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Thread: More questions on contouring

  1. #1
    Boolit Bub
    Join Date
    Mar 2013
    Callahan CA

    More questions on contouring

    The contour/chatter post, excellent responses and I'd like to ask further questions. Over the years, I've had a couple guys request that I turn the steps off Mauser barrels, which I did, following best practices with light cuts and modest tailstock pressure and a well adjusted steady rest. I don't think I bent any barrels from poor practices, yet both guys kind of gave me the stinkeye when they shot the new profile and told me they had lost some accuracy. One of the guys is a master reloader and well understands that he would need to deal with a different barrel harmonic after turning and both guys adjusted bedding.
    So, my long winded question, is this something that happens frequently when re-profiling? In both cases they were Mauser original barrels, and I don't know if these originals were heavily stressed in manufacture, or if I did something wrong or 'tis the nature of the beast. Thank you for sharing your experiences, Paul

  2. #2
    Boolit Grand Master

    M-Tecs's Avatar
    Join Date
    Apr 2008
    Generally that's the nature of the beast. That is more true of mass produced barrels than something like a Krieger that is double stress relieved. There is a reason that they recommend fluting an or profiling before rifling.

    Normally when you remove material from the OD the ID will increase inside due to stress relief. Barrel walking can become an issue also. On the other hand sometimes you have zero noticeable effects.
    2nd Amendment of the U.S. Constitution. - "A well regulated Militia, being necessary to the security of a free State, the right of the people to keep and bear Arms, shall not be infringed."

    "Before you argue with someone, ask yourself, is that person even mentally mature enough to grasp the concept of different perspectives? Because if not, there’s absolutely no point."

    – Amber Veal

  3. #3
    Boolit Master

    Winger Ed.'s Avatar
    Join Date
    May 2007
    Just outside Gun Barrel City, Texas

    Over the years, I've become less inclined to change something and try to re-invent the wheel.
    If I was going to rebarrel one of those, I'd get a aftermarket barrel from a source that had a good reputation for making them.

    For the originals, and how successful their design is:
    I'd presume they had it figured out, and 'all the King's men' & 'all the King's horses'
    really did know what they were doing when they arrived at the design,
    and then made a few million of them that have all stood up well to the test of time.

    And me hacking and chopping around in the garage changing it probably wasn't going to come out well.
    Last edited by Winger Ed.; 03-30-2020 at 05:34 PM.
    It wasn't playing the blame game, finding fault, and complaining about every little thing that made America great.
    It was God, guns, and guts.

    Never pick a fight with old people.
    If they don't think they can win it: They'll just kill you.

  4. #4
    Boolit Grand Master

    Join Date
    Mar 2013
    Northwest Ohio
    Several things change when contouring a barrel. a change in contour can and will change the stress patterns in the barrel affecting harmonics but also sizes in the bore. Localized changes may result in tight or loose spots. Another is if the bore isnt straight thru the barrels center then the wall thickness will vary turning smaller will make this more obvious. Lighter barrels are more likely to walk shots as they warm. Turning a contour may also create some work hardening in the blanks.

    Those old military barrels had a lot of stress in them from the manufacturing process, equipment of the time, and steels available. They were made fast and to specs more open than sporting rifles or target grade firearms. All of this has an effect on your results when re-contouring a barrel.

  5. #5
    Boolit Bub
    Join Date
    Mar 2013
    Callahan CA
    Well thanks fellas, everything you say, when I stop to think about it is absolutely true, intuitively. But, when a man from Gun Barrel City Texas chimes in....only the most imprudent fool would not heed his advice. Grin.
    As I think about this further, to shave off an ounce in the name of cosmetic appeal with a good chance of degrading the accuracy, it just doesn't make sense. My wife has a pair of cowboy boots that just kill her, yet she wears them because they look nice....just wrong.

  6. #6
    Boolit Master Jedman's Avatar
    Join Date
    Nov 2014
    NW OH Oak Openings Area
    I work a lot with major brand take off barrels and out of DOZENS of them I have yet to see even 1 where the bore is within .005 concentric to the OD. Many are .020 + when indicating the OD while the chamber and muzzle are between centers.
    I turn these into thick wall barrel liners and usually flip these end for end 3 - 4 times while turning the OD and each time re-indicate and reseting the steady rest.


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Abbreviations used in Reloading

BP Bronze Point IMR Improved Military Rifle PTD Pointed
BR Bench Rest M Magnum RN Round Nose
BT Boat Tail PL Power-Lokt SP Soft Point
C Compressed Charge PR Primer SPCL Soft Point "Core-Lokt"
HP Hollow Point PSPCL Pointed Soft Point "Core Lokt" C.O.L. Cartridge Overall Length
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LRN Lead Round Nose LWC Lead Wad Cutter LSWC Lead Semi Wad Cutter
GC Gas Check