Anyone ever dope their variable mag scope at less than full magnification?

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  • SmileDocHill

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    I have a Vortex Strike Eagle 1-8 with BDC reticle.

    Short version: The lowest/last hash mark is designed to be 600 yards. While it isn't the reason I got this scope, I would like to use it for one of the shoots at Atterbury where they shoot at 300, 600, 800 yards. At 800 yards my holdover will put POI nowhere near a point of reference on the reticle. My logic is to move the magnification down to say 5 or 6 and get the dope for 600, 700, 800 at that magnification. This should pt the POI within the site picture so there are some reference points nearby. I know it isn't ideal by a long shot, and the spacing of the hash marks won't at all be reliable as drop indicators since they were designed for 8x. I'm simply using the lower magnification to allow the POI to be near some reference point.

    Has anyone ever done this?

    I'm taking a road trip to the CMP Talladega Marksmanship Park this weekend and will have all day Saturday (possibly some time Sunday) to shoot out to 600 yards. They have digital targets so I'll not even have to take time to change targets, work the pits, call the range cold, change shooting lanes for different distances... It is a lot of shooting time so I'm trying to get my itinerary and shooting goals squared away ahead of time.
    #1 goal is to get the AR with the new scope squared away, dialed in, and dope confirmed for the main 3 .223/5.56 ammo's I use. Then I'll play with changing the magnification to a lower power and see where that puts the POI's for 100, 200, 300, 600 yards then I should be able to use this information and ballistic calculators to get a close estimate and be "on paper" at 800.

    Regarding the road trip aspect: I looked at closer ranges but Young's is too expensive for what will only be used 1 or 2 times a year at best. Bass and Bucks range yardage is great but shooting positions are not at even yardage. Plus, I'm just looking forward to getting out of town. I rarely go anywhere. I'm open to someone coming along with me, should be a fun time. I'm leaving Friday around 2-3pm cheap motel or possibly even camping Friday night somewhere nearby TMP, and I'm undecided on leaving Sat. night or staying to shoot or see something Sunday.

    Any thoughts on any of this?
     

    Goodcat

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    If you take a SFP BDC scope, as you know, one specific (usually too end) magnification will result in accurate sub tensions. Each line represents the holdover necessary for average 223 bullets in your case. If you go to a different magnification, they will obviously be off.

    However, your theory is correct. If you take the time to find where the bullets impact at, say, 5 magnification, you could dope those impacts too. Kind of like making your own BDC.

    However, when you are shooting 200 yards plus, 8 power is not a lot of magnification and while not necessary, still provides a very wide FOV. I’ve got a strike eagle 1-6 if you want to work out a trade plus $50 from me!

    edit: Oh and don’t expect those lines to workout to even distances at a different zoom. So if 8x is 200, 300, 400, 500 for instance. Half power might be something like 200, 387, 593, 798
     
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    SmileDocHill

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    We shoot at Bass & Buck's and we have never had a problem setting targets and whatever distance we need the to be.
    That is interesting to know. I have zero first hand experience. I was basing my information on the website saying benches at 350, 550, 750. I'll have to reconsider my options. I mean, the drive is 4 hours closer!
     

    SmileDocHill

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    I wonder if returning exactly to the same lower magnification level is repeatable for long range precision?

    This is what I think I'll find as the main problem. 1) getting the adjustment ring to the exact same position each time. 2) are the internals accurate enough that it is actually the same even if I line them up perfectly based on exterior marks.
    I'm not really ever guilty of being a "safe queen" gun owner and more on the end of the spectrum where I treat guns like tools and if it makes it more functional have no problem modifying things. To that end, I've considered making a very subtle hair line scratch on the magnification indicator to more accurately reproduce the adjustment position. Otherwise I'm lining up a white dot to the bottom of a number and that is not nearly as precise.
    Internal reproducability: I'll always get to the point I establish by rotating from the same direction. That should prevent any play in the screw threads from entering into it but that is about all I can control from the outside.
     

    natdscott

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    Why the hell wouldn't you just move the dials on the scope?

    They do that for a reason... ;)
     

    natdscott

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    Oh, and you don't need ballistic calculators to get on paper at 800.

    Just come up 10 minutes from 600. Maybe 12. If it's not at least a 20" tube, and at least 77's, then I wouldn't expect the 10 MOA to quite work.

    But keep in mind my advice is coming from the days of the Springfield and the M14, and it's still pert near dern true.

    The targets are big.
     

    SmileDocHill

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    Why the hell wouldn't you just move the dials on the scope?

    They do that for a reason... ;)

    Painfully obvious solution! I have no counterpoint to that suggestion, only an explanation to my logic which is based on almost zero experience and only mentioned for the sake of discussion.
    I have a much better riffle for NRA/CMP type competitions if I want to see how well I can do.

    The rifle I have this scope on is a little experiment of mine where I'm trying to find the most broad spectrum utility setup for the rifle that require the least adjustments as possible. A magnification adjustment is much quicker and less likely for me to forget it needs changed back than dialing in elevation changes. Over this summer I'll be using it at events like CQB/ carbine clinics, Atterbury rifle pop up (quick acquisition out to mid range distances), CMP/NRA/Revere's Riders type KD events from 100-600 yards and general range trips. It will for sure be a master of none but the fun is seeing how well I can do at a broad range of things with one setup vs really well at one thing.
    This year is getting really good with 1 rifle and having fun with a wide range of event types, next year is focus on getting a different rifle for more specialized uses based on the event type I want to focus on.
     

    Clay Pigeon

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    That is interesting to know. I have zero first hand experience. I was basing my information on the website saying benches at 350, 550, 750. I'll have to reconsider my options. I mean, the drive is 4 hours closer!
    Rifle benches all sit at the firing line, berms at 350,550 and 750 depending on who's range finder you believe.
    Here's a pic of the longer ranges firing line.

    View attachment 77375
    The rifle range now has a roof...
    Ignore the bottom pic, It's Elwood CC
     

    Rookie

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    That is interesting to know. I have zero first hand experience. I was basing my information on the website saying benches at 350, 550, 750. I'll have to reconsider my options. I mean, the drive is 4 hours closer!

    I usually bring my own target stand and set it up wherever on the 750 yard range
     

    SSE

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    You are correct in the idea.
    Just do not over think it, find out what power equals what range and you are good to go.
    I have done this on several. Works good.
     

    Ggreen

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    Id mark the exact spot you dope with a color coordinated line across the zoom to the body of the scope. Or just get a ffp mil mil lpvo
     

    Clay Pigeon

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    Yes, I am. However, I only do it when no one is using the 750 range (which is more often than not)
    LOL,,
    I'm with the group that usually brings the child size 4wheeler (and a blue chevy and a blue ranger 4x4's) to change targets. Not the old men that have 20 steel and paper targets up most weekends. We are usually shooting a few Savage Lapuas and I shoot a few PSS's or 40X's. If you see us say hello.
     

    SmileDocHill

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    Yes, I am. However, I only do it when no one is using the 750 range (which is more often than not)

    LOL,,
    I'm with the group that usually brings the child size 4wheeler (and a blue chevy and a blue ranger 4x4's) to change targets. Not the old men that have 20 steel and paper targets up most weekends. We are usually shooting a few Savage Lapuas and I shoot a few PSS's or 40X's. If you see us say hello.

    You guys have me totally rethinking my options now.
    TMP pro's: instant feedback with digital targets, never having to stop and call cold range to check where my poi is and coordinate with everyone else that's shooting, beautiful facility, with a store full of Garands, 50+ shooting positions and rumor is it is never packed, needed getaway/ road trip aspect. Con's: 8 freakin hours away!
    B&B pro's: 1.5 hours away vs 8, camping options somewhat nearby, could shoot 2 days with the drive time I save, won't be as hot as Alabama, range is farther than 600 yards.
    Con's: feedback much slower and will need targets, I anticipate it taking at least 2x the time to get the same things accomplished.
    I'm getting too old to make decisions.
     

    Hop

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    Hmm... 44 MOA per revolution. A 1/4 turn up on the turret would get your 12 MOA 800 yard zero while still using the max 8x magnification.
     

    Dean C.

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    Personally I would dope the scope at the full 8 power for repeatability sake personally. But this problem is part of the reason I dumped a bunch of money on my Trijicon 1-8 to get the FFP and much nicer glass.
     

    SmileDocHill

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    Hmm... 44 MOA per revolution. A 1/4 turn up on the turret would get your 12 MOA 800 yard zero while still using the max 8x magnification.

    Yes, yes, I know, natdscott made me realize I was doing my typical issue of waay over thinking the problem. This is how most of my threads go. :-)
     
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