Track down the reason for a POI shift

Discussion in 'Steyr' started by DaveRob, Jul 26, 2018.

  1. luddite

    luddite I Love HFT

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    808
    Location:
    Upper Buggersdale, Leeds
    I clean my Steyr barrels about one every two years, I've never experienced POI change, ever.
    Two of them are barley twist and two of them aren't.
    Stop prattling about with barrels.
    If I ever, and I have on other guns, find a POI change it was probably down to impact to the barrel or scope.
    Try checking all bolts for tightness before exploring other causes .
     
  2. North Ox Nath

    North Ox Nath New Member

    Joined:
    Aug 30, 2018
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    Location:
    Oxfordshire
    Club:
    NOFTC
    Thank you for your suggestions gents. Definitely have a few things to check and try out.
     
  3. DaveRob

    DaveRob Member

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    Nov 13, 2017
    Messages:
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    Location:
    Durham
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    York FT Club
    Soooo..... having be released from work duties I have finally got round to doing something about floating my barrel on the Challenge.... but before I strip everything down I thought Id do that shot string over the chrono. I filled it to 200 bar and ran 30 shots just as it was results were, in ft/sec with 8.4 AA diablo field

    1 shot every 25 seconds, values generated by my combro

    791
    791
    771
    785
    792
    796
    791
    785
    781
    785
    789
    789
    786
    787
    791
    792
    795
    787
    793
    794
    783
    784
    789
    797
    783
    789
    790
    786
    785
    788
    781

    I prefer to run a bit slower around 770 just to be totally safe so I backed the power down a shade and ran a few pellets then recorded another 20 shot string

    772
    770
    778
    773
    776
    776
    780
    785
    780
    782
    777
    779
    781
    782
    783
    790
    784
    775
    782
    785

    By this time Id hit about 100Bar so stopped

    My question is ..... does the above look correct or suggest any issues that may want looking at while I have the rifle in bits. Personally it looks like their is some instability as the spread in both is between 15 and 20 ft/sec.

    Thanks
    \
    DaveR
     
  4. nemesis

    nemesis 55yrd standing expert, or was it 8 or 9?

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    1,256
    Location:
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    Check to see if roller bearings are scuffing the hammer shaft
     
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  5. RobF

    RobF Administrator Staff Member

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    Location:
    New Forest, Hampshire
    Club:
    Parkstone Gun Club, South Dorset FTC, Southampton Buccaneers
    I’d say it needs a service.
     
  6. luddite

    luddite I Love HFT

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    I'd say that was normal for a Steyr, they seem to knock targets down quite well though. :D
     
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  7. gold682

    gold682 Member

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    Location:
    Enfield
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    Springfield
    Dave,

    Did you float your barrel?

    Paul
     
  8. Lavant_Lad

    Lavant_Lad Old Git.

    Joined:
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    Location:
    Newcastle Upon Tyne UK.
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    Redfearns FTC. & Steve Smith's Dinnington.
    Its not bad for a Steyr 15fps spread , presume with pellets straight out of the tin. Could be improved if you weigh some out to a close tolerance.
    I would not lose any sleep over your findings, at 45 yards its not going to make any difference with a Steyr.
     
  9. DaveRob

    DaveRob Member

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    Location:
    Durham
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    York FT Club
    Hi Paul

    Yes I have floated the barrel, the general concencus was I should bore the chassis to relieve the barrel. but due to the shape of the challenge chassis and the angles that it has at the bore points this is WAYYYYY more difficult than it seems. You would have to set up to effectively line bore it between centers either mounting the chassis on the cross slide of a lathe and setting a boring bar between centres, or creating a lengthy set up on the mill. Just using a reamer is out as it wouldn't bore straight due to the approach angles. mainly in the centre 2 positions This is all possible BUT the rifle can not be put back to original without purchasing a new chassis....... so I turned the barrel in the local areas to the chassis, SHOCK , even this isn't easy as I had to set it up in a collet chuck with a steady. One thing that surprised me was the barrel wasn't perfectly straight from the start. Put it this way, if one of my cars cranks had that much deflection I would bin it.... and Ive binned cranks with less than 4 thou run out.

    Their is visible... but small... clearance between the chassis and the barrel now at the points that it passes through the chassis, and if I want to put it back all it costs me is the price of a new barrel. Last weekend was the first time I have had chance to take it out and try it.... And its much MUCH better than me. At 55 yards it consistently knocked over 25mm targets. From morning through the afternoon.. so from about 9-18 degrees without even a hint of drifting, its also quite astheticly pleasing as I now have a matt black barrel with 3 silver bands. Some will decry that it isn't the BEST solution..... but it WORKS, it looks good and I can revert the rifle back to original for very low comparative cost..... but mainly it worked.

    DaveR
     
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