balisticians please help

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by kweidner, Sep 10, 2008.

  1. kweidner

    kweidner Well-Known Member

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    Here's the problem. So I am working up a drop chart for my cz 22-250. Ave fps is 3688, extreme spread is 20 fps. My BC was unknown. The bullets are Watson 52 gr. (Ed Watson BR hollow point flat base) I have been working on this for a week or so. I guessed a .350 BC based on the drop at 400 and 500 yds. I shot this evening on quartering winds between 5-10 mph at 565 yds. I used (according to mil dot scope Sightron 6x24x42 Md) a 7.2 MOA shot. (2nd dot). Shots were between 3 and 6 inches low. I adjusted my BC so my drop 64.73 (shot) matched the BC of 3688 fps according to Pesja. My BC ended up at a .308. My adjusted table now shows 64.73 inches of drop at 565 yds. 85 degrees and 200 foot above sea level are my plug ins. This seems like a really high bc for a 52 grain pill. Is my math right? My vertical was less than 4 inches on 10 shots horizontal was 6.5. (gusting winds @ 3:00 and no flags) please help! This rifle, I feel. has great potential.

    Ken
     
  2. Jon A

    Jon A Well-Known Member

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    Here's one minor thing:
    2nd dot will be 6.876 MOA, as each Mil is 3.438 MOA. They are 3.6 inches per hundred yards, which aren't exact MOA.
     

  3. kweidner

    kweidner Well-Known Member

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    JOn you are right. I probably should have included that I have also adjusted MOA on the spreadsheet to be exactly 1 inch. Sorry I over looked this info when stating problem.
     
  4. Jeff In TX

    Jeff In TX Well-Known Member

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    Ken,

    Your guessing with way to many variables and unknowns. Since you have a chronograph, measure an exact 100 yards (not with a laser range finder) and shoot another 10 shot string and get your average 100 yard velocity. Let me know what it is and I'll calculate your exact BC out of your gun. If you can also get your 200 yard velocity average that will really help. I know it sounds crazy to shoot through your chronograph at those ranges, but I've shot through mine at 400 yards in the past which gets real interesting.

    100 and 200 yards is no problem. Also measure your exact scope height.

    Hope it helps
     
    Last edited: Sep 12, 2008
  5. kweidner

    kweidner Well-Known Member

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    I will do that Saturday Jeff. Thank you for your help. Scope is 1.75 centerline to center of bore.

    Ken
     
  6. kweidner

    kweidner Well-Known Member

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    I will do that Saturday Jeff. Centerline of scope to centerline of bore is 1.75"