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  1. #1
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    Default Time to change my barrel?

    I bought a custom 2nd hand rifle in 7x64 that has shot very well with a 120g Barnes TTSX, COL of 82.5mm. I have recently found that my favorite load is no longer grouping like it used to. Groups size has gone from sub MOA to 2MOA. The rifle was originally a Mauser 8x57, so there is not much space in the magazine to allow me to seat the bullets shallower than the SAAMI spec of 82.5 so that I can "chase the lands", to see if the problem is that the lands are eroded. Perhaps I can pull a few out a bit, and chamber them one at a time and see if they will group with a COL of 84mm? Although I'm not 100% sure what this will tell me? In the interim, I have loaded some 160g Speer cup and core bullets which seem to group better (back to 1 MOA) but I don't like the trajectory or terminal performance. I'm assuming that if my worn barrel theory is correct then it is the rounder ogive of the heavier bullet that reaches the lands sooner, or a larger bearing surface that works better in a worn barrel?

    What checks do you think I should be doing before I decide to write the barrel off? Bore scope it?

  2. #2
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    Default Re: Time to change my barrel?

    Againstthegrains - I can relate my mauser '98 in 7x64 also grouped 2 inch groups. I found no real benefit in chasing the lands, as the typical throat on a 7x64 is exceptionally long. To make a long story short, the rifle now consistently groups sub moa (with a pet load), having bedded the action. My mauser's action bolts are locked in place with a second bolt (unlike the newer models). I believe what happens over time is that the wooden stock crushes under the action bolts' torque, but is hidden from plain view in that one assumes the bolt's action bolts are tight, being locked. All you need is a micron or two of action movement in the stock, for grouping to fly (with very high BC) out of the window. You can see the post here http://www.gunsite.co.za/forums/show...656-7x64-query , if that helps.

  3. #3
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    Default Re: Time to change my barrel?

    Take the rifle to a reputable gunsmith and have him take a look with a bore scope, if the barrel is worn it can often be set back and re-chambered giving you a few hundred more accurate shots. I had this done twice with my .300 win mag (2 different barrels), both times groups shrank back to the original sub moa level from 2 - 3 moa.
    Before you do that though, clean all of the copper out of the barrel if you had not done that already. I have seen a few rifles fed with monolithics loose accuracy, when the barrel is fouled with copper, and then regaining accuracy when properly cleaned.

  4. #4
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    Default Re: Time to change my barrel?

    Quote Originally Posted by TStone View Post
    Before you do that though, clean all of the copper out of the barrel if you had not done that already. I have seen a few rifles fed with monolithics loose accuracy, when the barrel is fouled with copper, and then regaining accuracy when properly cleaned.
    ^^^

  5. #5
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    Default Re: Time to change my barrel?

    Did it happen suddenly or progressively? I know a guy whose rifle shot perfectly then suddenly no more, according to a gunsmith the barrel was shot out and it would cost R####. In the end it was a loose scope mount. Did you maybe try back to basics?

  6. #6
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    Default Re: Time to change my barrel?

    I've gone through hell and back with that rifle. The scope mounts gave me issues, so eventually I replaced them with a Picatinny rail. The stock has been rebedded until I got it 100%, and the screws which can work themselves loose have been made super tight, and have not budged since. Just when I thought I had finally sorted out all the nonsense, and I was shooting touching holes. I decided to do a whole lot of load development with a range of bullets that I got 2nd hand from someone. (about 60 shots) When i went back to my TTSX load, it had opened up. I have tried cleaning the barrel, with no improvement. Since the load with the heavier bullets is still shooting ok, i can't say it is the scope mounts or bedding issues, as this should affect all loads? Hence my original conclusion.

  7. #7
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    Default Re: Time to change my barrel?

    Quote Originally Posted by TStone View Post
    Before you do that though, clean all of the copper out of the barrel if you had not done that already. I have seen a few rifles fed with monolithics loose accuracy, when the barrel is fouled with copper, and then regaining accuracy when properly cleaned.
    I have a bottle of Hoppe's and M98. Any preference for these to remove copper?

  8. #8
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    Default Re: Time to change my barrel?

    Quote Originally Posted by Againstthegrains View Post
    I have a bottle of Hoppe's and M98. Any preference for these to remove copper?
    M98 works really well, it just takes many runs to work it's way through the various layers of copper.

  9. #9
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    Default Re: Time to change my barrel?

    Changing from one type of a bullet to another, without cleaning out all metal fouling, can cause accuracy to go out the window. M98 will work for copper removal. Starting with a clean barrel, it might take a few shots before the rifle return to its original accuracy.

  10. #10
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    Default Re: Time to change my barrel?

    Quote Originally Posted by TStone View Post
    Changing from one type of a bullet to another, without cleaning out all metal fouling, can cause accuracy to go out the window. M98 will work for copper removal. Starting with a clean barrel, it might take a few shots before the rifle return to its original accuracy.
    Experience!!!!! Wow!!! Will give it a go.

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