Strange effect of moving a cheek piece

Discussion in 'General Airgun Chat' started by Baltipal, Jan 16, 2009.

  1. Baltipal

    Baltipal New Member

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    I've come across something with the set up of my Pro Target that you may find interesting & I find frankly puzzling.
    Being a fat bloke with locked up hips meant that I required quite a high Hamster, my scope is mounted on high mounts & my cheek piece didn't have quite enough height to do the job so I recently got a shooting mate to knock up some higher posts & over Christmas got my Hamster reduced by 1/2 an inch & my cheek piece raised slightly.
    The first time I shot with the new set up I found I was missing low beyond 40 yards so a trip up to a Club with a permanent marked zero range showed me I needed 10 extra clicks for 45, 50 & 55 yards but I could not make any difference for 40 down to 20.
    Now, I'm having trouble trying to visualise the parabola of my trajectory as it now appears to have a step in it. 35 yards 3 clicks, 40 yards 10 clicks, 45 yards 28 clicks, see what I mean? I can understand how my POI may change with seeing down the scope slightly differently but why doesn't it effect all ranges, why hasn't my zenith point at 25 yards shifted ?
    What do you think?
     
  2. RobF

    RobF Administrator Staff Member

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    1/4 or 1/8th moa.

    How accurately are you measuring the zenith? Could it be there is a shift, but it's smaller at closer ranges?

    Puzzling though.

    Perhaps there's a change in the gun's reaction on the shot.

    It's not uncommon to have these sort of steps... i've had them myself before, but try shooting paper from 25-55 and plotting them to the click...sometimes the steps can seem larger than they are or on paper they can be seen as a bad range... although 10 clicks is a hell of a jump... thats the sort of thing I used to see in cold temps, and i used to have to take it all the way back through the zenith... that said, if the shift was 4-5 clicks then i'd only see them perhaps after the zenith...

    funny coincidence that the steps i've heard about have always been around 40 yds... never found an explanation for it, and a remark and rezero of the ranges normally makes it dissapear...
     
  3. Baltipal

    Baltipal New Member

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    Well, shooting today in decidedly Autumnal rather than Wintery conditions, quite a bit warmer though very windy & my original clicks are relavant again, many targets missed HIGH till I clocked it.
    It was suggested to me that the problem was Scope temperature sensitivity so I'm out tomorrow to buy a thermometer.
     
  4. RobF

    RobF Administrator Staff Member

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  5. Baltipal

    Baltipal New Member

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    What model do you suggest Rob?
     
  6. RobF

    RobF Administrator Staff Member

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  7. Baltipal

    Baltipal New Member

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    Cheers Rob. I assume you mean the D10 version as that appears to be the right temp range?
     
  8. RobF

    RobF Administrator Staff Member

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    Oh, i got all 3 :D

    in fact I got about 2-3 sets of each as well... figured to make the most of the postage... haven't seen it top out, but seen it use all three ( and bottom out on the cold one -3... funnily enough at the same place, Newbury)

    Spare set's i've used on spare scopes, and the girlfriend.
     
  9. Baltipal

    Baltipal New Member

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    I ordered the -3 to 13 degree one, cheers Rob.:)
     
  10. Adam

    Adam Active Member

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    I got 4 for £1.99 from ebay.

    http://cgi.ebay.co.uk/Make-Baby-Chi...14&_trkparms=72:1301|66:2|65:12|39:1|240:1318

    27 down to 9 Celsius. I use one on the action of my HW100 as it's so temp sensitive. The temp blocks are 3 degrees apart but you can use the changes of colour to nail it down to 1 deg. Also this works to extend the range a little (so even with a 9 degree lowest display, you can tell fairly accurately down to 6. I wish I could find a single small strip that goes from about 24 to -5 though.
     
  11. HotShot

    HotShot Active Member

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    Where did you stick it on the girlfriend Rob? ;)
     

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