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Thread: Gradual decline in barrel accuracy

  1. #1
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    Gradual decline in barrel accuracy

    A gradual decline in a new barrels accuracy

    Have you ever had a new barrel installed by a competent rimfire gunsmith and had it shoot "lights out" in competition for several months? Then, shortly thereafter, experience a gradual decline in accuracy, using the same lot of great ammo that won many matches?

    I have personally experienced this on a least two barrels from different manufacturers. Also, several local club members have had new custom rifles built, that were extremely competitive in local matches at first ... then the dreaded gradual decline in accuracy. I can't speak for all the others, but I clean my barrel's bore regularly ... using caution, with bore guide and good quality rimfire bronze bristle brush and quality solvents like Rimfire Blend and Pro-Shot ... also use ISSO in the chamber when needed.

    Are there any answers to why a new barrels accuracy may slowly deteriorate over a relatively short period of time? John

    PS: One smith vaguely mentioned a glazing issue.

  2. #2
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    Get somebody with a bore scope to look at it. I'd suspect something in your cleaning.

  3. #3
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    Quote Originally Posted by tim View Post
    Get somebody with a bore scope to look at it. I'd suspect something in your cleaning.
    Tim: I own a bore scope and cannot detect a leading or fouling problem. Has anyone else experienced a gradual decline in accuracy? John

  4. #4
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    The other thing that it could be is that whatever you've been doing to break in and maintain the chamber might be too aggressive and it's changed. Typically barrels just don't fall off after a few months. Next I'd really check to see if something happend to your bedding or stock.

  5. #5
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    Quote Originally Posted by tim View Post
    The other thing that it could be is that whatever you've been doing to break in and maintain the chamber might be too aggressive and it's changed. Typically barrels just don't fall off after a few months. Next I'd really check to see if something happend to your bedding or stock.
    Seriously doubt that I did anything to change the chamber dimensions on two barrels, from different manufacturers These barrels were shooting great for three to four months ... then just gradual decline began after that.

    I spoke with a gentleman a while back, who laps rimfire barrels for a living (not BC). Something he said during the discussion, which is detrimental to rimfire accuracy, I suspect may be occurring ... after time. I will wait and see if others have something to share. John

  6. #6
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    Check Bore again

    If the bore gets too smooth, you lose the ability to properly lube the bore. A de-glazing may be in order.

  7. #7
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    Glazing?

    I haven't heard of glazing yet in the brief time I've been shooting RFBR. Could someone please explain it & then de-glazing?
    John, hope you figure it out!

    Keith

  8. #8
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    Tooooooo Smooth

    When a bore gets supper smooth, it loses it ability to retain lube from the bullet. That surface then must be roughed up so to speak, to help retain the lube. If you don't know how to do this, send the barrel back to your smith and have him do it. That is how several barrel mfgr's suggested.

  9. #9
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    What part of shooting a 22 lr target grade bullet with lube have to do with making a SS barrel smooth (glazed) or is it the over use of products such as ISSO. ?

  10. #10
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    Friction

    Friction and over cleaning. It's your gun, do what you must.

  11. #11
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    Quote Originally Posted by rkcal22 View Post
    What part of shooting a 22 lr target grade bullet with lube have to do with making a SS barrel smooth (glazed) or is it the over use of products such as ISSO. ?
    Contrary to some opinions, IOSSO is abrasive and it's possible to overdo it. The reason I mentioned this earlier to the OP is that some guys try and polish the hell out of their chambers with it until they have a compromised chamber. It takes very little to take a tenth or two of metal off and you now have an out of round chamber. Barrels simply do not fade in a couple months.

  12. #12
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    Changes!

    Glazing is something that occurs on cast iron - not likely to occur on steel. Anyway, as surfaces get very smooth they don't need a thick lubricant film. Roughing of new surfaces is probably done more to obtain a good fit, that is to establish parallel moving surfaces, than to hold a lubricant film. Parallel surfaces is something you really wouldn't need to establish between a bullet and barrel. There is very likely some deposits (lead, tin, copper, carbon,oxides, etc) forming on bore as more rounds are fired thru it but even considering these I doubt the change in accuracy is due to a change in friction between bullet and barrel.
    As time passes with a barrel there are many other changes taking place that I would suspect rather than "friction". For example, the SHAPE of the bore and crown, the ammo, the shooter himself, the gun itself, and even conditions!
    Hate to say it, but bench rest shooters often have trouble telling differences in variations that occur in their "testing" and changes that might be taking place in their equipment.

  13. #13
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    Hi Center22........I have had the same thing happen. When the rifle accuracy seems to fall off I would run some Iosso through them, and the rifles started shooting very well after that. I used a bore scope, and the barrels looked clean. I placed some Iosso on a nylon 7MM brush and go back and forth a few inches at a time till I get close to the muzzle, and bring it back to the breach end. It really does bring them back to life. Just be darn sure you get it all out before you start shooting again. Doug

  14. #14
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    Quote Originally Posted by pacecil View Post
    Glazing is something that occurs on cast iron - not likely to occur on steel. Anyway, as surfaces get very smooth they don't need a thick lubricant film. Roughing of new surfaces is probably done more to obtain a good fit, that is to establish parallel moving surfaces, than to hold a lubricant film. Parallel surfaces is something you really wouldn't need to establish between a bullet and barrel. There is very likely some deposits (lead, tin, copper, carbon,oxides, etc) forming on bore as more rounds are fired thru it but even considering these I doubt the change in accuracy is due to a change in friction between bullet and barrel.
    As time passes with a barrel there are many other changes taking place that I would suspect rather than "friction". For example, the SHAPE of the bore and crown, the ammo, the shooter himself, the gun itself, and even conditions!
    Hate to say it, but bench rest shooters often have trouble telling differences in variations that occur in their "testing" and changes that might be taking place in their equipment.
    Copper??? Tin??? Cecil did you wander over here by accident?

  15. #15
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    Hi Tim!

    I've been off this forum for a while but I'm happy to see you are still around. I'd forgotten you require an explanation for most things technical, As to your question about copper and tin: Tin is very important element found in bullet alloys, and then some 22 bullets have a copper coating, and may even have trace copper in the alloy. I know you probably consider your bullets are 100% pure lead in which case you won't have to worry about finding any metals but lead in the bore.
    I knew you would reply to my post but I thought, rather than the deposits, it would be about my comment about whether the guy starting this thread truly had a problem, or whether he was just misreading his data.

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