New build: powder burning on and above case shoulder

Discussion in 'Gunsmithing' started by str8shoot, Apr 18, 2011.

  1. str8shoot

    str8shoot Well-Known Member

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    I just got my 7mm rem mag back from the smith, where he trued the action and put on a new Mcgowen barrel. I loaded up some rounds in new Win brass and went to break in the new barrel.
    Upon firing I noticed the shoulders on my cases were blackened after firing. A few cases had six lines (from the six groove barrel) half way up the case body. At first I thought I wasn't getting the chamber dry after cleaning, but that wasn't it. After I fired all 21 rounds with many cleanings I had 21 cases all with black necks and shoulders. 5 or so had the lines up the case body.
    So I got home and measured up some cases with my headspace gauge. It wasn't too far off (.009 shorter) than my old fired rounds so I figured my head space was probably OK. I set up my fl die to bump the shoulders .001. This time I loaded up incremental charges to start load development. I thought maybe my break in rounds were a little under pressure in this rifle. All fired cases showed pretty much the same results as the new brass.
    Obviously I may need to talk to the smith that built this rifle but I thought I would run it by some of you guys first.
    I am very happy with the accuracy and the velocity of the rifle so far but I wonder if I am causing damage to my chamber or any thing else?
     
  2. ken snyder

    ken snyder Well-Known Member

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    WOW! half way down the case. Talk with your smitty. Not saying this is what happened. once I took a barrel out of the lathe and didn't get it back in true. I ended up with a larger chamber and the ream didn't like it at all and put chatter marks in the chamber which looked an awful lot like rifelings. Really looking fwd. to hearing whats going on with this one.
     

  3. mrbigtexan

    mrbigtexan Well-Known Member

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    i am very curious as well, first thought that came to my mind was not centered well in the lathe. please keep us informed.
     
  4. str8shoot

    str8shoot Well-Known Member

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    Ken you pretty much nailed it. When I cleaned off the shoulders, I could see the brass wasn't formed smooth. I shined a light down into my chamber, it of course looked as rough as my brass. So it went back to the smith last week. He said the reamer must have chattered. So he is setting it back one thread. I must say I'm a bit disappointed in my smith. I make mistakes too but, I don't see how you can ream out a chamber and not even look at it before you install the barrel. His brass from when he test fired must of looked just like mine. He is making it right but he said he would have it ready for me last Friday, when I went to pick it up it wasn't done. He said it will be done today, I'll call first before driving out there again.
     
  5. ken snyder

    ken snyder Well-Known Member

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    str8shoot, sometimes a fast burning powder and hotter primer can hide something like that. It can expand the neck fast enough that it will make a seal before the dirty gases have a chance to work their way down between the brass and chamber. p.s. glad to hear back from you and that the concern is being corrected.
     
  6. rscott5028

    rscott5028 Well-Known Member

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    Shame on the smith. And, good for you for catching it.

    How many guys would've gone multiple firings experiencing quirks before runing into big problems?
     
  7. str8shoot

    str8shoot Well-Known Member

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    Well I picked up my rifle yesterday from my smith. He said he set it back one thread and everything seemed to clean up. He gave me an apology and showed me his brass from his test fire. It looked good and clean. Took it to the range today and everything looked great. Did some load development and this thing really shoots! I'm glad he made it right and I am now very pleased with this rifle. After 22 shots at the range today that Mcgowen barrel had hardly any copper fouling at all.