Mounting my scope: is this usual?

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  • davsco

    Ultimate Member
    Oct 21, 2010
    8,607
    Loudoun, VA
    especially if you don't need any cant/slope for your scope (ie if you will be be shooting maybe 5-600 yds), you can just get a set of rings. some bases have some elevation built in (ie 10, 20, 30 moa, etc) so that you don't bottom your scope out when dialing/shooting out at longer ranges such as 1000+ yards.
     

    ras_oscar

    Ultimate Member
    Apr 23, 2014
    1,666
    This evening I reset the scope. Counted the full adjustment range and set it in the middle on both axes. Then I removed the scope and shimmed the rear ring with a piece of stranded electrical wire. Loosened the mount base clamp and adjusted the windage to zero in on the laser dot. Now I have a scope at center adjustment and that zeros on the laser: at 30 feet: that's as far as I can go without making some noise. I'm ready for the range now. Ill decide late whether to keep the mount or swap it out for something better.

    Just to satisfy my curiosity: is there a one piece mount with build in windage and elevation adjustment for rough sighting?
     

    davsco

    Ultimate Member
    Oct 21, 2010
    8,607
    Loudoun, VA
    if you are shimming with wires, thinking you've already lost the battle. something is wrong with your mount, scope or the way you've attached everything. i'd take it in to a gunstore, cabelas, etc and just see if they see anything obvious. 308 isn't a magnum but does have decent recoil, and wire strands are going to move around or compress on you and shift your scope.

    not aware of a mount with elev or windage adjustments. have seen some bolt rifle bases that have windage adjustments. i've mounted a couple dozen scopes on AR's and bolt guns and never had more than a MOA or two or three adjustment either way.
     

    ras_oscar

    Ultimate Member
    Apr 23, 2014
    1,666
    your punishment for answering my silly questions is another silly question:

    When I place my eye to the scope, the crosshairs appear to move relative to the target when I shift my head. How do I minimize this effect? FYI the scope has a 4" eye relief and that is approximately where my eye sits relative to the eyepiece of the scope.
     

    outrider58

    Eats Bacon Raw
    MDS Supporter
    Jul 29, 2014
    49,818
    your punishment for answering my silly questions is another silly question:

    When I place my eye to the scope, the crosshairs appear to move relative to the target when I shift my head. How do I minimize this effect? FYI the scope has a 4" eye relief and that is approximately where my eye sits relative to the eyepiece of the scope.

    Don't shift your head.
    From right to left? Does the sight picture fill the entire lens. No black edge visible? Cheek firmly placed on stock?
     

    Qbeam

    Ultimate Member
    Apr 16, 2008
    6,074
    Georgia
    Are you getting dark/black areas moving when the crosshairs are moving? As you move your head, your eye alignment also moves. If you are not looking directly through the scope, and at the proper eye relief range, you will have the crosshairs moving along with the scope tube (black areas) moving in the picture.

    Q
     

    Major03

    Ultimate Member
    That shifting effect of the crosshair relative to the target is called parralax. Your human Mk1 eyeball can only focus on one object at a time. If the image of the crosshair isn't on the same focal plain as the image of the target, it can appear to float as your eyeball moves. If you're really good at holding position and don't move your eyeball relative to the scope and rifle...you won't even notice it. But, if you move your eyeball at all from shot to shot...it introduces error and will open up your shot pattern. Everyone moves around a little.

    I'll use an example to explain. Pick a spot on the wall as your target for this example....hold a thumb out and extended from your body, close your non dominant eye and "sight" on your target as if your thumb were a front site post. Now move your head around while holding the thumb still...it'll look like it's moving all over the place relative to the target. Now imagine having a friend hold their thumb out...only inches away from the target on the far wall. Now move your head around...it'll stay exactly the same relative to the target. That's because it's on the same focal plane as the target. That's what's basically happening with your scope.

    Most scopes will have parralax adjustments to move the reticle onto the same focal plane. The higher end "tactical" scopes usually have it as a side knob, and older scopes or target scopes often have it on the objective bell. Most people think it's for focusing the scope...but it's for removing parralax. Use the yardage indicators as a "getting me close" indicator, and make adjustments from there. Some scopes have a set parralax and you can't adjust for it. My M40A1 USMC sniper repro with a fixed 10X Unertl is like that. Parralax is set for 300 yds. No problem if I'm shooting that far or further...but I need to be careful about my cheek weld / alignment if I'm trying to get tight groups at 100.

    Parralax is less forgiving at higher magnifications and at closer ranges. Often my best groups are shot with less magnification for this reason. If you find you're adding magnification and your groups start to open...it's parralax.
     

    danb

    dont be a dumbass
    Feb 24, 2013
    22,704
    google is your friend, I am not.
    what they said. Its like the old joke "Doc, it hurts when I do this" so the doctor says "So dont do that!"

    To minimize the movement of crosshairs, don't shift your head. Make sure you have a comfortable cheek weld where you think you will be consistent then adjust to scope to get the right sight picture (no shadow, no bubble, no black, etc.)

    For the record, when I shoot straight ahead, from a bench I am dead on. When I shoot a target higher/lower or to the left/right sometimes my Point of Aim shifts. Not a large amount at 100 yards, but my rifle is accurate enough I notice it. That is, I hit slightly right/left/up/down relative to the crosshairs. Because my eye is not staying in the same place relative to the scope. Something I am working on, but yeah getting the same weld in different positions can be hard.
     

    Major03

    Ultimate Member
    Use the parallax adjustment in the scope to minimize the effect if you have it. Most people will just put their parrralax adjustment (most people think it’s a focus) on the distance to the target and start shooting.

    This is a mistake. You want to fine tune it, check by moving your head and watching for the reticle moving or staying stable. Make minor adjustments until it does stay put. Depending on the scope, the target may not be in focus anymore. Parralax reduction takes precedence. If your target is a touch out of focus no big deal. If it’s a lot out of focus you have a faulty scope and should have it replaced or serviced.

    Taking the time to do this will make small mistakes in your shooting position and eye alignment less problematic and your groups will thank you for it
     
    Last edited:

    onedash

    Ultimate Member
    Feb 24, 2016
    1,026
    Calvert County
    Leupold makes a mount that you can center side to side but not elevation. I have one on my7400. With a good rail and rings or a good unimount you shouldn't need it unless the rifle is messed up. Then it probably doesn't matter what you strap to the top of it. Badger Ordnance has excellent discounts for military L/E. I put one of their unimounts on my AR-10.
    http://www.badgerordnance.com/unimounts.html?___SID=U
     

    ras_oscar

    Ultimate Member
    Apr 23, 2014
    1,666
    Range report:

    Had what I consider my first productive day at the range yesterday. Yes. the wire under the rear mount fell out, as I was told on the forum would happen. I didn't listen, feel free to abuse me briefly. (Need to Loctite the scope screws and toss a couple allen keys into the range bag for future repairs). Borrowed a hex key and tightened the scope up. Ran a box the do major adjustments at 50 yards, then focused on 100 yards. most rounds were grouping in a 6 inch circle clustered around the aim point. At this point I'm going to leave the scope adjustments alone and concentrate on closing in the groups using parallax adjustment and technique. Then I'll make a final call on final adjustments and move to holdover at 200 yards.
     

    Major03

    Ultimate Member
    Based on the pic earlier in the thread, it’s a single base scope and has two separate rings, right?

    Lapping could help, but I really doubt it’s what is causing the misalignment by that much.

    Again, I go back to truing the barrel extension to the upper. My bet is that would center everything up and your rifle would also be a bit more accurate.

    Simple job for a gunsmith, not too hard a DIY job with the tool from Brownells and some guidance.
     
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