headspace question (yes, another one)

Discussion in 'Gunsmithing' started by Offgridkid, Jul 21, 2013.

  1. Offgridkid

    Offgridkid Member

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    Ok, sorry for this less than exciting topic, but I just can't seem to find the answer anywhere.

    Background: I have a full machine shop (metal working has been a hobby of mine for years). I have watched all of the key AGI videos, i have successfully blueprinted my action and have just received my first go no-go gauges. After reassembling my rem 700 (5R) i checked the headspace and find that the bolt closes very easily on the no go gauge. Before anyone asks I can say that i only had to take of a couple "thou" to get the action and bolt trued up, no biggy there, was pretty close to true as is. I have probably only fired 300 rounds through the rifle (bought new). I want to put a new thicker lug (already purchased) on it and that means pushing back the barrel (not sure of what the official name of the part that the existing lug sits on is called, but that is the area I am referring to). My question (finally right. . . .) is this, can i simply shorten the action side of the barrel a few thou at a time until my no-go gauge won't allow the bolt to close without reaming the barrel? I realize that there is a given depth between the outermost part of the barrel and the face that the bolt approaches, I can turn that down as well to keep that dimension as it is now. I was just hoping to not purchase a reamer if not needed and given that i need to shorten the headspace why would any reaming need to take place.

    I hope I explained this question well, if not, maybe someone could point me to a place that labels all of the surfaces of a bolt and barrel so I can use appropriate labels in explaining things

    thanks all
     
  2. Daveinjax

    Daveinjax Well-Known Member

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    Others can check me if I'm wrong but the few thousandths needed off the back and an equal amount off the shoulder. Not off the action. Also , you can rent reamers for a reasonable amount.
     

  3. J E Custom

    J E Custom Well-Known Member

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    Jul 29, 2004

    The proper way to head space is to set the shoulder of the barrel back. Don't remove any more of the action
    face than necessary to true it up.

    If you use the go gage, and place shims (I use brass) on the bolt face until the bolt face will just barely
    close then Mic. the thickness of the shims you will know how much to set the barrel back.

    You must allow for barrel make up and .001 to .003 head space.

    This can be done but you must make trial runs, making the barrel up, checking the Head space and removing
    the remaining barrel shoulder to achieve the proper head space without using a reamer.

    Note: be sure and remove the ejector before setting Head space because it can/will cause false readings
    for head space.

    Hope this helps

    J E CUSTOM
     
  4. Offgridkid

    Offgridkid Member

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    Thanks much for taking the time out to explain this, That is exactly what i was hoping to hear, thanks much !!. If i implied that i wanted to do anything with the action then it was just me going a poor job of "splain'n" things.

    The action was "trued" on my lathe and that process took a couple thou off. The one question I have, I am not exactly sure what this part of the barrel is called, It is the part that is near the barrel hole that the bullet would first clear that the bolt face would be close to touching when the bolt is closed. . .just don't know the name of the flat part. My question, i assume that i have to turn down that "face" as much as I turn down the outer shoulder to keep the lip between this "face" and the outer shoulder a constant (it's currently 0.700")

    is that right? Is that what Daveinjax meant by "few thousandths needed off the back and an equal amount off the shoulder"

    is the flat part I am referring to the "back"?

    thanks again guys

    John
     
  5. Daveinjax

    Daveinjax Well-Known Member

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    Honestly , I know nothing. I have a crude understanding and thats it. Listen to the professionals. I confuse myself when looking at these things so I can't give advise.
     
  6. lazylabs

    lazylabs Well-Known Member

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    Your talking about the counter bore for the bolt to fit into.....

    Take the action and stand it upright in a vice, take the bolt with ejector and pin/spring/cocking piece removed. Make a drawing that lets you record the distance from:

    action face to front of bolt lung while locked up
    action face to very end of the bolt
    action face to the face of the bolt
    bolt diameter
    counter bore diameter
    front of bolt to front of bolt lug

    subtrace your desired clearance .005-010 depending on what you want

    add the thickness of your recoil lug and you get all measurements you need to reference when the barrel is in the lathe.

    If you add/subtract just right you will get the distance from the end of the barrel to your go gague on a 700 it usually ends up being a few thou plus or minus depending on how you did your blueprinting

    I am really just saying, make a little sketch, write down all the numbers and give it a few minutes to settle into your brain before you start cutting things to pieces, that's just my method......
     
  7. J E Custom

    J E Custom Well-Known Member

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    Re: head space question (yes, another one)

    The back of the barrel tenon is called the breach face. The recess on the back of the barrel tenon on some actions is called the bolt recess.(Some actions have a flat breach face like the Savage).

    Both the barrel shoulder and the bolt recess or the breach end need to be set back. the barrel can be
    set back until the head space is correct as long as the bolt recess is .007 to .010 off the bolt and the
    OD of the recess is .005 to .010 larger than the bolt nose.

    J E CUSTOM
     
  8. Offgridkid

    Offgridkid Member

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    thanks much for the help guys. The new issue I have is my barrel will not stick out of the back of my lathe (where I install my spider) while still being held in my 4-jaw chuck, its a 20" barrel, just didn't think of that until now. I have a steady rest but it has brass feelers and not roller bearings, I am afraid I will mar the SS barrel if I use it to hold the barrel. My thinking was to use a lathe dog and dead center on the end of the barrel while turning the threaded end (action end) down. Does anyone have any experience with this issue? Any thoughts on how to hold the barrel? I do thing the 4 jaw chuck may hold it but i am unable to make both ends of the barrel centered while on end is not sticking out. . . .can't indicate it if it's hidden in the lathe :-(

    so far, without being able to dial in the thin end of the barrel I can get the fat (threaded end) end of the barrel to a couple of tenths' and the face of the shoulder to with in a half a thou, I do see some slight wobble in the thin end of the barrel while the lathe is running (slowly) but imagine that with the measurements I have I should be good to go, just don't like the thought of not dialing in both ends

    So,
    1. go for it as is with a few inches sticking out of 4 jaw chuck
    2. try dog and steady rest (marring concerns there)
    3. other suggestion from you good folks?

    thoughts?

    again, thanks to all!!!
     
  9. bigngreen

    bigngreen Well-Known Member

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  10. lazylabs

    lazylabs Well-Known Member

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    Put it in your steady rest.......... you don't need rollers to chamber in. It's been done a million times and will still get a chamber better than factory.