EV mk4 problem ??

Discussion in 'Air Arms' started by 5teve L, Aug 26, 2013.

  1. 5teve L

    5teve L STOP ! HAMMER TIME !

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    Apr 16, 2009
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    Horsham, West Sussex.
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    The Oaks & Horsham hawks
    Bare with me on this, I'll try to give as many details as possible, without going into to much of an essay... :D

    A friend has an EV mk 4, it used to shoot spot on, then it started playing up, it went back to AA for a service & all was well according to them. Mate thought it was scope, tried another, then he stopped shooting as he thought it may be him & got annoyed... short story is, I tested it over the chrono, 4 fps difference at around 775fps with AA field, just as AA said, but.. it wasn't grouping very well at 25yds at all, it would shotgun a little & then stick a few right on top of each other, then go back to having flyers.
    I turned the rifle up to 785-790 to see if it made a difference & was getting cloverleaf groups with no flyers & the rifle seems alot better to shoot :confused:

    Not knowing anything about the EV, can this be the reg pressure set incorrectly for the rifle? (needs fine tuning) Or barrel harmonics ? Different BC for pellets effecting things ??

    Just wondered if anyone had any ideas as I am at a loss & so is he.

    ta
    Steve
     
  2. Gar73

    Gar73 Douchebag/Mook Identifier

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    I would do all the basics first.

    Check everything is tight and secure, scope, mounts barrel etc.
    Try a different scope
    Clean the barrel (try this first)
    Try a different batch or make of pellets
    Look for clipping

    I doubt the increase in velocity has made a difference. If its consistent on the chrono then I doubt that's the reason. If 10 pellets leave the barrel at 770fps to 780fps then the air being delivered is not the issue.
     
  3. TOOL

    TOOL Independent FT Pumper

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    Eliminate the easy stuff first, try pellets , they are all different and it's what suits the barrel as an individual that counts ! What might be mega in someone else's cannon might not suit another !.,

    4fps spread is mega

    Magic numbers is around 777 FPS with 8.4grains and 801 FPS with 7.9grains

    Sounds like pellets initially or is the barrel free floated ?

    On the EV under the stripper there's a locking grub that clamps onto windicator band , most consistent EV users shoot them free floated , take that off , remove the grub and file a myrtle off the band so you achieve a 2 - 3 mm gap .
     
  4. 5teve L

    5teve L STOP ! HAMMER TIME !

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    Thanks for the replies.. we have tried pretty much everything.. & yes the barrel is floated.
    Might try some different pellets as that is the only thing left to extensively test really, but it used to like aa 4.52.. i know they do differ from batch to batch but it wasn't really that fussy before. He cleans the barrel with a pull through after a few comps so it should be clean. It was really accurate, then something changed.
    It is 100% better running faster for sure.. but not as tight as it used to be.. will dig out some old jsbs for him i think.. poss try a different tin from another batch.
     
  5. sneaky rodent

    sneaky rodent top bombing

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    doncaster
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    its also werth trying different head sizes for the pellets i.e. 4.50 4.51 4.52 my dads ev use to throw a few flyers around every now and again an after asking a few people he dropped from 4.52s to 4.51s an it's gone back to been sweet.
     
  6. killen

    killen Senior Member

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    Location:
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    Grouping

    Agree with everything said, but this may be a problem I have seen on full bore rifles. You say the groups are poor below 25yds. What are they like at say 50 yds. Maybe they improve or should I say become what you would normally expect.
    It could be that not all the pellets have stabilised in the distance you are reporting and given a bit more distance they may. Upping the power may be exactly what was needed to ensure all the pellets have stabilised earlier. 7.9 g express may also be the answer.

    I had a .338 Lap Mag and at 100 and 300 yds, the groups were nothing to get excited about. At 600 yds they were much better.
    Maybe its the same effect......:confused:
     
  7. IOM

    IOM Member

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    Location:
    west yorks
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    Redfearns FTC
    I know this might sound daft but pull the barrel through the other way round (muzzle to breach) had similar problem and just could not believe the crap that came out anyway that cured it so give it a try ATB Hughie :confused:
     

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