick Unclenick is offline
 
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Normally you change the barrel. A different bolt might help, but you want to take the rifle with you to the bolt store to tell. That's the tricky part. If the barrel was swapped in from another gun, your bolt may not have enjoyed normal setback allowance. Do inspect your existing bolt for lug cracks.
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Last edited by Unclenick; 02-13-2013 at 01:51 PM.
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  #35  
Old 02-20-2013, 11:23 PM
TGR TGR is offline
 
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Ok, got the Clymer Field Guage today. The bolt passed, with a no-close on the field guage. I have included a few pics. Can someone confirm this is what it should look like. Thanks.

Closed on No-Go Guage

http://www2.snapfish.com/snapfish/fe...A%22s%22%7D%7D

Would not close on the Field Guage

http://www2.snapfish.com/snapfish/fe...A%22s%22%7D%7D

Last edited by TGR; 02-21-2013 at 10:20 AM.
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  #36  
Old 02-21-2013, 11:01 AM
Unclenick Unclenick is offline
 
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Those two links are identical and take me to the Snapfish home page where it asks me to log in, so I don't see your photos. I notice in Wikipedia they say Snapfish announced it would stop its file hosting service in 2008, but that pictures on it could still be linked to as of January this year. It doesn't sound like it's in reliable shape for hosting photos for forum posts. You might want to look at Image Shack or Photobucket or one of the other file hosting services as a replacement.

Basically, though, if you try to rotate the bolt closed with your thumb pushing down on the lug extension (the stub that engages the recess in the op-rod hump when the rifle is assembled), it should stop before it rotates all the way to the closed position. The means the bottom of the right side lug and stub will not quite touch down on the receiver.

From the Nicolaus Garand blueprint book, the outside edge of the bolt lug engagement surface is at a 0.635" radius. The pitch angle is 0.2", so when the outside edge of the bolt lug on the op-rod side has a 0.1" gap short of stopping against the receiver, the chamber is 0.005" short of closing. Note that the gap should ideally be measured as a circumference length rather than a straight measurement across the gap, but the two are close to the same when the angle is small and it doesn't make any practical difference. The bottom line is gap in inches times 50 will give you the number of thousandths you have left for the headspace to grow.

Normal practice is for a commercial GO gauge to be at SAAMI chamber minimum and the FIELD gauge to be at SAAMI chamber maximum. The NO-GO is somewhere inbetween, but no SAAMI standard exists for this. The idea is that a newly cut chamber not exceed the NO-GO length in order to allow for a little mating surface flattening and lug setback during the life of the barrel that will increase the headspace. In .30-06 the SAAMI chamber maximum is the minimum +0.0100", so that is the FIELD gage dimension. Clymer says their NO-GO is -0.004" shorter than the FIELD gage to make that barrel life allowance.

So I would expect the bottom your bolt lug to be somewhere between about 0.08" short of contacting the receiver and actually making contact. If you measure the gap in inches and multiply by 50, as I described, you will have the number of thousandths left for headspace growth before it closes on the FIELD gage. Feeler gages will work to make the gap measurement.
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Last edited by Unclenick; 02-21-2013 at 11:47 AM. Reason: typo fixes
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  #37  
Old 02-21-2013, 11:28 AM
TGR TGR is offline
 
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Ok, Lets see if this works.


Closed on No-Go Guage

http://s1145.beta.photobucket.com/us...tml?sort=6&o=0


Not closed on Field Guage

http://s1145.beta.photobucket.com/us..._5288.jpg.html
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  #38  
Old 02-21-2013, 11:53 AM
Unclenick Unclenick is offline
 
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I can get that in IE, but not Firefox due to script blockers. But that looks good. I'm going to eyeball guestimate that you've got 0.003" left for headspace to grow, so you are 0.007" above minimum headspace and 0.001" over NO-GO. That's exactly what my original DCM Garand's barrel had. I've labeled a cut from your second photo, below:

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  #39  
Old 02-21-2013, 12:01 PM
TGR TGR is offline
 
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Great. Thanks for sharing the knowledge. I'll measure it tonight and let you know how close your guestamate was.

It's an origanal Aug 44 barrel and receiver that's got some stories I'm sure. Finally got the correct bolt for it.
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  #40  
Old 06-18-2013, 10:17 PM
John Gault John Gault is offline
 
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Great write up with great Pics. Valuable! Thank you!
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