Scope height over bore (question for long range shooter)

Discussion in 'Competition Shooting' started by Nathantc, May 16, 2013.

  1. Nathantc

    Nathantc New Member

    560
    0
    0
    ok i been playing with my ballistics computer and it seems that for my .270win its better to have my scope at about 3" than to have it at 1.75" if my only range that i use it for is between 200-400 yards, no closer rarely farther.

    according to the computer it will require the lest about of hold over or elevation adjustment when zeroed right at 300 yards

    i have always been told the closer to the bore the better but this is disproving that completely
    the closer to the bore the bigger the drop from 300-400 yards,, noticeably

    higher = less rise at 200 and less drop at 400 with a 300 yard zero
    closer = more of both

    am i doing some thing wrong or is scope hight really making that big of a difference

    also you might note that all of the super long range sniper rifles have the scope pretty far from the bore due to rifle design but could that be a benefit for extreme distance (im not talking about the puny .308 either, im talking about 338 lapua, 408 cheytec, 416 barret, and of course the 50 bmg)
     
    Last edited: May 16, 2013
  2. Crazycastor

    Crazycastor New Member

    481
    0
    0
    How much does the bullet drop from 300 yards to 400 yards? I think my 30-06 drops 27 inches. Could that be a factor?
     

  3. Nathantc

    Nathantc New Member

    560
    0
    0
    not sure i would have to look again,, but if zeroed at 300 the drop is different with different scope heights over the bore
     
  4. Txhillbilly

    Txhillbilly Active Member

    4,435
    29
    38
    On my bolt action rifles,I try to set each one up the same as far as scope height from centerline of the bore. I always zero my rifles at 100 yards,but have set my 300 WM at 200 before,but I shoot at all types of ranges from 50 yards to 1200 yards.
    Depending on the style of stock,and size of the scope that will determine the minimum height that you can mount a scope from the bore.You mainly want to be able to have a good cheek weld on the stock,and still be able to look directly through the scope on every shot with the least amount of body movement. If you change it at all,your shots will not stay the same. It doesn't matter whether your 1" from the centerline or 4" from the centerline of the bore,if you are not in the same position every time,you'll be off on your shots.
    The ballistics for the bullet will remain the same,but by changing the scope height perimeters on a ballistics calculator,you changing the angle in which the round is seen from your view,and that changes the drop rate for the same distance. When the round is fired,the trajectory of the bullet doesn't change because you mount your scope higher or lower to the bore.

    Example- My Savage 12 FLVSS and my RRA 20" varminter have the same 6-24x50 Weaver Classic Extreme scopes on them. The scope on the Savage is lower to the bore than the scope on the AR15,the reason is the stock design. If both rifles fired the same bullet at the same velocity,the one shot out of the Savage would seem to drop more at the same distance because the scope is setting closer to the bore centerline. But in reality,the bullets are doing the same thing,just at different shot angles.
     
  5. c3shooter

    c3shooter Administrator Staff Member

    21,445
    555
    113
    There is more to it than simple height of scope- Those rifles with very tall scopes also have a straight line design. Otherwise you are getting a scope mount that will flex more, not having a stock weld to give a reproducable aim shot to shot, etc-

    Otherwise we would have 12 inch mounts on all rifles, and be shooting at 3 miles.
     
  6. bigjim

    bigjim New Member

    560
    0
    0
    Without information on the scope, I am not sure we can answer. I always thought it was measured from center bore of the barrel to the center of the scopes objective, so a 50 mm would be different than a 40 mm objective. The other factor is your cheek weld on the stock and being able to see down the scope correctly without having the rifle floating in the air unsupported.

    Jim
     
  7. Nathantc

    Nathantc New Member

    560
    0
    0
    not talking cheek weld at all,, im just saying i have noticed that it will change your drop values with different scope heights,,,

    regardless of the scope itself,,,
     
  8. Txhillbilly

    Txhillbilly Active Member

    4,435
    29
    38
    And it doesn't matter at all,if you don't have a good cheek weld on your rifle if the scope is mounted 3"-4"-6" or a foot off the bore centerline. You won't be able to hit $hit with the rifle.
    No matter how high or low the scope sits on a rifle,it doesn't change the ballistics of any bullet. It just changes the ballistic perimeter because the scope to bore centerline has changed.

    I don't know what you're trying to accomplish.If you are only planning on shooting out to 400 yards even most cheap scopes have enough adjustment range to shoot that far.
     
  9. Nathantc

    Nathantc New Member

    560
    0
    0
    i understand and know this

    but i was just playing with a ballistics computer and noticed that with certain scope heights it will make it seem to shoot flatter at different ranges,,, im not fool and i know that it doesn't change the bullet path, just the straight line of sight angle threw the bullets arch... just wondering if anyone has tried to use this to some advantage
     
  10. bigjim

    bigjim New Member

    560
    0
    0
    NO, just comfortably mount it so you can see what you are shooting at. And that the front objective is 1/4 to 1/2 inch off the barrel. And that the bolt does not hit the scope when you open the breach.

    Jim
     
    Last edited: May 27, 2013
  11. Flat Tire

    Flat Tire New Member

    1,905
    0
    0
    The bullet doesn't fly different. There is two basic things to think about, first the higher the scope is, the more you will find bullets that stray left and right. The higher it is the harder it is to hold perfectly over the barrel. When the scope is low on the barrel it will pick up more heat when you have to shoot many shots in a short time frame.
     
  12. John_Deer

    John_Deer New Member

    6,624
    1
    0
    C3 has already nailed it. You can put extra high mounts on any gun and the rifle will appear to shoot flatter. But you are giving up durability with the extra high mounts. Yes, you can sight the gun in at 300 yards. Yes, it will shoot flat. But every time you transport the gun in a vehicle you will have to sight in the scope again. Just shooting the gun will knock the scope off target.

    Use the lowest mount you can and still operate the bolt. The mount will be durable and dependable. You can shoot just as far but you will have to hold over the target.
     
  13. triggerjob

    triggerjob New Member

    258
    0
    0
    To visualisewhat is going on, draw an arc across a piece of paper, then lay a straight edge parralel to the arc across it.

    The arc represents the bullets path, the straight edge is the scope line of site. As you change the hieght of the straight edge the contact points along the arc change. Tilting the straight edge will also move the contact points.

    By changing scope hieght and angle on the bore you are altering how the line of site and bullet arch intesect. Where the line of site and bullet arch intersect equals 0 hold over, past that point adds hold over and before that point adds hold under.

    Not sure if that clears it up or foggs it more but that is what your ballistics program is showing you.
     
  14. triggerjob

    triggerjob New Member

    258
    0
    0
    It can be used to your advantage if you are shooting targets outsided of your scopes reticle click range. By raising the scope and tilting it forward, you increase the bullet arc extending the bullets range as well as where the LOS crosses down range.

    Its the same principle as the old flip up long ranging tang sites. Cept with a high powered rifle a little goes a long way, shimming the rear of a scope base by the thickness of a bussiness card can dramatically alter this relation ship.
     
  15. epleyjoseph

    epleyjoseph New Member

    62
    0
    0
    I think triggerjob is the only one who actually tried to answer the question instead of acting like Nathan was stupid for asking, answering different (unasked) questions, or generally discussing other things besides the ACTUAL question.

    Thank you, triggerjob!