Inclined shot point of aim question

Discussion in 'Hunter (HFT) & Field Target (FT)' started by Sundance, Oct 13, 2014.

  1. Sundance

    Sundance Bush Cavity

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    Has anyone worked out a method to determine point of aim on incline shots?

    Thanks
     
  2. Brian.Samson

    Brian.Samson Allowed in Sales Staff Member

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    Rule of 15's

    If it's less than 15 yards OR less than 15 degrees - treat it the same as you would for a level shot.

    If it's more than 15 yards AND more than 15 degrees - aim low but still inside kill.


    That will work for 99.9% of the shots you're ever likely to see in the UK and for the times where it won't work, knowing where to aim won't be the biggest problem, it'll be figuring out how to keep your crosshairs still that's the biggest problem.

    (as a footnote - if you're using a springer, all bets are off)
     
  3. sven

    sven Member

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    When the target is in a tree or on a pole I rangefind on the foot of the tree/pole and use that range to set the scope.

    In mountainous terrain with targets up on a slope this won't work. But for targets in a valley you might find a tree at the same distance and that is high enough to reach the horizontal plane from where you're shooting from.

    The reason to aim low (and to rangefind only in the horizontal plane) at high or low targets is that gravity only pulls the pellet down over the horizontal distance and not over the inclined path of the pellet which is longer.
     
  4. NJR 100

    NJR 100 Because I`m AWESIME !!

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    Will take you Down the Bowl and show you our angled practice shooting area Thursday Simon.
     
    Last edited: Oct 13, 2014
  5. DEAN C.

    DEAN C. Steyr Convert

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    Thats the old riflemans rule and works up to about 20/30 degrees at reasonable distances IMHO, thereafter you are onto Brians 15 + rule. ( I think that makes sense).

    As Brian was intimating, the steeper the angle and/or distance the more you have to allow, and the riflemans rule (which I do use up to about 25 degrees or 25 yards) and then after that add a bit, not really scientific in my case, but I seem to be getting better at the angled shots. Emley Moor love to throw a few at us! (thanks Chris/Trev).:rolleyes: and Anston and their tree targets (thanks Calps).:rolleyes:

    The Emley club banking for one example, makes for some excellent and testing angled shots where the riflemans rule does not work, 45 degrees down at 45 yards tests your nerve a little. I think that was 45 yards on the horizontal!!! Some seem to lift half a mildot or more from the banking down at distance.
     
    Last edited: Oct 13, 2014
  6. simona

    simona Active Member

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    You have to be very careful. The regular dialling we do is a product of two things, the pellet drop and the offset between the line of sight and barrel. An illustration of this is to take the example of two rigs which are identical except that one has a 2.5 inch offset and the other has a 3.5 inch offset.

    On the flat the number of clicks between say 42 and 50 yards will vary between these rigs, though the pure drop of the pellet between these distances will be identical. The clicks are different as the rigs have different line-of-sight to barrel offsets.

    If you shot both of these rigs at a target 50 yards away, but inclined such that the distance perpendicular to gravity was 42 yards, the click compensation for height (the number of clicks subtracted from the 50 yard value) will be identical on each rig as only pellet drop is affected by target angle not line-of-sight to barrel offset. Clicks equal to the pellet drop difference between 42 yards and 50 yards at 50 yards will have to be subtracted. This is not the same as dialling for 42 yards as only one of the two factors we dial for is changing.

    The component of dialling concerned with reconciling the line-of-sight to barrel offset (the bit that varies between the rigs) is only affected by distance from muzzle to target - the elevation of the target will not affect this. The other component of dialling, related to pellet drop, is identical between the rigs so the compensation will also be identical.

    Be especially careful on steep close targets; for example it s no good dialling for 10 yards on a mega high 13 yard target as most of this dialling difference is just to close the line-of-sight to barrel offset, what you need to do is subtract an elevation value equal to the tiny difference in actual pellet drop between 10 and 13 yards. In reality this is so tiny as to be meaningless!
     
  7. dave croucher

    dave croucher FT, the sport where simple becomes complicated

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    Well Simon cleared that up:):)
     
  8. DEAN C.

    DEAN C. Steyr Convert

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    Sometimes I wished that I had kept quiet!:rolleyes::eek::eek: I am going for a lie down after Simons answer.:D
     
  9. Brian.Samson

    Brian.Samson Allowed in Sales Staff Member

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    Chairgun can give you some of the answers, but it's a bit painful to do all the individual calculations, so I've tasked the ballistics engine of the windage game to generate a table for you to illustrate what Simon means.

    So to go with the example Dean gave of a 45 yard target at an angle of 45 degrees you would need to aim 51mm lower than you normally would.

    Its very common for people to drastically overestimate the angle. I haven't bothered to include the numbers below 15 yards or 15 degree's because the difference is negligible.

    With regards to the Riflemans rule - it's a reasonable approximation beyond about 30 yards, but below that you should ignore it, because it's wrong - sometimes by a huge margin!.


    (Download as a PDF)

    [​IMG]
     
  10. DEAN C.

    DEAN C. Steyr Convert

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    I bet everyone is printing that chart off as we speak!!!Thanks Brian.:cool::lev:lev:lev:lev
     
  11. TOOL

    TOOL Independent FT Pumper

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    Simon ,

    What would be the preferred angle of recline when perusing a copy of " Mediterranean Lothario's " ?


    Over and Sprout
     
  12. Brian.Samson

    Brian.Samson Allowed in Sales Staff Member

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    Depends on the muzzle velocity
     
  13. LittleJack

    LittleJack Active Member

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    So basically aim low unless under 15 yards
     
  14. Brian.Samson

    Brian.Samson Allowed in Sales Staff Member

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    Although that's for FT - the difference between a 2.25" scope height and a 1.75" scope height (a more likely HFT value) is so small that the two charts are practically identical. We're talking a difference of 1mm on the extreme ends of the chart.
     
  15. Brian.Samson

    Brian.Samson Allowed in Sales Staff Member

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    yup - rule of 15's ;)
     
  16. Brian.Samson

    Brian.Samson Allowed in Sales Staff Member

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    Just to test out what Simon said - I ran the program for a 2.5" scope height and a 3.5" scope height and the chart is the same give or take a fraction of a mm here and there. Then I ran it again for a scope height of 6 inches!.. again, this makes no difference to the answers.

    So, unless I've got my sums wrong - scope height makes no difference for inclined shots.
     
  17. holly

    holly Well-Known Member

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    IF

    If you get a very , very high sitter . then lie on your back with your head on the bean bag , cross your left leg over your right leg and rest the rifle on it . only snag is that your lower body will be across the shooting line to get your barrel in front of it . but that is not against the rules as they are . which just say your barrel should be in front of the line and your trigger behind it .??? HOLLY:)
     
  18. Brian.Samson

    Brian.Samson Allowed in Sales Staff Member

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    That's against the rules though Holly

    Rule 10 IV b - "... the back must not rest against any support that is not part of the shooter s seat."

    You can't rest your back on the ground with your head on the beanbag. Although I should imagine that for a seriously inclined shot that rule would probably be relaxed for that lane by the CM.
     
  19. BDL

    BDL Dangerous

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    Come visit Blaenau Gwent you'll soon get the idea :)

    Bri
     
  20. Yorkshiretea

    Yorkshiretea B Grade Bandit

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    This ^^^ is factual
     

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