What am I looking at??

Discussion in 'Gunsmithing' started by frostop, Oct 12, 2018.

  1. frostop

    frostop Well-Known Member

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    IMG110101-000343F.JPG IMG110101-000220F.JPG

    What I am wondering about is the apparent pitting in the photo on the right.
    This barrel was taken off of a rifle that I had built years ago, .338 Jamison.
    I recently purchase a borescope and the pictures are of this barrel.
     
  2. cohunt

    cohunt Well-Known Member

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    Looks like tool chatter marks to me, but I'm definately not a pro
     
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  3. yoteslayer

    yoteslayer Well-Known Member

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    Not sure but looks a lot like fire cracking what barrel mfg and how many rounds
     
  4. BallisticsGuy

    BallisticsGuy Well-Known Member

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    This. Circumferential grooves are tool marks. It'll probably make it take a while to get copper equilibrium but no worse than most off the shelf rifles. Good bore scope pic quality!
     
  5. Hand Skills

    Hand Skills Well-Known Member

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    Looks like galling to me. Galling is defined as adhesive wear. In truth it's likely a combination or abrasive wear and adhesive wear.

    Very much exacerbated by the machining marks left behind by tooling.

    The mechanism at play here is material getting stuck in the machining marks and taking barrel steel with it when it leaves. Under intense heat and pressure it's not an easy thing to model, but that's what happens in a rifle barrel.

    Lapping is a very effective means of reducing such tool marks, which in turn reduces fouling. It also can reduce the fouling shots required to reach the equilibrium @BallisticsGuy mentioned.

    I understand you're asking about the pitting, does that answer your question?
     
  6. frostop

    frostop Well-Known Member

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    Yes, and I was a little surprised to see machine marks like that.

    My other thought is that I used to use Sweets until I learned here on these forums that it was not recommended by some. Was wondering maybe some of the Sweets was not removed by dry patches and left in the machine marks and possibly initiating the pitting.

    Thank you all for the replies

    By the way the rifle this barrel was on has since gotten a 270wsm barrel(pacnor) that shoots very well!


    Gary
     
  7. frostop

    frostop Well-Known Member

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    If memory serves it was a douglas barrel but I am not positive.
    Actually I did not keep exact round count but not a lot-maybe 200?

    Lyman borescope
     
  8. Hand Skills

    Hand Skills Well-Known Member

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    By the two pictures it appears pitting is localized to the lands only. If you are seeing pitting in the grooves also, maybe a solvent has an effect. But on only the lands I don't think so.
     
  9. frostop

    frostop Well-Known Member

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    Ok, good information.

    I recently got the bore scope and have taken a look at most of my barrels.
    This particular barrel is the worst of the bunch which is surprising to me since this was suppose to be a custom barrel at the time. The pacnor for example doesn't have near the machine marks that this one does.

    Anyway just asked for my own information, probably not going to use this barrel any longer! Thanks again for all the replies!!

    Gary
     
  10. BallisticsGuy

    BallisticsGuy Well-Known Member

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    Why not keep using it? The lands are still sharp and there's no alligator skin. I would assume the throat is in similarly good condition. If the gun still shoots well, use it till it stops shooting well.

    Many of my students have asked me if they should get a borescope. I always tell them no. Anything they learn from looking in the pipe is unlikely to be well understood by non-experts and will only cause them to needlessly second guess themselves.
     
  11. B23

    B23 Well-Known Member

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    That's about how most factory barrels look when they're brand new, I'm a little surprised a custom barrel looks that bad though as they nearly always look much better than that.
     
  12. J E Custom

    J E Custom Well-Known Member

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    What you are looking at is a very poor Quality barrel !!!
    The annular marks are from the drilling process. It was bored to large for the reaming (If reamed) to remove it. Reaming is a very important part of the rifling process and is done to true up the drilled hole and size it for rifling.

    It also looks like the rifling process was not proper to get the annular drill marks off the top of the lands. The top of the lands should be smooth and free of any machine marks. in addition to all of the problems with the bore, The billet had some problems as well that caused Delamination. (the missing square chunks are not indicative of piting) this normally occurs when a sufficient amount of the billet is not removed before forming/rolling and the billet still has some slag
    or defects in it and when rolled they leave cold joints/lamination's.

    Attached is a link to a barrel makers video inspection and what the bore should look like when finished. that may give you an idea of what a bore should look like if done correctly.
    http://riflebarrels.com/video-inspection-machine/

    This looks like a buttoned rifle barrel Because of the lack of machine marks on the edges of the lands where the barrel material is forged into shape and size, and with the improper bore size there was not enough material to displace the defects. This can also occur in a cut rifled barrel if the proper process is not used. I have a brand new cut rifled barrel that has some major problems and has been rejected for use.

    Chances are that you cant see any defects with a bore lite, but when you look with a good bore scope, what appears to be fine, suddenly
    is shockingly bad.

    J E CUSTOM
     
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  13. frostop

    frostop Well-Known Member

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    Thanks again for the replies

    At this point I think what I am going to do is use this barrel to do a test chamber and maybe actually shoot it a bit. Than possibly purchase a new barrel and chamber it.

    Thanks again

    Gary
     
  14. B23

    B23 Well-Known Member

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    It won't surprise me if it shoots really well for you. The barrels on my CZ 527's look about like that and they still shoot amazingly well.