How to adjust scope with a canted base?

This is a discussion on How to adjust scope with a canted base? within the Optics forums, part of the Sniping Related category; Thinking of getting the Bushnell 5-15x40 with a 20 MOA canted base, since as I understand it, I need about 45 MOA to get out ...

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  1. #1
    Junior Member jplehmann's Avatar
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    How to adjust scope with a canted base?

    Thinking of getting the Bushnell 5-15x40 with a 20 MOA canted base, since as I understand it, I need about 45 MOA to get out to 1000 yards and sometimes the "actual" available MOA could be only around 40, which is not enough.

    I understand that if I use a base of 20 and then have 40 usable MOA, I can get out to 60 "up" elevation maximum. My question is, if my least elevation setting were +20 (from the base), how would I manage to hit 100 or 200 yard shots (through the crosshairs), since this only requires a couple of MOA? It would seem to me like with the base I couldn't do this. A related question, is it customary to zero the scope at 0 MOA on the elevation setting, so that all the adjustment is in the "up" direction?

    Maybe to restate the same question but in a different way, I see how the 20 base helps me maximize my long range shots, but it doesn't increase my range (which would be 20-60 MOA). Therefore, I couldn't adjust to anything closer than +20MOA, and hence I still couldn't hit 1000 yards and 100 yards simply by adjusting the elevation. Maybe there's a way that zeroing at 300 yards or so fixes this problem, but I don't see it.

    I'm happy for links to articles that would explain this, I've done some reading but not seen it spelled out.

    thanks,
    John

  2. #2
    Senior Member ddd oo7's Avatar
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    Re: How to adjust scope with a canted base?

    a 20 moa base simply mounts your scope at an angle to the barrel. If your scope has 55 or more moa of vertical adjustment, then you should be fine. Just mount the scope on the 20 moa base and bore sight it. you should be able to zero at 100 yards, and then you will have an extra 20 moa of adjustment in the up direction. The canted base simply "borrows" the unused moa in the down direction of the scope. If the scope has 60 moa of adjustment, then it has 30 up and 30 down from center. with a 20 moa base it would have about 50 up and 10 down. clear as mud, huh.
    Rem 700 sps-v .308 in AICS
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  3. #3
    Junior Member jplehmann's Avatar
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    Re: How to adjust scope with a canted base?

    ddd oo7, thank you for your reply.

    In my example, I do not have 60 adjustable MOA, only 40. So am I correct in understanding that this scope will not be able to adjust to shoot at both 100 yards and 1000 yards (if the difference is 45 MOA), regardless of my base?

    While I want to shoot out to 1000 yards, since I am hunting also I need to be able to shoot at 100 yards, so it sounds like the 20 base isn't going to do me any benefits, though I'm not convinced I fully understand this.

  4. #4
    Senior Member ddd oo7's Avatar
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    Re: How to adjust scope with a canted base?

    It does not look like it will work then. a 15 moa base should get you a 100 yard zero and out to about 800 yards. I understand the idea of having one gun for hunting and precision shooting, and that was my original plan, but I have decided it is not practical. My precision gun is way too heavy to be lugging through the woods, so I still use my rem 700 270 with a sporter barrel and 3-9x32 for hunting. It will do great out to 300 yards-- which is about all I ever see anyway. That way I can set up my 308 for long range work and not worry about being able to hunt with it.
    Rem 700 sps-v .308 in AICS
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  5. #5
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    Re: How to adjust scope with a canted base?

    It will depend on where your 100 yard zero is within the reticule and the only way to find out is to mount it and zero it. Then count the down and up elevation to see what base you need.

    If you are shooting a .308 you will need approx 38 MOA of elevation. If the Bushnell Elite Tactical only has 40 MOA of adjustment in it (thats horrible BTW) then unless you are able to zero the scope at 100 at the very bottom of the reticule elevation adjustment... you ain't getting there. Chances are with a flat base and a 100 yard zero; you will be left with around 10 MOA of down elevation adjustment and 30 MOA of up elevation

    Using the 20 MOA base would not allow you to zero for 100. You would need a 10 MOA base based on this example.

    Again, I just can't BELIEVE there is only 40 MOA built into that scope!

  6. #6
    Junior Member jplehmann's Avatar
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    Re: How to adjust scope with a canted base?

    I'm shooting a Rem 700 .308.

    Mel said that the Bushnell 3200 claims 50 MOA, but he and others have cited that it's actually less than that [1]. But upon re-reading I can see that he recommends a 15 base instead of 20, so that he can still hit 100 yards. I guess I should just go with that and cross my fingers.

    [1] viewtopic.php?f=5&t=33678&p=331511&hilit=bushnell+ 15x40#p331511

  7. #7
    Junior Member jplehmann's Avatar
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    Re: How to adjust scope with a canted base?

    Yes, I understand that the current Tactical model is not the same, hence my post last week asking about the differences [1]. In fact you're (avolcek) the only one who replied to it.

    I guess I'll go with the 15 base and cross my fingers that I can still zero it at 100 yards, and it'll just go as far as it will...

    [1] viewtopic.php?f=5&t=40361

  8. #8
    Junior Member jplehmann's Avatar
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    Re: How to adjust scope with a canted base?

    Couple follow-on questions to mounting this Bushnell ET5154 [4] on my Rem 700 (could not locate answers online)
    1. With Burris XTR rings [1], can I use the Low rings or do I need Medium?
    2. I noticed with the base comes in short action [2] or long action[3]. How do I know which one to use? Mine is the Rem 700 SPS Varmint (EGW 1-Piece Picatinny-Style 20 MOA Elevated Base for Remington 700)
    3. Should I care about 1 piece vs 2 piece base?

    [1] http://www.snipercentral.com/shop/produ ... ucts_id=77
    [2] http://www.midwayusa.com/product/147376 ... tion-matte
    [3] http://www.midwayusa.com/product/985578 ... tion-matte
    [4] http://bushnell.com/products/scopes/rif ... al/ET5154/

  9. #9
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    Re: How to adjust scope with a canted base?

    Fast quick-hit answers!

    1. Low should be fine with a scope base and a 40mm OL.
    2. .308 is a Short Action rifle so S/A base
    3. Yes you should, get a one piece base and there will be less or no alignment issues.

    Edit... dangit Adam... you beat me

  10. #10
    Junior Member jplehmann's Avatar
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    Re: How to adjust scope with a canted base?

    Hey, I like multiple answers -- gives me more confidence!

    What do you guys think of scope ring offset inserts [1] instead of a canted base? Seems like this would be a more flexible solution and has the auxiliary benefit of "protecting the scope" whatever that means.

    [1] http://www.snipercentral.com/burrismounts.htm

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