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POI shift with silencer

Discussion in 'Anything Airgun Related' started by dom501, Dec 21, 2013.

  1. dom501

    dom501 Member

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    Hi Folks & Merry Christmas:)

    I know when you attach a moderator you tend to get a slight point of impact shift or grouping inconsistencies. But after zeroing my rifle at the 22yrd indoor range last night along with some pellet testing Bisley Magnums (4.52) came out on top.
    I'm currently using a Daystate Air Ranger .177 with a shortened shroud & Weihrauch silencer, and today went to the 38yrd outdoor range. I aimed at a spinner at about 37yrds (nothing).
    I didn't know where half of my shots were going until I aimed at a piece of timber at 37 yards. My POI was 2 mildots low on 16x mag (maybe 3". I re zero'd and was getting sub 1" groups after that. This is something I've never come across before. Is this a common problem?
    I have chrono'd the rifle with the silencer off but not with it on.

    Thanks again

    Dom
     
  2. Tripleteer

    Tripleteer Donator

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    Are your pellets clipping the top of your moderater???? Atb Paul.
     
  3. lilman2106

    lilman2106 Well-Known Member

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    i may be wrong and probably am, but if your zeroed at 22yrds using bis mags on 16x mag 37 yrds would be around 1.5 mildots hold over.

    hope this helps if im right.
     
  4. dom501

    dom501 Member

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    I've had a good look on the moderator and the mod screw adapter and there isn't any clipping. Just after submitting the post I chrono'd it and all shots are pretty consistent at 11.5 to 11.7 (702fps).
     
  5. paul81

    paul81 Engaging Member

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    such a high mag and nearly doubling your range from zero. sounds like you have a very normal pellet drop even for a .177 to me?

    when you re-zeroed what range did you use?
     
  6. dom501

    dom501 Member

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    I re zereo'd at a different range. Approx 37 (haven't got a range finder) yards where the pellets were dropping. After that I was getting sub 1" groups.
     
  7. cloverleaf

    cloverleaf Super Moderator Staff Member Mod/Admin

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    So in a nutshell, you zeroed at 37yds, fitted the mod and it was then going around 3" low..?

    Mods often lower the POI, however 3" sounds like a fair bit. I know the Daystate rifles have had some issues with shroud / mod adaptor misalignment, but if you're happy it's not clipping..

    You mention inch groups - the rifle should do better than this at this range - are they noticeably worse than with the mod removed?
     
  8. dom501

    dom501 Member

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    No... originally the rifle was zero'd with mod at 22yrds at 37 yrds these were hitting 3" low, so I re zerod the gun at 37yrds with mod and was getting groups under 1". I did this just to rule out clipping or anything like that. The grouping seems fine. It's just the drop from 22 to 37 yrds then again I didn't take into account the weight of the pellet.
     
  9. metalman

    metalman Big Poster

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    If you alter the mag after zeroing, anything apart from zero range will be out
     
  10. paul81

    paul81 Engaging Member

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    sounds like everything is normal mate, you just need to work out what is your ideal zero range and then shoot different ranges to find out your pellet drop. sorry if that was a bit suck eggy, but you rifle sounds ok.
     
  11. dom501

    dom501 Member

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    Yeah i think i started to panic a bit when I noticed the pellet drop, And thought that the rifle was inaccurate. The outdoor range mainly consists of spinners and odd things to plink at so you can't really see where the poi is.
    There are range markers though at 20, 30 and 38yds, thing is though the firing point is stepped so unless you have a range finder you don't know the exact range.
    What I have read elsewhere is because I've had the shroud shortened on my Air Ranger the mod may be acting as a muzzle weight. But all in all I'm just glad it's not affecting the grouping and the rifle is still accurate.

    Another thing I didn't take into account was the B.C. of the pellet. I'm used to using JSB Exact Express (7.87gn 802fps) as apposed to (Bisley Magnum 10.5gn 702fps)
     
    Last edited: Dec 22, 2013
  12. ambriel

    ambriel Engaging Member

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    If you're clipping the silencer then I'd expect there to be a visible mark left where the pellet left the end of it.
     
  13. Uriel

    Uriel Engaging Member

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    There are two factors at play here and they both affect the same thing.

    1- You have more weight on the end of your barrel. It is negligible but it's there nonetheless.

    2 - The moderator drastically changes the way that air leaves the end of the barrel.

    Both of these have an effect on your gun's recoil (however slight it may be, and however much it gets damped, there's got to be an equal and opposite reaction to the pellet being fired - physics says so) and this affects the point of impact.

    I have had exactly the same issue with a Falcon FN8 and an AA S410. Using different moderators would affect the POI differently, too.
     
  14. RichieRich

    RichieRich Ping!

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    A silencer will cause POI drop, just needs re-zeroed and all will be fine. Magnification however, will cause a different poi on your mildots. Find a suitable zoom and stick to it.

    If your POI is all over the place, then your pellets are clipping the silencer on the way out.
     
  15. oaktree

    oaktree Member

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    It's due to the bisley mags dom. I tried them a few years ago just out of interest. Made the drop on my .177 more like shooting .22
     
  16. craigfishin

    craigfishin Donator

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    Sounds reasonably normal to me , I'm zero' at 35 so at 50 (the same distance change as you ) I would need to allow a Mildot holdover with lighter pellets than you using so with the heavier pellets 2 Mildot holdover sounds about right
     
    Last edited: Dec 24, 2013

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