few questions about a sight-in adjustment

Discussion in 'Long Range Hunting & Shooting' started by Savagebien, Sep 22, 2008.

  1. Savagebien

    Savagebien Well-Known Member

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    alrighty, the deal is i sighted my rifle in back in june when i got my bushnell elite 3200 10x40 MD and all was well. i sighted in with a load of sierra 100gr sbt's and then when i changed to 105 a-max i used the same powder charge and they shot about identical. SO, later on i lessened the powder charge to get more brass life but didnt check my 100 yard zero. and i went and shot at 100 yesterday and today and it was an inch and a quarter low at 100. could this b from the 1.6 grains less imr 4350? i had the drops figured out and shot the load at 860 yards saturday, so now that i had to bring it up 1.25 moa at 100 will all my drops b that much less??? or is it not that simple? thanks for any help!
     
  2. Broz

    Broz Well-Known Member

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    I would say yes, You are 1 1/4 moa higher all the time now. So if you reset your turret to zero. Take 1 1/4 moa off all ranges on your drop chart. But I would do a 600 or 700 yard test to confirm and add confidence in case we are missing something.

    Jeff
     

  3. Savagebien

    Savagebien Well-Known Member

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    alrighty, thanks! i figure thats what i'll do next time i go out!
     
  4. goodgrouper

    goodgrouper Well-Known Member

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    It is very common to have a different point of impact with a different load. However, if you rezeroed your reduced load to have the same POI as the first load, the reduced load will hit lower at long rang due to the reduced velocity. The 1.25 moa up that you added will not factor into your new drop to give you less drop. It is zeroed out and your reduced velocity will make it so you need more MOA up to hit the same targets you were before.
     
  5. Michael Eichele

    Michael Eichele Well-Known Member

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    ALWAYS verify your long range effects including your drops after ANY change even minor changes. A load change of 1.6 grains is enough to at least chrono the new velocity and recalculate known drops with a program then verify in the real world after sighting in for the new load.
     
  6. Broz

    Broz Well-Known Member

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    Guys, I took it all his drop charts were done with the new load and the reduced charge. Then he just re-zeroed at 100 and it took 1 1/4 moa up elevation. So, if this is not correct Savagebien then you do need to re-shoot your drop charts. But like I said, even if I did understand correctly I would still check a few to be sure. After taking off the 1 1/4 moa. You do need to be sure.

    Jeff
     
  7. Savagebien

    Savagebien Well-Known Member

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    the drops taht i had confirmed out to 860 were with this new load.... so yea i'll b checking it all next time i shoot long range :D but will i just have to take the 1.25 MOA off all my drops?
     
  8. Broz

    Broz Well-Known Member

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    Yes, The way I see it you simply raised your elevation turret 1 1/4 moa then loosened the turret and reset it to zero. Correct? If so, you are starting 1 1/4 moa above all you drop chart settings, so take 1 1/4 of each distance setting or you will be 1 1/4 moa high on them all.

    But, like said here before. It never hurts to recheck. Just in case we missed something or the scope didn't track or one many things. Plus, this way you will know for sure and won't miss that 200" Whitetail this November.gun):D
     
  9. Savagebien

    Savagebien Well-Known Member

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    yes indeed, i will do some checking again! just got my bushnell elite 1500 rangefinder too!