Scope Problem Need Advice

Discussion in 'Long Range Hunting & Shooting' started by AWOLF, Jan 22, 2008.

  1. AWOLF

    AWOLF Member

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    Jan 21, 2008
    I just put a mark 4 with high ring mounts on the 243. The bottom of the scope is about1/2- 3/4" from the barrel. I had a weaver with low ring mounts and a ton of kills. I mount the mark 4 and zero for one hundred yards. I'm out calling this evening and here comes wiley. He stops at 150 yds and the bullet goes right over his head. I had that weaver so dialed in I new exactly where it would hit. I'm afraid I have to make a trip to the range and see where this pig on a stick will hit at 150 , 200 , 300 . I use to hardly ever miss. Lately it seems that's all I do. I shot better with the cheap glass.The weaver v16 was great for the $. What can you tell me about the ring height ?
    I'm trying to post a pic so you can see. This gun has a great history til the scope change. I going to the range this weekend to try to understand what the heck is going on.These two misses with the old setup would have been "Wham Bam TYM!! I can assure I'm not suffering coyote fever at this point in my life. I wish that were the case. I get a little excited but not to where I pee my pants. I was out with a buddy this last weekend. He nearly defacated on himself.Can you tell me what rings I should get. The current rings are heavy duty with four screws on each ring and made of steel. I measured about 1/2" gap (barrel and scope gap at closest point) and had to shim the rear mount I belive about 5 layers of premium coors light shimming aluminum to get it on paper. Thanks
    [​IMG]
     

  2. diderr

    diderr Well-Known Member

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    Dec 16, 2007
    Get yourself a badger 1 piece rail picatinny, and medium height rings (preferably mark 4 rings) Thats my setup with my mark4 and it works perfectly with the 50mm objective lenses. You got good glass, you should get good mounting hardware too.
    diderr,
     

  3. James Jones

    James Jones Well-Known Member

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    I would bet that it has more to do with poor shooting position and scope site picture than anything , that scope is pretty hiogh and the chances of you getting a good cheek weld are slim unless you got a very long face.
    Try taping a few pieces of foam to the comb of youe stock to get your head back into positiopn and go shoot some groups.
     
  4. chain

    chain Well-Known Member

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    What James Jones said... I have done it before.. missed too.
     
  5. mikenc

    mikenc Well-Known Member

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    Jul 23, 2007
    That scope appears way too high from my opinion. I found with the Leupold 30mm tubes the ring height can be reduced quite a bit. Try a lower set of rings and perhaps an "anti-cant" device or level. With the scope that high, any "cant" in the rifle is sure to make a big difference.


    Mike Alford.
     
  6. long ranger

    long ranger Well-Known Member

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    Sep 13, 2002

    By raising your scope up off the bore , you have altered your line of sight from your trajectory intersection. You will find that at 200 yards your trajectory is still rising above your line of sight.
    The true trajectory , obviously has not changed, just the position that your eye now sees its intersection. It is a bit confusing to explain, but once you hit the range it will become quite apparent what I mean. Basically you have changed the geometry of your rifle and it will take some getting used to it before you are able to have the rifle perform as it did before.
    Your drop chart will need to be altered to accomodate your new come up values as well.

    I am not sure why so many "experts" insist that the scope be mounted as close to the bore as possible, this makes no sesnse to me unless you have a very short neck.
    More importantly your scope should be at a height where the objective is where your eyes center is when you have a good comfortable and repeatable, cheek weld. This can mean having to increase or decrease the ring height AS WELL as the stock cheek rest height.
    The secret to accuracy is removing as many variables as possible, so to have your eye and cheek in the same place everytime is of benefit, moving your face to find the optic center of your scope is not conducive to accuracy.
    For someone to advise you your rings are too low or too high without seeing where your eye is in relation to your objective lense, and whether you have a good cheekweld, is ridiculous.
     
  7. davewilson

    davewilson Well-Known Member

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    that scope would have to be a heck of a lot higher than it is now to miss at 150 yards if the relationship of Line Of Site and centerline of bore were the problem.
     
  8. Augustus

    Augustus Well-Known Member

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    I hate to be the bearer of bad news but I just played with the ballistic program a little and it appears that a 308 loaded to send a 175 SMK at 2720 fps and zeroed at 100 yds with the scope 1 in above the bore would be about 1.5 in low at 150 yd. If the scope were 4 in. above the bore the round would hit dead on at 150 yd. Also you could change your sight picture from top to bottom of the scope and not create the error you are talking about. You better shoot her again and see where she goes. When you start talking about shimming scope rings it almost gives me the hives.
     
  9. long ranger

    long ranger Well-Known Member

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    Try running your program again using 2.25" center of bore to center of objective.
    The scope is 1/2 between top of barrel and bottom of bell, add another 1/2" for center of bore to outside of barrel and divide 50mm by 2 which will give you just over 1.0" added up will be very close and likely just over 2.25" center of bore to center of objective lens, as the barrel is certainly closer to 1.2" on diameter.
    This will alter your equation a fair bit.
     
  10. Augustus

    Augustus Well-Known Member

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    This was just an example of how little big differences in scope ht. will effect poi at 150 yd. when zeroed at 100 yds. No need to get really technical here, in the example there was 3 in. difference in scope ht. causing a 1.5 in deviation in poi. Obviously not enough to shoot over a deers' head. The more likely culprit is the scope shifting around in those shimmed up rings.
     
  11. long ranger

    long ranger Well-Known Member

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    I agree there are likely several issues at work here.
    Many guys do not take into account just how much difference there really is in mounting a scope up higher due to the bigger objective lens on many of todays scopes.
    I also am NOT a fan of shims, preferring to use good rings and rails for mounting big optics.
     
  12. Augustus

    Augustus Well-Known Member

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    One thing I ran into once was a scope sliding back and forth under recoil in the rings mounted on a sloped base, this can cause a lot of vertical deviation. The effect of shimming underneath the scope on the rear would cause the same problems if the scope were to shift foward or backward.