Case head separation/barrel reuse question

Discussion in 'Technical Questions & Information' started by Nukalpiaq, Aug 4, 2007.

  1. Nukalpiaq

    Nukalpiaq New Member

    Mar 5, 2007
    I am considering building a rifle using a Winchester 70 Classic SS 300 Weatherby magnum action and instead of buying a custom barrel I am considering using a factory barrel from a Winchester 70 Classic SS 375 H&H, the owner said he removed the barrel from his action due to a case head separation. I would like to find out what I should be looking for when I inspect the barrel or should I have a gunsmith inspect it for me ?
    From my reading I found out that one of the main reasons for this type of problem is due to excessive headspace, basically the factory's chamber reamer may have been a little worn out when the rifle was manufactured. I also read that a barrel could be reused but it would need to be set back and rechambered to tighten the tolerances. Another reason I read about for case head separation could have been due to the lugs and seats being worn or issues with reloading the ammo. I am still making my inquiries, so the exact problem is yet to be determined. My question; Is the barrel still safe to use and does anyone have any experience with reusing a barrel like this before? Thanks
    Last edited: Aug 4, 2007
  2. LDBennett

    LDBennett Well-Known Member

    Dec 20, 2003
    Hesperia, CA
    There are several things tha cause case head seprations:

    Magnum cased ammo is head spaced on the belt of the case just above the rim. If the barrel was chambered for correct headspace there but the reamer a bit long, then the shoulder of the case near the mouth may be a long way from the chamber wall. This is common in belted magnum guns as that shoulder to bolt dimension is not a control dimension (the belt is). When the cartridge is fired the pressure expands the case into the chamber wall near the case mouth first, anchoring it and pushes the shoulder into the chamber wall making the case stretch for the back of the rim to meet the bolt. The area of case just in front of the belt get the brunt of the stretching and after as few as a couple of reloadings the case head seperates. So no belted magnum case should be expected to go more than one or two reloads, if you full resize them. The trick is to not full length resize, but only push the shoulder back a few thousandths after the first firing. That makes the case headspace on the shoulder, not the belt, and you can get several more reloads out of the brass. Perhaps this is the "reason" the previous owner was having case head seperations with the barrel ...... too many reloadings.

    When you rechamber a barrel you fix the headspace problem and eliminate case head sepration caused by incorrect chambering of the barrel. So fitting the barrel to your gun must include setting the barrel back (one thread pitch or more if the chamber is too deep) and re-chambering it. This is starting anew so you should not experience case head sepration if you consider the first paragraph above.

    Magnum cases have greater potential for case head seperation (see first paragraph). If a shooter tries to get too many reloads out of them the brass normally dies by case head seperations just above the belt. So watch the brass there for that potential and throw the brass away BEFORE it seperates!

    If the bore is OK and the chamber smooth on the proposed barrel (for re-chambering you have to use part of the original chamber) there is no reason to expect that the end result wil be bad, assuming the gunsmith does the job correctly.

    Last edited: Aug 5, 2007
  3. Nukalpiaq

    Nukalpiaq New Member

    Mar 5, 2007
    Thanks for providing some feedback, all your responses have helped me to better understand what case head separation actually involves and what may have been the root cause. Personally I have never had this happen to any of my cartridges since all I have shot to date are factory loads and I do not reload.
    A respondent from another forum addressed an earlier comment I made regarding the worn chamber reamer and excessive head space problem, he stated a worn chamber reamer would result in insufficient headspace, not excessive. This sounds logical and correct.
    The primary reason I wanted to use an original Winchester barrel is to preserve the identity of the rifle as a Winchester 70 Classic SS, additionally I thought I would be able to save a little time and money on the turn around. I am starting to see that there may be some precision barrel work involved in getting the correct head space and additionally to insure that the barrel lines up correctly for proper sight and extractor slot alignment.
    My main concern with using this barrel was safety, since I would be the one carrying the rifle in the field. Since most respondents agree that the barrel and chamber would not be damaged by a case head separation then I am convinced that the barrel will be safe to re-use. The owner has offered to have a gunsmith check it out before selling it to me, I will decide after I get the gunsmith’s report.

    Here is an excerpt from the owner's response to my inquiry regarding the cause of the case head separation.

    Quote: I'm convinced it was caused from weak/over-annealed brass. The load was a starting load for the bullet and powder combination...using rounds that I loaded for a trip a couple years prior. I pulled all the bullets in that batch and verified powder type and weight...all the gas and pressure came back through the action...There have been less than 100 rounds down this barrel.
    Last edited: Aug 7, 2007
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