308 suddenly not grouping well?

Discussion in 'Big Stuff -- 6.5mm, 7mm, 30 Cal' started by MOA, Jun 30, 2018.

  1. MOA

    MOA

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    I have a 308 that the groups have suddenly opened up. The rifle went from being a consistent .5 MOA rifle to a 2 MOA rifle with no changes.

    The rifle is a FN SPR A1 stock except for beddes. It has 1200 rounds on the barrel, mostly 4064 with a 178 eld m. I switched to varget last year and have maybe 300 rounds of that through it.

    I took the rifle down and checked the bedding, torque, scope base and rings, pretty much everything i could think of.

    I always clean with foaming bore scrubber and then montana extreme. Always use a bore guide and patches after a nylon brush and clean the chamber with a brush and mope.

    Do you think its my cleaning regiment? Im trying to get access to a bore scope and ordered some bore paste. The only other thing i can think is my scope crapped out. Any ideas?
     
  2. gambleone

    gambleone Silver $$ Contributor

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    Nylon brush might not be cutting it. Think your on the right track with the bore paste though.
    I would try a brass brush also. Try this first before looking for a scope problem. imho.
     
  3. MOA

    MOA

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    I also try to keep cleaning to a minimum. I have some bronze brushes on order with the bore paste. Im kind of suspicious i may have carbon built up in the throat but i have no pressure signs.
     
  4. riflewoman

    riflewoman Gold $$ Contributor

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    A sudden opening of groups with bedding in good shape usually means the scope has packed up. If betting goes, the groups become large and there’s also a zero shift. If the barrel is shot out the groups get hollow with no zero shift. But a scope packing up is sudden and the rifle seems sick with no apparent illness. Replace the scope with a known good one.
     
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  5. Bart B.

    Bart B.

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    If the barrel was totally free floating before, the stock fore end may have warped enough to touch it. 1/16th inch clearance around bolt gun barrels helps.
     
  6. MOA

    MOA

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    The stock is not making any contact. The scope is a Bushnell HDMR 3.5-21. The groups are hollow but i dont think the barrel is done. As soon as i get my order in i will clean the crap out of it and test shoot it. I will also try switching scopes if that doesnt work.
     
  7. shoot4fun

    shoot4fun Gold $$ Contributor

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    My bet would be on either a scope going/gone bad or a nick in the crown. IIRC, the barrels on these are chrome lined. Worst case scenario would be that there is an issue with that. There were some of these rifles, the last to come from New Haven, that exhibited all sorts of man-made issues. Those ranged from the scope base holes drilled off center to barrels that were left outside to rust before chrome-line process. Yes, they plated over the rust and plating was indeed coming off. Don't ask me who told me this info but rest assured they did work for FN during the time of transition from New Haven to Columbia, SC.
     
  8. JBT

    JBT Gold $$ Contributor

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    Probably hard carbon in the throat.
     
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  9. MOA

    MOA

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    Well if its barrel related then FN will warranty it. Im going to find someone with a borescope and have them look into it.
     
  10. Down South

    Down South FTR Junkie Gold $$ Contributor

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    Thinking the same thing.
     
  11. Nature Boy

    Nature Boy

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    My FN SPR did what yours is doing at around 6k rounds.

    After ruling everything out I took it to my gunsmith to have him scope it as I thought the barrel may be shot out

    Turns out I had a lot of carbon and copper fouling.

    I learned 2 things that day

    1. Use Bore Tech products as they do a much better job than what I was using

    2. Get a bore scope because what you think is clean probably isn’t and you can only be sure if you can look in the bore and see

    After a weekend of cleaning my 1/2 MOA returned
     
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  12. MOA

    MOA

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    As soon as I can I plan to purchuse a lyman bore scope or I may give in and get one of the inexpensive ones that hooks to a phone. It actually lost accuracy last year about as many rounds between hard cleanings. I, admittedly stupidly, assumed that foaming it every 100 rounds and patching it out was working.
    If anyone in NE kansas has a vore scope maybe we can meet up and peak. But I have a match saurday and have to get this thing grouping again by then. Or I swap this scope onto my back up rifle and shoot it after making sure the scope isn't the issue.
     
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  13. #40Fan

    #40Fan

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    Do you have a brush for your cleaning rod? If so, push it through the barrel and start pulling it back like normal. Feel for a "harder to pull" spot. That'll be your carboned up area.
     
  14. MOA

    MOA

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    Yes i have several bronze brushes and nylon brushes. I will give this a try latter tonight.
     
  15. ebb

    ebb

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    I bet when the borescope shows you it is clean and no copper it will shoot right again. How ever Ive never looked through a bore with any thing but a hawkeye and knew more than when I started.
     
  16. #40Fan

    #40Fan

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    I don't know if having a bore scope is the best thing in the world. I recently acquired one and I am not sure if I am going to be cleaning to anal retentiveness or just good enough to keep the gun shooting well. I do know after looking down the barrel of some of my guns, that my previous cleaning regimen wasn't up to par. I am slowing working through various barrels/guns to find out if "looks pretty clean" is good enough versus "brand new clean". I'd rather not have to over clean if just enough is ok.
     
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  17. MOA

    MOA

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    So i did the brush trick and im pretty sure, without a actual scope, that it had some pretty solid carbon buildup. I got my Iosso today and went to town on it until the jag and patch went from end to end without hanging up. I will load up a few rounds later this week and give it another try at the range.
     
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  18. davidjoe

    davidjoe Skunkworks Gold $$ Contributor

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    ... Hard chromed hammer forged heavy barrel that should last into 5 figure round count. I’m curious to hear your solution, having this gun myself. I’m assuming that chrome lining isn’t adversely affected by those solvent choices. As often as you cleaned it, I can’t see how fouling of any type let alone a carbon ring, could build up.
     
  19. Nature Boy

    Nature Boy

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    Exactly my story as well. Thought I was getting it cleaned. I was sadly mistaken
     
  20. MOA

    MOA

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    I will report back as soon as i get a chance to shoot it. The presence of a tight spot in the at the end of the chamber was easily felt.

    ETA- Chrome plating as applied by fn has a very high resistence to the Ammonia in cleaners, a rc hardness or 64+ so a very high abrasion resistance so barring one of the rusted barrel plating failures i would say the chrome is at no risk.
     
    Last edited: Jul 4, 2018

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