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few questions about a sight-in adjustment

 
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  #1  
Old 09-22-2008, 02:04 PM
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few questions about a sight-in adjustment

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!
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Old 09-22-2008, 02:20 PM
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Re: few questions about a sight-in adjustment

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
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Old 09-22-2008, 02:22 PM
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Re: few questions about a sight-in adjustment

alrighty, thanks! i figure thats what i'll do next time i go out!
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Old 09-22-2008, 07:19 PM
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Re: few questions about a sight-in adjustment

Quote:
Originally Posted by Savagebien View Post
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!

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.
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Old 09-22-2008, 07:28 PM
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Re: few questions about a sight-in adjustment

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.
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Old 09-22-2008, 07:45 PM
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Re: few questions about a sight-in adjustment

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
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  #7  
Old 09-23-2008, 02:30 AM
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Re: few questions about a sight-in adjustment

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 but will i just have to take the 1.25 MOA off all my drops?
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