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Headspacing question

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richg072 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote richg072 Quote  Post ReplyReply Direct Link To This Post Topic: Headspacing question
    Posted: Jan 26 2018 at 6:26pm
Ok so I may of asked a couple people on this already but I still don't think I have a definite answer, likely because I didn't explain it correctly.   I think I know the basic of head spacing,  but then I find conflicting info.  Any way I had a barrel mounted to a receiver I had by a reliable GS who also checked head spacing with the bolt I provided.  He explained to me that it passed but it head spaced long and that the barrel might be towards the end of its life.  Here is exactly what is on the service tag which confuses me a bit.  "Head Space is long but passable.  No close on 1300 partial close on 1298"  
Is this something that can possibly be corrected with a different bolt or is the barrel just done?  

Something that is concerning me is the bolt he used to check H/S was purchase from a same seller in which that bolt was used for a different project that also had H/S issues.  Both bolts were listed well under usual selling prices.  I'm just wondering is this just a worn bolt issue?  But do the numbers above tell a better story to anyone?  
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Post Options Post Options   Thanks (0) Thanks(0)   Quote floydthecat Quote  Post ReplyReply Direct Link To This Post Posted: Jan 26 2018 at 7:17pm
It is never suppose to close on a field-gauge. Depending on who's brand of gauge you purchase...that figure can vary slightly, but 1.300 is a good number. The figures above indicate the action is still good...if it won't close on a 1.300. BUT....if it almost closes on a 1.298, you don't have a lot of life left in it. Your figures tell me the gun is safe to shoot now, but will soon require attention.

I doubt if arbitrarily finding a bolt to tighten it up is practical....unless you have access to a large quantity of bolts that you could try. It's my understanding that a worn barrel can possibly be machined and re-fitted one time, but the GS has to know what he's doing. It may be best for you to be thinking about a new barrel in the near future, but that depends on how much shooting you plan to do with it.
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richg072 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote richg072 Quote  Post ReplyReply Direct Link To This Post Posted: Jan 26 2018 at 7:26pm
Ugh, finding correct barrels is impossible.  Cry     Something else that I forgot to mention above that makes me scratch my head is the MZ is just a little over a 1.  I know two completely different subjects but if it was shot enough to wear out head spacing, wouldn't MZ wear down also from a lot of cleaning and such ? 
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Post Options Post Options   Thanks (0) Thanks(0)   Quote W5USMC Quote  Post ReplyReply Direct Link To This Post Posted: Jan 26 2018 at 7:34pm
Sounds like one of my carbines. With the well worn round bolt that is currently in it, it will close on my Clymer no-go gauge but not on my Forster Field (1.299) gauge. Still in specs and serviceable. I did play around a bit and checked the headspace again with a different (flat) bolt and got much better results, closed only on the Go Gauge.   
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sling00 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote sling00 Quote  Post ReplyReply Direct Link To This Post Posted: Jan 26 2018 at 7:36pm
It does seem odd with a MW of 1 that the barrel is shot out.   Just throwing this out there...Any chance you can measure TE?  
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jackp1028 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote jackp1028 Quote  Post ReplyReply Direct Link To This Post Posted: Jan 26 2018 at 7:53pm
I believe your gunsmith is correct in stating that your barrel is near the end of its life. I also agree that there is conflicting info.

Depending on which issue of TM9-1276 you read, if the headspace is greater than 1.300" (per 1947 issue) or 1.298" (per 1953 issue) it is a candidate for one further test, the "Maximum Bolt" test (per the 1947) issue or the "Field Test Bolt" (per the 1953 issue) with known bolt face to locking lug dimension of 0.560". If the bolt closes on either of these further tests, the barrel is unserviceable (or perhaps the receiver is unserviceable).

If I am interpreting these TM's correctly, that means 1.298" - 1.300" is borderline unserviceable. I say this because the likelihood of finding a "long" bolt is remote considering that all bolts were machined to such tolerances to be interchangeable and that the maximum and minimum material condition of these tolerances will not result in a bolt/receiver combination being machined in a way to allow a long bolt to exist, unless it is out of specification.

The only other condition to consider is if the receiver locking lug surface is worn beyond specification, which would be a real bummer.

   
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richg072 View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote richg072 Quote  Post ReplyReply Direct Link To This Post Posted: Jan 26 2018 at 7:56pm
Sling, No unfortunately I don't have any gauges to measure MZ or TZ.  I have to bite the bullet and buy a set I guess.  I know when he checks H/S if there's any issues he usually goes through a couple bolts that he has just to be sure. I brought it in during the holidays and I know he was very busy and he had one of his guys do this one.  I'm not sure if checking H/S with numerous bolts is procedure for the entire shop or if this is just something he does personally, and if being busy numerous bolts would be checked.    
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