What change in moa can I expect?

Discussion in 'Long Range Hunting & Shooting' started by elmerdeer, Sep 29, 2010.

  1. elmerdeer

    elmerdeer Well-Known Member

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    I have my drops tested out 1000 yards, I have a 330 yard zero and my drop in moa at 1000 yards is 20moa, elvation is 400 ft, temp 60 farenheit, and pressure I think was 29.38 in hg.
    Now I am going hunting in Saskatchewan in the end of November, the Temp will probably be around 0 farenheit if were lucky, the elevation will be 1650 ft average, by how much will my drop be affected in moa? And what calculations do I need to do to get to correct my drops?
    I am not sure what the baro pressure will be there? Or is that a standard that depends on altitude?
    Thank you
    Elmer
     
  2. J E Custom

    J E Custom Well-Known Member

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    Cold temperatures will have the most effect because of the ammunition.

    Most people just keep there ammo in there pocket until time to use it unless you have time
    and a place to verify the zeros.

    This is a good place for the detachable Magazine. you can keep it in your pocket and then just snap it in the rifle just befor the shot.

    I allways recomend checking the zero at the site to be hunted but this is not always possible
    so try to maintain conditions that are similar to those at home.

    One thing to check before you go into that kind of cold weather , Remove the firing pin and
    remove ALL grease and oil from it .It wont hurt the rifle and it will assure that you dont have
    grease and oil stiffening up and preventing the rifle from firing. (IT Happens all the time).

    Good luck and stay warm.

    J E CUSTOM
     

  3. Boss Hoss

    Boss Hoss Well-Known Member

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    At 1K knowing the ES is critical---will make the difference in a clean kill and a messy one or a complete miss due to vertical dispersion.

    Also JE is spot on about the bolt!!!!!!! Have seen that one happen.
     
  4. elmerdeer

    elmerdeer Well-Known Member

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    My ES is very good its under 15 avg over all my rounds, I have shot this load at 1000 yards and it has done very well, and my gun is spic and span inside out LOL> You guys are right if anything can go wrong in Saskatchwan it will in those temp!!
    I am just curious about how much of a difference in elevation and those temps would make if my clip is in my poket and my bulltes are warm, I am going from sea level to 1650ft, but those temps will be lower by about 60 dergrees from where I have tested my loads.
    The powder I am using is Retumbo.
    Thanks
    Elmer
     
  5. trebark

    trebark Well-Known Member

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    It's difficult to say how much your velocity will change as a result fo the temperature. Also, tough to say how much your trajectory will changed based on density altitude. Personally, I use Exbal ballistic software. I've done the necessary trajectory validation so that the software is darn close to the actual trajectory. Then, enter my field conditions and it adjusts accordingly.

    Long way to say...use some software and take the guess work out of the equation.

    I was out this past weekend and my software was dialed-in very well out to 1180 yards...

    AAR: Training at CVT with Ed Shell - Maryland Shooters
     
  6. bigngreen

    bigngreen Well-Known Member

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    I shoot my 270 WSM loading with Retumbo in temps from -30 to 90 degrees and I have yet to see any changes due to powder temp with Retumbo. What are you using for drops, a chart or software? If your using charts I would plug them into JBM and then create more charts changing the elevation but using a couple different temps like 0 and 25 degrees.
    In MT during late rifle I can go from 5000ft elevation to 8000ft elevation and 0 in the morning to 30+ degrees during the day in a single day of hunting, it honestly hurts my brain thinking about making charts to figure it all out as apposed to software.
    Good luck :D
     
  7. elmerdeer

    elmerdeer Well-Known Member

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    I am using charts from JBM and my real life drops match my charts at the elvation I tested it at, and I have pluged in all the different numbers of the elavation and temps and I come up wit a 1 moa difference fro 60 degrees at 400 ft to 0 degrees at 1650 ft so I am wondering if thats about right?
    The reason that I have'nt got a software is I only hunt and shoot at 2 different elevations ,sea level and around 1600-1700 ft.
    OH and with Retumbo I also have noticed any velocity change on big temp swings.
    Thanks
    Elmer
     
  8. bigngreen

    bigngreen Well-Known Member

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    My rifle is zero'ed about he same as yours but I use about one more MOA to get to a 1000yrds and I get about a 1.5 MOA difference with mine at 0 degrees and I break even at 35 degrees, so if your already using JBM and have one verified chart you should be GTG. I would shoot where your hunting to verify your higher elevation drop chart and just note any difference and rock on!
     
  9. J E Custom

    J E Custom Well-Known Member

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    To add to my earlier post about the temperature effects on powder. I had a range session
    this past Tuesday and was a little surprised at the results.

    During the summer I had worked up loads for several hunting rifles and had good solid
    zero's at 200 yards. The temperature at the time was in the high 90's and I knew I would
    have to check them before the season arrived.

    Monday a nice cool front moved in and It seemed like a good time to re zero. Temp was In
    the mid 50,s after shooting the first rifle I though something was wrong because the zero
    was almost 3" low. so I broke out another rifle with the same warm weather zero and found
    it to be 2.5 low and after checking all of the rifles that I had worked up during the summer
    I found all of them to be low by an alarming amount.

    These rifles are different calibers and use different powders so the need to verify zero's
    under the conditions to be used is very important.

    When this started I have a 7 STW that has a detachable mag so just to see what effect it
    would have if I stuck it in my pocket and warmed the ammo up.(Actually I placed 3 rounds
    in my pocket and after re zeroing all the rest I loaded them in the mag and shot them as
    fast I could to keep them from cooling off.

    The warm ammo zero was almost perfect as it was during testing in 95o+ and when I
    loaded cold ammo the zero dropped to where it was before and I adjusted to a new POI.

    I tested 5 rifles and they were all low so I am convinced that it makes a difference.

    So If your ammo is going to stay in your rifle and be very cold I would recomend that you
    re zero when you get there if possible. If not, keep the ammo in your pocket untill it is
    time to use it.

    Just more information

    J E CUSTOM
     
  10. elmerdeer

    elmerdeer Well-Known Member

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    Thanks for the update JE, I do have HS mags on my 7mm Dakota and most of the time the bullets will be warm as we are driving around and spotting, and thats where I would get the chance at a long range deer, other than that it will be close range not more than 200yards.
    My concern would be elevation affect on my drops, but all the programs I have used and adjusted them for conditions there only show 1moa difference in drops with elevation, temps, and baro pressure, so even if I am out in the conditions I can adjust for that.
    But soon as I get there I shoot some rounds at 1000 yards just to be sure>
    Thanks for all the feedback!
    Elmer