Where is 600yd POI likely to move to????

Discussion in 'Long Range Hunting & Shooting' started by T3-OleMan, Jun 5, 2011.

  1. T3-OleMan

    T3-OleMan Well-Known Member

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    Please give me your most educated projection of where my POI will be in NOV for the 600 yd “pin-bar” @ 600 yds. when I go from 562' elev. in S.C. to 10,000' in CO and Tep. drops from 92 deg F to 10 -15 deg F. & your reasoning. (same conditions -no wind and BlueBird Day).
    All our ranges are 100 yds. So I begged a farmer friend, he had a SAFE 610yd. Pasture.

    18th year to same Mt.range in CO and I only have a 5% chance of a > 350 yd shot. But I want to get a feel for what the change should do!

    Givens:
    Rifle: Tikka T-3 SS Lite 338WM – 24” 1-10R, no brake, no bipod.(LOVES Dirty barrel >l0 < 30).
    New Scope: Zeiss Victory FL Diavari 4-16x50T* with Rapid Z 800 Ret-(Ran a Zeiss zoom prog. And it came up with 14.76X = zero at 600 on 600 yd bar)
    Ammo: Hornady GMX 185gr Superformance factory @3,080 fps. Advertised. (total 40 rounds-this ammo-total gun rounds 250 ish.)

    4” between last 2 rounds @610 yds.!! Last round was 1” right and 1/4” down, pure luck.. With all the experience on here a bunch of you will have an opinion. Thats' all I want. What can I reasonably expect?? We ain't talking about me doing my part...just what the 185gr GMX @3,080 fps will do different.

    Thanks


     
  2. SBruce

    SBruce Well-Known Member

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    Not a guess, but right out of the ballistic program.
    Assuming 100 zero and standard atmosphere at both elevations, input the temp at both elevations, used 92 and 12.

    The program gave 71.4" low and 11.25 moa at home
    The program gave 64.6" low and 10.25 moa on the mountain.

    If it were me, I'd still want to confirm a 100yd zero on the mountain and try a rock or something at 600 using the computer generated 10.25 moa holdover just to make sure. With your reticle, I believe you could use the full 16X for 600yds when on the mountain (if I did the math correctly). I am reverse calculating the 600 yd line is 10.5 moa low when on 16X...??

    This is purely hypothetical and based on math and ballistic program. I've personally never went from one such extreme to another and shot, so I don't have any real world info for that. I have seen zero's change just in a few thousand feet of elevation though. I be thinking the extreme change in temps would also have an effect on velocity, maybe a small one, but I would expect it nonetheless.
     

  3. BuckSnort

    BuckSnort Well-Known Member

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    I just ran the same numbers SBruce did through my Shooter Droid App and came real close to his MOA.... only .25 MOA more for both locations...
     
  4. SBruce

    SBruce Well-Known Member

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    The program I used rounds the moa correction to the nearest .25 moa. Does the Shooter app do the same thing, or round up to the next .25 moa? Just curious, never used that one.
     
  5. BuckSnort

    BuckSnort Well-Known Member

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    Yes, same way... to the nearest .25.... Really cool app so far, hope to get to use in on a high country buck this fall...:)
     
  6. BuckSnort

    BuckSnort Well-Known Member

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    SBruce, I must have had a brain fart earlier ...it goes to the nearest 1/10 of MOA....
     
  7. SBruce

    SBruce Well-Known Member

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    Glad you mentioned that, I now see that mine will go 1/10 also, but I have to change the settings under "sight adjustment options". Default is closest 1/4 minute.
     
  8. T3-OleMan

    T3-OleMan Well-Known Member

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    Thanks for the input. This morning I ran the Hornady Ballistics Calc. for Home and 10 F @ 10,000'
    as well as the ZEISS Rapid Z 800 for the 10 F @ 10,000' and came up with the same # yall did, one MOA less.

    Am I correct in reading yours and my MOAs a perfect shot by me -using my 600yd bar, at current calabrations - would hit approx 6” high at 600 yds?


    Additional GIVENS:
    1. MOA is in 1/3”
    2. I picked the Diavari 4-16x50 and the Rapid Z 800 so I could Long Range Hunt ( 338WM _ 400yd to 800 max.) without doing the knob clicks!
    3. All I do is run the Zeiss long range analysis prog. for various Temp.F and Altitudes' and hunt with the Optimum Power settings and all my bars will be Zero within +- 13 yds of that distance for 300 bar through 800bar with 600 bar being ZERO.
    EXAMPLES: @10,000ft

    10 F / Optimum Power 14.96x .....................................50 F / Optimum Power 15.17x
    Bar 3 zero = 295yds ........................................................Bar 3 zero = 295yds
    Bar 4 zero = 396yds ........................................................Bar 4 zero = 395yds
    Bar 5 zero = 497yds ........................................................Bar 5 zero = 496yds
    Bar 6 zero = 600yds ........................................................Bar 6 zero = 600yds
    Bar 7 zero = 705yds ........................................................Bar 7 zero = 706yds
    Bar 8 zero = 811yds ........................................................Bar 8 zero = 813yds

    I hunt 95% Dark Timber 9k' to 11k' with a few small medows. My scope is on 4x to 6x to get off a quick shot on any bumps. When I do a rest day for my old bones and other parts I plan to go to an area 6-7 miles away and climb to 10k and sit in a chairblind and glass several openings for an hour or so, then move to new areas.

    If~n fumble fingers and brain farts don't get in the way.....ALL I GOT TO KNOW IS RANGE (I use a Nikon Lazer 800) & I'm GOOD TO GO........I Pray I can do my part!


    Thanks again.
     
  9. rscott5028

    rscott5028 Well-Known Member

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    I guess I'm not familiar enough with Zeiss, but how do you distinguish between 14.96x and 15.17x?

    Why not print a range card that works with the scope at full power?

    You may also want to consider the termperature stability of your powder as most ballistics programs work off of the stated muzzle velocity.

    -- richard
     
  10. SBruce

    SBruce Well-Known Member

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    Yes, basically. According to the program, you'll hit about 7" high and a 10 mph crosswind will blow the bullet off 7" less than at home at 600 yds.

    rscott5028 makes a good point in that it could be hard to tell exactly what power you're on. Pehaps you could shoot full power at home and record where you're hitting. Then you can subract 7" from that number (at 600 yds) for when you're on the mountain. Program says subtract 4" drop/5" wind for 500 yds, 2" drop/3" wind at 400.
     
  11. T3-OleMan

    T3-OleMan Well-Known Member

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    Thank you richard
    .......................................................................................................................



    Thank you SBruce
     
  12. rscott5028

    rscott5028 Well-Known Member

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    You can run all the calculations and theories here that you want.

    You can go to the range and practice all kinds of scenarios.

    But when that trophy presents itself in the field, there usually isn't time to fumble around.

    So, KISS. ...keep it simple stupid

    Happy hunting!
    -- richard
     
  13. fatrack

    fatrack Well-Known Member

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  14. T3-OleMan

    T3-OleMan Well-Known Member

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    Thanks fatrack:D I owe you one!:cool:

    UPDATE on Superformance powder Sensitivity!

    Last month Hodgdon told me that my Hornady 338WM -185GMX Superformance ammo that has MV 3,080fps on the box will shoot MV 2,997fps at ZERO F! That is because the 3,080 was shot at 70 F......that is a loss of 83 fps in the 70 degree drop!
    Here are my questions:

    Would you assume it to be a LINEAR change for my calculations of speed at 10F, 20F, 30F, 40F etc.......= +11.857fps for each 10 degree change???

    IF ZERO F is 2,997fps and 70 F is 3,080fps 90 F should be what....? 3,104fps.

    And lastley, lightbulbI think this new speed change will remove that 7" high that I was going to have to adjust for when I went from S.C. 592' Elev. and 90 F to 10,000' and zero F???? What do you think? Am I Good to Go?