effects of elevations on custom turrets

Discussion in 'Long Range Scopes and Other Optics' started by JohnRP, Jan 24, 2014.

  1. JohnRP

    JohnRP Active Member

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    I'll be going on a sheep hunt next year.I was planning on getting a custom turret put on my scope matched to my ballistics. The problem with at I was told is hunting at different elevations. will change my point of impact. One turret setup at !000 feet will shoot over a sheep at 7000 ft and vise versa. Is this true? Is the differance that much? What are my options? I'd really like to have a turret to dial in instead of holding over. Any help?
     
  2. westcliffe01

    westcliffe01 Well-Known Member

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    The most universal turret, that is always correct, is the one sold with your scope, calibrated in MOA or Mils. You print out your drop data, laminate it and take it with you. Verify zero at one of the elevations that match a drop card, then when in the field just use the appropriate drop chart or an application like shooter. Dial the required elevation and windage and your all set.

    Custom turrets are for people who have lots of disposable income. The TV shows don't show you that they probably have 6 turrets for each rifle/load and pick the most appropriate one for the shoot. Most of the shows that show people using them, are also the people making them. If you hunt in the midwest where your elevation is likely to be fairly constant and where the daily temperature is going to be close to the seasonal average, you may be alright. But in the mountains where pressure temperature and elevation are changing day to day, you would need a lot of custom turrets to pick from if they are to be acceptably accurate. Possibly 3 elevations each with 3 temperatures = about as much money as a scope...

    Keep it simple and honest or go big and buy a bunch of them.
     
  3. JohnRP

    JohnRP Active Member

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    I was thinking a turret calibrated in moa would be better. i have know problem shooting it at a local range and figuring out where yardage marks is on the turret but i can't shoot at 6000 ft to figure out my marks. Is there a program where once i figure out drops at sea level i can see what the same marks are on the turret at 2000,3000,4000 etc. I hope you understand what i'm trying to say? Thanks
     
  4. westcliffe01

    westcliffe01 Well-Known Member

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    On this forum, scroll up to near the top of the page. There is a long horizontal menu bar across the top ? Just past half way, there is an item "G7 Ballistic Calculator" You have to sign up, then you can run all the ballistic calculations you want.

    In the end, you are going to use SOFTWARE to calculate a firing solution. The output of the calculation is going to be an elevation and windage correction in MOA. You then dial the required amount of MOA UP and left/right and make the shot. Correcting for wind will be the least certain thing once you have verified the actual ballistics of your load under known field conditions (record temperature and pressure).

    Load development is one thing, and for it to be meaningful, you have to record range conditions when you shoot and measured bullet drop at different ranges and have verified your zero at whatever range you zero it at. If you are able to measure MV, that helps. Otherwise you have to look up the G7 BC for the bullet you are shooting and adjust the MV until it matches your field data. If the manufacturer does not list a G7 BC, then buy Bryan Litz book (Applied Ballistics) that contains a library of bullet data that he personally verified.

    Then when in the field, you have to decide what you are going to use for ballistic calculations. I do not own or use a smart phone, so I got a Kestrel wind meter with the integrated Applied Ballistic software. It has a compass, wind meter, station pressure and ballistic calculator all in 1. But if you have a smart phone you can save yourself some money and download the "shooter" app or the Applied Ballistics app. I use neither, so you will have to wait for feedback from those who do. You will still have to get a wind meter and barometer/station pressure but a less expensive one will do.
     
  5. 300rum

    300rum Well-Known Member

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    SHOOTER or Exbal, iSNIPE.
    all of them have the option of using SIGHT IN Data and Shooting data.

    Example:.

    SIGHT IN DATA
    you sight in your scope at sea level, 45F, 29 inHg

    SHOOTING DATA
    lets say you are at 7000ft elev, 24inHg, -10F on yur sheep hunting trip

    just add all this info and the Shooter will do the correction for you.
    Everybody in this forum are using this future.

    I sight in my rifle 3 years ago and i hunt from prairies foothils and mountains from -20F to +45F temp and the software prediction is right on all the time.
     
  6. Browninglover1

    Browninglover1 Well-Known Member

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    Use a ballistics program to verify your drop data at your current elevation and then use the same information to create a second set of data at the average elevation you will be hunting at.

    The days of taking drop charts with you in the field can be over now that CTS makes custom turret labels that you can apply in the field. You could take labels for every situation you think you could encounter and just apply them before you start hunting for the day. I've been using their labels for a few months now and am absolutely sold on their product.
    Custom Turret Systems | Affordable Custom Turret Labels
     
  7. JohnRP

    JohnRP Active Member

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    Thanks for the reply. I don't have a smart phone either. I'll check into the info posted. Is there that much of a effect between say sea level and 5000ft? Thanks again
     
  8. westcliffe01

    westcliffe01 Well-Known Member

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  9. bruce_ventura

    bruce_ventura Well-Known Member

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    What caliber and load?
     
  10. Clubhunter

    Clubhunter Well-Known Member

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    If I drew a sheep tag, I am buying a G7 BR2 to take with me.
     
  11. JohnRP

    JohnRP Active Member

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    Thats a good video. I'm limiting my shots to 500 yds. I'm shooting a custom 300 win mag with 185 gr berger at around 2960 fps. I have shot a Mt goat but at only 200 yds and I was lucky that the goat was at low elevation. I want to be better prepared. Mountain hunting is a differant ball game then shooting groundhogs at 500yds.
     
  12. bruce_ventura

    bruce_ventura Well-Known Member

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    I calculated the bullet drop in inches for you at two different altitudes and temperatures, for 500 and 800 yd range. This is bullet drop from the muzzle, not from a 100 yd zero.

    Altitude (ft) 1000 ft. 7000 ft
    Range (yds) 500 800 500 800
    59 F -61.0 -180.4 -58.3 -166.8
    0 F -62.4 -188.2 -59.4 -172.2

    The short answer is that you should be fine zeroing and determining ballistics for the turret at a low altitude and hunting at a high altitude at up to 500 yds. The advice you got regarding missed shots applies to longer ranges.

    The altitude change alone causes about 3" difference in bullet drop at 500 yds. You could hold 3" low at high altitude and be fine. If you zero and determine ballistics at low altitude on a hot day, and then hunt at high altitude on a cold day, the difference in drop will be smaller, say about 1-1.5".

    However, I recommend that you make the altitude adjustment in your ballistics before ordering the turret, and calculate the drop adjustment for a middle altitude, say about 4,000 ft. Then the difference between your turret drop and the actual drop will be on the order of 1" or less. Your group size at 500 yds will probably be larger than 1".

    I also recommend using printed turret labels from Custom Turret Systems. I've tried them and they work very well. For example, you could get a set of four labels for range work at 1,000 ft and another for hunting at say 6,000 ft. Total cost would be $50.
     
  13. westcliffe01

    westcliffe01 Well-Known Member

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    As the video shows, you really need to take everything into account. Elevation, temperature, incline and cross wind component. How to do this without juggling too many components is the key. You would do well to make a few attempts at shooting varmints in similar terrain before doing a trophy hunt. With the AB weather station, the only thing I would be missing is the inclination. Of course I am still going to have to carry a rangefinder. So its either a fancy rangefinder + simple wind meter (such as the G7) or a fancy weather station + simple rangefinder.

    For the moment I have no mountains anywhere near me, s I am OK with my solution, but that could quickly change when I move to Colorado.

     
  14. JohnRP

    JohnRP Active Member

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    I really appreciate the info. I was thinking about sending my Leuplod V III 4.5 x14 back to the leupold custom shop and getting a turret like a M1 installed with moa marks than order some custom turret labels and try this set up. i.m getting some labels for my varmit rig too.