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Thread: scope mount allignment

  1. #1

    Default scope mount allignment

    Ran into a lkittle problem the other day.
    When mounting a scope on a new (to me) rifle we (the more experienced & myself) noticed that the mount holes for the bases didn't seem to be directly over the bore. We fiddled arround a little bit, went ahead and lapped the ring went on our merry way to the range. There I observed exactly what I thought would happen. Less than an inch grouping at 100 yds. bu when I moved to 200 all my shots were exactly 3 inches to the right.
    My fear is an improperly drilled receiver. Thoughts?

    Rich

  2. #2

    Default

    Added note. This is a facotry winchester.

  3. #3

    Default

    it sounds like you hit the nail on the head, try a 300 yard shot and see. aditionally a scope out of plumb coud do that, but if it is visiblt off......bummer. souds like a re-tap.

  4. #4
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    Default Adjustment?

    Why not try six clicks to the left?

    If the scope mounts are off, and it sounds as though they are, (about average for a Winchester) but you have enough adjustment in the scope to center the shots, why not do it? I'm confused....again.

    If the scope is off at 200 yards it is off at 100 yards and 500 yards and.....
    The scope mounts can't make it on at one distance and off at another. Are you out of adjustment? (No more clicks)
    Is there nothing so sacred on this earth that you aren't willing to kill or die for?



  5. #5

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    I had hopes of setting this firearm up as a backup rifle for medium game (deer, goat, sheep etc.). I planned on using the 'MPBR" aiming convention. I would rather caculate and expect a consistent shot placement rather than +/- 3" of the MPBR but that might be little too much to ask as I am new to center fire use as well as hunting.
    I purchased "the only rifle I will ever need" (quote to the wife as she wrote the check for the Kimber Montana 325 WSM) a while back but I wanted a little smaller caliber rifle (7mm WSM) to play with at the range for long distance and as a backup. Bought the Super Shadow off of an on-line auction place for what I thought was cheap (go figure). Trying to bore site the little Monarch 3-9 showed the problem. I couldn't beleive that Winchester would ship a rifle (albeit cheap) with an improperly drilled receiver. I examined the bases that came with the rifle as I thought they might somehow compensate for this but I can't be sure (rifle new came with a scope mounted). They look straight. They are Weaver style. I was thinking that I might be able to 'customize' the bases to compensate.
    The rifle shot fairly well (under 1") at 100 yds and so I was excited that it would be OK. Now I don't know. Really hoping to just compensate in elevation for distance. It would be annoying the have to calculate both az & el.
    In the mean time I'll try to work up loads for a 200gr. tsx and the 220 gr. sierra for the 325.

  6. #6
    Member Kay9Cop's Avatar
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    Default

    In order for your scope to be off 3" right at 200 yards but dead on at 100 yards your scope would have to be mounted 3" off center of the bore, that's plain geometry. I'm with Murphy on this one, if you're off at 200 you are also off at 100 but by a lesser amount. If you have scope adjustment left then just move the cross hairs. If you don't have adjustment left in the scope then send the rifle back.

  7. #7

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    are you out of windage adjustment in the scope?

  8. #8

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    I do have adjustment left and did adjust to zero at 200. Checked it at 100 and shot consistently 3" to to the left.

  9. #9
    Member Kay9Cop's Avatar
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    Default

    The only other possibility is that the scope is seriously tilted within the mounts and as you move the vertical cross hair up and down to compensate for range you are actually moving the gun left to right because the vertical cross hair is not perpendicular to the bore.

  10. #10
    New member George's Avatar
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    Default confused also

    The simplest solution is to make sure the gun and ammo are accurate and the scope vertical is vertical to the bore/action. Then sight in for about 2.5" high at 100 and call it good. K9 may have the best logical answer to the odd bullet impact at 300. The only way a bullet can have a consistently curved trajectory where it's windage is on at 100 then not at other ranges is the very small rotational or "spin drift" effect, AKA Magnus effect. That drift would be to the right for right twist barrels. But that drift is very small- usually something less than 1/2" at 1000 yds.

  11. #11

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    I originally set it to shoot 2.5" high at 100. Then at 200 all shots were just off the 6" sticky dots (to the right). When originally sighting it in I did notice that the move from 25 yds. to 100 took more lateral adj. then I thought would be necessary.
    I will take another hard look at the setup in the light and see just what is not plumb. Thanks for the help. I will report back with my findings.

  12. #12
    New member George's Avatar
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    Default good

    Hope you do report back after the re-set. We all learn by these. And, it's always hard to diagnose things like this... but I think K9 may be close. The scope doesn't have to be exactly centered over the bore axis nor does the "Zero" setting on the scope windage be in perfect alignment with the bore axis. Actually both mis-alignment conditions are more the rule than exception with most guns and scope mounting. As long as you have enough adjustment remaining in the scope and the vertical in the scope is at least parallel to the vertical in the gun and the gun is not canted when shooting- the windage variation should be fairly consistent at all practical ranges. Example- if center of group is 1" left of target at 100 yds. it should be about 2" left of target at 200 yds. and about 3" left at 300 yds. and so on. External conditions like wind of course will skew the results and canting during shooting will really foul things up.

  13. #13
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    Default

    It is a possibility that something is not up to snuff concerning the parallex.
    Some scopes are adjustable for this and it should not have a lot of impact even if it is not set correctly but this is about the only thing I can think of that could cause the problem you are presenting.
    I would also recommend you have a friend shoot the rifle and see what happens to rule out human error.
    Are you permitting the barrel to cool down in between groups?
    Tennessee

  14. #14

    Default

    The scope was used?
    Maybe the tube is bent?

    Lots of maybes here, but if you have a Leupold send it in to be fixed or replaced. You can check your scope on a set of V-blocks or try cutting 2 Vs on either end of a cardboard box. Rotate the scope and you should be able to tell if it is bent.

    What kind of mount are you using? Those Leupold STD mounts with the windage screw are notoriously poor for remaining in alignment.

    Also, was the scope "returned to zero"? If you have click turret adjustments, you can move the reticle all the way to one side, then count the clicks as you move it to the other side, then move it back half as many clicks and you are zeroed (roughly) in the middle of the scope's movements. Do this for vertical too.

    If your scope mounting holes are out of true, likely this can be fixed by having a PRECISION Gunsmith establish alignment by enlarging to an 8x40 hole.

    Are you using a single piece base?
    Pretty hard for these to be that out of whack. My bet is something else. Hope your scope has a warranty that transfers.

    Try another set of mounts and rings, and have a gunsmith check your mount job and scope movement on a grid collimator. If you are a serious shooter, buy one yourself. The scope should track evenly every time. Try moving 10 clicks L, 10 clicks up, 10 Clicks R, then 10 clicks down. Should be back where you started on the grid.

    Unless you bought Leupold or Burris, a used scope can be a pile of trouble. Pretty easy for someone to overtorque the turret movement if they are ham fisted.

    Good luck! Don't blame Winchester just yet!

  15. #15

    Default found the problem?

    I think I finally figured out the problem I ran into here.
    I sold the 7mm WSM but kept the scope and put it on a Whelen I recently acquired. When sighting it in the point of impact would not change after turning the windage knob. Wouldn't matter how much I turned it. Finally got out a screw driver tightend the screw in the center of the knob. THis did the trick. Dialed in the scope and it seemed to work fine.
    Not sure if this was the exact problem but the scope seems to work on the Whelen pretty good.

    Just an update.

  16. #16
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    Default Took ya long enough...

    eh? I knew that from the git go... :P

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