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Thread: Turning a barrel contour down

  1. #1
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    Turning a barrel contour down

    If you don't want to flute it, can you just reduce the diameter all over ? Can people tell me what's involved and the pitfalls ?

    Would this be a technical job that you only entrust to a qualified professional gunsmith or can an average rifle fixer do it ?

    I'm thinking it would be quite expensive in time, needing removing the barrel, setting up in lathe, Precision turning, bead blast, recrown, rethread suppressor and new bushing and nut if that could be done ? Can/should you reduce the diameter around the chamber as well as the bore ?

    Has anyone got a quick formula to estimate the weight saved depending on initial and final diameters and length of barrel ?

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    Depending on the rifling type, it can supposedly alter the bore/groove diameter, particularly with button cut rifling which relies on the meat of the barrel to hold its form - reduce the thickness and in doing so you reduce the tension, and “relax” the tolerances. Supposedly.
    More meplat, more better.

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    yes it can be done but it is labor intensive specially the finishing, sand blasting cant always remove a deep file or tool mark.

    Having done a few, i d rather send back a barrel to a barrelmaker to recontour it than me doing it.
    Bagheera likes this.

  4. #4
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    Reducing barrel diameter is the best way to reduce weight. The job requires special techniques and tool shape to be done correctly, and then the barrel needs to be polished and blued. It is not a job for a handyman with a lathe, it requires an experienced hand. 2mm of the barrel diameter will reduce the weight 2-3 times more than deep fluting.

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    An FN mauser barrel I have obtained for project #2 has a funny little step in between the knox form and the main sporter part of the barrel. part of me would like to see it smoothed out, but the other say its far too much dicking around and I have to reprofile the stock to suit it anyway.
    it will probably look alright once done and throw people off. Is it a parker hale or an FN?

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    Quote Originally Posted by csmiffy View Post
    An FN mauser barrel I have obtained for project #2 has a funny little step in between the knox form and the main sporter part of the barrel. part of me would like to see it smoothed out, but the other say its far too much dicking around and I have to reprofile the stock to suit it anyway.
    it will probably look alright once done and throw people off. Is it a parker hale or an FN?
    Probably FN, Parker Hale have tapered barrels.

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    Your stepped mauser barrel is a military contour. the steps were designed to interrupt barrel resonance on firing .

    My belief is that Mr Mauser new far more about firearm design than I do so I am happy to use a stepped barrel.
    rewa likes this.
    Cats have nine lives-which makes them ideal for experimentation...

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    Quote Originally Posted by muzza View Post
    Your stepped mauser barrel is a military contour. the steps were designed to interrupt barrel resonance on firing .

    My belief is that Mr Mauser new far more about firearm design than I do so I am happy to use a stepped barrel.
    An interesting theory, but the real reason is to simplify quantity manufacturing without having to waste machine time taper turning. It is far simpler and faster to manufacture barrels in a series of parallel steps. That is the first step in preparing a barrel for profile turning, saving considerable time in the many fine cuts needed to taper turn a barrel without chatter or distortion.
    nor-west, Woody, norsk and 1 others like this.

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    I have read accounts by competition shooters describing having to fire in the order of 20 rounds after cleaning copper residues from barrels before reliable grouping returned. I have had a similar experience myself. Any comments on this?

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    Probably worth having a chat to Hugh Bradley @Bradley Barrels, he knows his stuff. I can speak for his work he's done 5 barrel jobs for me.

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    Quote Originally Posted by Woody View Post
    I have read accounts by competition shooters describing having to fire in the order of 20 rounds after cleaning copper residues from barrels before reliable grouping returned. I have had a similar experience myself. Any comments on this?
    Yes, that is a common thing. Barrels perform best when they are at a certain level of fouling which varies from gun to gun. It always takes freshly cleaned barrels a few shots (usually 2-3) to settle to consistent grouping. Once the fouling gets to a certain level it stays that way for a great many shots, giving a consistent friction loading on the bullet. Target shooters always fire a few fouling shots from a freshly cleaned barrel before shooting for score. From a hunting perspective, where sub MOA performance is not needed, then it is not much of a problem.
    Woody likes this.

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    Good response. I have found by using Kroil, the rate of copper buildup is reduced. Even after thorough decarboning until no further colour on rags, after leaving a light coating of kroil in the bbl, when next wiped a few days later , prior to shooting, the patch comes out black. Kroil must get under carbon even where other cleaners don't reach.

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    Quote Originally Posted by gundoc View Post
    An interesting theory, but the real reason is to simplify quantity manufacturing without having to waste machine time taper turning. It is far simpler and faster to manufacture barrels in a series of parallel steps. That is the first step in preparing a barrel for profile turning, saving considerable time in the many fine cuts needed to taper turn a barrel without chatter or distortion.
    I would go with the military concept a bit more if it wasn't a 270 unless it started as a blank for a military barrel. @gundoc I tend to go with the machining theory but would've though FN would've finished it off so to speak

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    Quote Originally Posted by csmiffy View Post
    I would go with the military concept a bit more if it wasn't a 270 unless it started as a blank for a military barrel. @gundoc I tend to go with the machining theory but would've though FN would've finished it off so to speak
    As Gundoc mentioned,its cheaper/easier to reduce the barrel diameter in steps rather than a taper.

    Your FN might well have been produced in the 50s/60s when the world market was flooded with surplus arms and the Rifle you have would have had to compete on Price with Lee Enfields and Mausers with cut down stocks and cheap scopes.
    "Sixty percent of the time,it works every time"

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    FN M98 sporting rifles were manufactured with stepped barrels in the 60's and 70's.
    csmiffy likes this.

 

 

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