The plumb line at Pete's farm

Discussion in 'General Airgun Chat' started by Dr_C, Sep 25, 2015.

  1. Dr_C

    Dr_C Member

    Joined:
    Sep 12, 2014
    Messages:
    51
    Location:
    Cambridge
    Club:
    Cambridge HFT
    Last Tuesday I paid my weekly visit to the farm to check my aimpoints and do some plinking. First things first: level the scope. Drop the plumb line, attach the level to the dovetail, turn the mag on the scope down, get everything lined up.

    Sort my aimpoints, everything's looking good at the far end, pulling a little bit right at 8&10 yards, but still workable.

    Gun back in the bag, back up the M11 to home, putting the gun back in the safe, what's this? The scope is visibly canted.

    It's not the first time this has happened, I'm wondering if anyone else has had this problem? Is there some kind of local gravitational distortion?

    C.
     
  2. Sharpe

    Sharpe Semper fidelis

    Joined:
    Jun 25, 2009
    Messages:
    1,328
    Location:
    Waltham Abbey
    Club:
    Maldon
    It's a little known fact, there is a small "black hole" at Pete's, that has torn a hole in the space/time continuum. This may well be the cause of your problem.
    Try going on a Sunday, when the black hole is closed, to meet current EU regulations!
    Hope this helps!
     
  3. Tench

    Tench WHFTA World Champion 2016.

    Joined:
    Sep 23, 2009
    Messages:
    1,719
    Location:
    derby
    Either that or call a property surveyor, your house may have subsided!!
     
  4. RobF

    RobF Administrator Staff Member

    Joined:
    Mar 4, 2010
    Messages:
    12,194
    Location:
    Poole, Dorset
    Club:
    Parkstone Gun Club, South Dorset FTC, Southampton Buccaneers
    You of course checked the gun was level first? Otherwise all you did was rotate the scope so it's level then clamp it up... the gun could have been at 45 degrees... you then get gun straight or what you think is straight, scope looks off.

    Plumb or plum? :D
     
  5. Dr_C

    Dr_C Member

    Joined:
    Sep 12, 2014
    Messages:
    51
    Location:
    Cambridge
    Club:
    Cambridge HFT
    I have one of those little Hawke bubble levels that clamps on to the dovetail, so the gun and stock should be vertical.
    I've seen others do it by eye, and the person I shoot with regularly does it empirically, shooting long and short until crossover goes away. Is there any other way?

    It's plumb from the latin 'plumbum' meaning lead, for the weight on the end of the string.

    C.
     
  6. Knockedover

    Knockedover CSFTA Champ

    Joined:
    Apr 6, 2009
    Messages:
    991
    Location:
    Nr Portsmouth,Hampshire
    Dovetail mount ones are very rarely level I've modified several so they actually clamp up level. Best bet is a slim pocket level or a single bubble that's known to be level placed across the breech or dovetails.
     
  7. Akita

    Akita Member

    Joined:
    Sep 26, 2013
    Messages:
    193
    Location:
    UK
    Club:
    Greyhound & Purley Chase
    Theres a good chance this is the reason, the levels not square to the dovetail/action.

    Just take your time and do it by eye leveling the gun.
     
  8. SteveC200

    SteveC200 Active Member

    Joined:
    Jan 19, 2012
    Messages:
    406
    Location:
    Colchester
    Club:
    Iceni Marksmen
  9. Dr_C

    Dr_C Member

    Joined:
    Sep 12, 2014
    Messages:
    51
    Location:
    Cambridge
    Club:
    Cambridge HFT
    OK, so the consensus is that I need to get a better level. I did try my 3ft brickies level but it was a job balancing it on top of the mounts.

    Thank you all for your help.

    C.
     
  10. Tench

    Tench WHFTA World Champion 2016.

    Joined:
    Sep 23, 2009
    Messages:
    1,719
    Location:
    derby
    Or you could just use your phone, if it has a flat back lay it across the rail under the scope, many have a bubble level app and most have an accelerometer which an app can use.
     
  11. Sharpe

    Sharpe Semper fidelis

    Joined:
    Jun 25, 2009
    Messages:
    1,328
    Location:
    Waltham Abbey
    Club:
    Maldon
    Plumb or plum? :D[/QUOTE]

    I believe your little quip was missed Rob :)
     
  12. KeithW

    KeithW Barn door? Where?

    Joined:
    Feb 10, 2012
    Messages:
    256
    Location:
    Nr Sandy, Beds
    Club:
    Cambridge
    I found the Hawke level to be very poor, screw not long enough. The Sportsmatch one is massively superior. But I've also used the bubble from a broken level, laid across the action in suitable rifles
     
  13. RobF

    RobF Administrator Staff Member

    Joined:
    Mar 4, 2010
    Messages:
    12,194
    Location:
    Poole, Dorset
    Club:
    Parkstone Gun Club, South Dorset FTC, Southampton Buccaneers
    Perhaps yes. There's a type out there sold under a number of brands which either has an Allen bolt or knurled nutt that tightens it down. About 0.5mm from tight mine kicks out of true.

    I use a squared photography level on the guns that have flat sections. On guns that don't it's a pain. Scope mounts can be out as well on the rails. It's not easy and it can take a variety of techniques to get a gun level and plumbed before putting a scope on. Trouble is the eye is not the best judge.
     
  14. FPoole

    FPoole Member

    Joined:
    Dec 10, 2011
    Messages:
    110
    Location:
    Plant City, FL USA
    I do it by eye first. I then place a target paper out at 15 yards or so. I set it up level and take a longer level and draw a perfectly vertical line with a sharpie. I shoot at the line keeping my vertical cross hair on the line and adjust until I'm hitting the line. I then run the elevation up a turn or two and shoot at the line followed by turning down the elevation a turn or two past the original setting. All the shots should be on the line. If the scope is not plumb, the groups will fall to one side with the high shots and to the other with the low shots. The hard part is remembering which way to rotate the scope to make the correction. I have found that with BKL mounts, I can just set them on a level surface and mount the scope with a small level on the turret cap. I shoot a gun (TX200) with no flat spot for a level and this method gets me very close.
     
  15. Adam

    Adam Active Member

    Joined:
    Jan 5, 2009
    Messages:
    918
    Location:
    Leeds
    Club:
    Redfearns & the UBC
    I use one of these www.riflescopelevel.com/vertical_retical_instrument.html
    I imported from Brownells in the States a few years ago. As long as your scope objective is round and the top of your barrel/action just below it is also round, it will centre itself. You clamp the rifle. Then with the instrument sat on top of your action and the top bit resting on the scope bell, get the rifle so the bubble shows level, then you look through the scope (the slot allows enough light in) at a plumb line and adjust your scope so the reticle is vertical.

    Sometimes when I'm lazy though I just do it by eye and seem to get pretty close. I don't look for "level" as it's too easy to confuse yourself, I just look for the bottom vertical crosshair to seem to bisect the action beneath the scope.
     
  16. RobF

    RobF Administrator Staff Member

    Joined:
    Mar 4, 2010
    Messages:
    12,194
    Location:
    Poole, Dorset
    Club:
    Parkstone Gun Club, South Dorset FTC, Southampton Buccaneers
    That looks neat.
     
  17. Dr_C

    Dr_C Member

    Joined:
    Sep 12, 2014
    Messages:
    51
    Location:
    Cambridge
    Club:
    Cambridge HFT
    So I went back last night

    With a variety of small levels and I discovered a couple of things:

    1) The Hawke level didn't concur with any of the other levels. The ability to clamp onto dovetails is nice but it's not a lot of use if it flips up to one side when you tighten it the teensiest bit.

    2) A simple acrylic level resting on the top surface of the action worked best (A pressie from the generous S. Edmonson).

    3) The tops of the mounts aren't usefully level

    4) Some twit had set the place on fire!

    Reckon I'm all dialled in now, no crossover, ringing the bell consistently, not veering off to one side for the short ones.
    Thank you all for your suggestions.

    C.
     
  18. RobF

    RobF Administrator Staff Member

    Joined:
    Mar 4, 2010
    Messages:
    12,194
    Location:
    Poole, Dorset
    Club:
    Parkstone Gun Club, South Dorset FTC, Southampton Buccaneers
    Nice.

    Just out of interest, do you know which way it was going and which way you had to rotate? I've got a gun that's hard to square up and I think this is my problem.
     
  19. Dr_C

    Dr_C Member

    Joined:
    Sep 12, 2014
    Messages:
    51
    Location:
    Cambridge
    Club:
    Cambridge HFT
    The scope was canted anticlockwise

    And that made it go right for the short ones and left on the long ones.

    C.

    Edit: Sorry clockwise, I'm an eejit.
     
    Last edited: Oct 1, 2015
  20. iShot

    iShot New Member

    Joined:
    Sep 7, 2015
    Messages:
    2
    Location:
    Wigan
    I don't understand it? Just buy an FTP 900 which has a level already fitted... :D
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice