sleeving barrells with carbon

Discussion in 'Hunter (HFT) & Field Target (FT)' started by vinny, Nov 28, 2015.

  1. vinny

    vinny WHFTA 2015 World Champion

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    Just so happens I found a lovely bit of carbon that slid on the barrel of my hft 500 like a glove , a little bit of fp10 aided the instal in case of any future damp ingress and it looked loveley , made sure I had a tiny amount of to and fro float , it all rotated relatively easy between finger and thumb ,
    Couldnt hit a damn thing so off to an indoor range to check everything out , long story short , totally ruined an accurate rifle , if you rotated the carbon 90 degrees it changed the poi drastically ,how can this happen ?
    Harmonics , I dunno , not versed in the finer points of this science , anyone any ideas
     
  2. NeilM

    NeilM Well-Known Member

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    You have upset the natural vibration of the barrel.

    You need to get Jon Harris onto this, as it is right up his street. I have seen pictures of two different FWB800X's where he has bonded carbon to the barrel. They look great and work.
     
  3. Ceathreamhnan

    Ceathreamhnan WHFTA Champion 2013

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    I had this problem in early 2013. It turned out the carbon sleeve was very slightly banana shaped. As you rotated it it would push the barrel in different directions (even though it felt free), or if it stayed in the same place, the different length of expansion in the sleeve versus the barrel produced a unpredictable zero shift due to temperature variation.
    That's why I shot the 2013 worlds with the barrel wrapped in electrical tape ;)

    If you roll the sleeve along a very flat surface like a kitchen worktop you should be able to see the runout as part of it goes up and down.
     
  4. vinny

    vinny WHFTA 2015 World Champion

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    I made sure it had a bit of sideways float, but really 2 mm of carbon walling that slipped on easily,influencing 14mm (minus bore)o quality hardened steel , I do find that hard to believe , but hey ho , I, m up for comments :confused:
     
  5. Ceathreamhnan

    Ceathreamhnan WHFTA Champion 2013

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    My aim point would shift round in a 5 mildot arc, I made a circular paper chart once I found out what it was ;)
     
  6. Knockedover

    Knockedover CSFTA Champ

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    I've shrouded a couple of guns now and always gone oversized on the tube, 20mm id on 16mm barrels, with a front and rear collar and both have been spot on. They've been fixed at the front collar but the rear has been free to move. My first was set up to tension the barrel when tightened and would shoot great but removal and refitting at a slightly different tension changed the zero. Leaving the back of it unfixed cured any shift and can be taken on and off with no shifting :)
     
  7. hmangphilly

    hmangphilly Not quite a full phil

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    Hardened steel barrel ? Are you sure ?
     
  8. vinny

    vinny WHFTA 2015 World Champion

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    Sort of did that with my 900, the oversize tubing fitted into the same recess at the block , I then fitted a rubber o ring halfway and at the stripper end, I can rotate that and have no issues , my 500 sleeve changes my poi only about 15 mm at 50 yds but I dont want anything .
    I think I, m gonna polish the inside till it drops on then check again , it needs sooo little pushing on its ridiculous ,once this is accomplished it can only be harmonics surely, who knows
     
  9. vinny

    vinny WHFTA 2015 World Champion

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    Well steel anyway , quality , people will debate :D
     
  10. Dave Ramshead

    Dave Ramshead England HFT Team squatter

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    Just added a carbon sleeve to the custom gun Vinny, not noticed any negatives like you have though. Mine is 14 mm ID, 16mm OD.
    I will take it to the indoor tomorrow and double check rotating doesn't alter poi.
     
  11. vinny

    vinny WHFTA 2015 World Champion

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    Good luck with that Dave , be interesting to hear your results , I, m still wondering about whats happened
     
  12. OUTCAST

    OUTCAST Member

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    What is it with putting a shroud on barrels .
    Have you not heard LESS IS MORE.
    the less crap you have interfearing with your gun the less you have to fuss about and mess with your head .
    Strip back float your barrel see how it shoots may need to tune the barrel I set the harmonics with a adjustable air stripper a bit of a faff but worth it.
    Make a gun shoot with the min of clutter it will only mess with your head :shot:
     
  13. DYNO DAVE

    DYNO DAVE Senior Member

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    Carbon shroud

    Hi vinnie make sure that it's not touching the breach if it is and is not been cut square when you turn it the high point will make it move as you turn it try and keep a small space between the should and the breach , hope this helps.
    Regards Dave
     
  14. vinny

    vinny WHFTA 2015 World Champion

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    Dave, I did make sure I had about half a mil of end float, and checked the carbon tube rollng across a sheet of glass , and to be fair had about a mil of bend , still, the interior of the carbon may have been undoutably different , dependent on how it was rolled and whether the resin was sucked out,
    I gave up in the end, cut the stripper back to od 18mm and fitted an oversize tube just
    Like the ftp , hopefully now sorted ,
    cheers for all your feedback guys
    (C, mon we all want a bit of bling afterall , dont we ?, gotta have a lame excuse when it all goes wrong :))
     
  15. Ceathreamhnan

    Ceathreamhnan WHFTA Champion 2013

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    The 1 mm of bend was the same in mine, I bet that's the problem.
     
  16. Yorkshiretea

    Yorkshiretea B Grade Bandit

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    Vinny, there's a slo-mo video on Youtube somewhere of how a PCP barrel vibrates on release of shot. May be worth finding as it's a lot more than I believed and could be the root of your problem. Short of that I'd speak to Jon Harris or John Gray as they've done loads of work on barrel harmonics. Good luck.
     
  17. Dave Ramshead

    Dave Ramshead England HFT Team squatter

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    Just back from the Indoor, zeroed at 40 as per usual, made sure the float I had built In to it was giving a gap at the breech end.
    Then rotated the shroud 180 degrees, moved the poi left by 25mm
    Put it back to the original position, back on zero.
    Took the carbon off, poi moved left and up.....lots!
    Left the carbon off and rezeroed. Pity really as it looked a nice addition.
     
  18. tugg

    tugg itchy trigger finger

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    just the extra weight of carbon is going to effect poi, on my ftp900 just by moving a non adjustable muzzle brake back 5mm on the end of the barrel made a difference ,as we know its all due to harmonics. It does make you wonder , you have 10m air rifles with weights to fine tune the barrel and we are putting double the energy through the barrel, should we need less weight ,more or the same to stabilize the barrel?
     
  19. vinny

    vinny WHFTA 2015 World Champion

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    Just goes to show, still at least it saved some of us a wasted trip and expense, gonna have to give my oversize one a test now, makes me think that a lot of those original tight ftp shrouds that you couldnt rotate were causing most poi miseries now as well
     
  20. Deleted member 4175

    Deleted member 4175 Non member

    im getting paranoid over my carbon shroud now just reading this :(
     

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