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drop chart and chronograph drop chart

 
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  #1  
Old 10-21-2011, 08:39 PM
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drop chart and chronograph drop chart

Hey fellas, I recently got a pro chrono digital and the speeds that my chrono reads are roughly 100 fps difference than my actual drop data chart..is this pretty typical (i know there alot of factors that play a part, I was just a little suprised in the difference)
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Old 10-21-2011, 09:03 PM
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Re: drop chart and chronograph drop chart

miss read your question

Last edited by highridge1; 10-24-2011 at 09:25 PM.
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Old 10-21-2011, 09:07 PM
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Re: drop chart and chronograph drop chart

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Originally Posted by highridge1 View Post
You have to build your drop chart based on what the chronographs says. If your drop chart is 100 fps different just make another drop chart that is correct.
Yep and keep in mind that the chrono only gives you the actual speed at that point in flight.

Listed BC's and actual BC's are two different things as well which is why you can build your drop chart according to the MV, and still not be correct at longer ranges. BC changes as velocity changes.

Start with the MV as verified by the chrono, then verify drops at 3 different ranges such as 200, 400, 600, or 300, 600, 900 and adjust the BC to fit the actual data and then you can have a precision drop chart that will have you plus/minus just a few inches at any range.
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Old 10-22-2011, 12:26 AM
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Re: drop chart and chronograph drop chart

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Originally Posted by WildRose View Post
Yep and keep in mind that the chrono only gives you the actual speed at that point in flight.

Listed BC's and actual BC's are two different things as well which is why you can build your drop chart according to the MV, and still not be correct at longer ranges. BC changes as velocity changes.

Start with the MV as verified by the chrono, then verify drops at 3 different ranges such as 200, 400, 600, or 300, 600, 900 and adjust the BC to fit the actual data and then you can have a precision drop chart that will have you plus/minus just a few inches at any range.

Ok, so if i'm understanding this right..i have my true drop chart..and i'll do a trajectory validation say 500 yards 7moa..and i'll switch my BC until it shows the velocity that my chrono was reading?? Doing it that way I got a BC of .890 ???
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Old 10-22-2011, 12:37 AM
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Re: drop chart and chronograph drop chart

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Originally Posted by sdriverbottom View Post
Ok, so if i'm understanding this right..i have my true drop chart..and i'll do a trajectory validation say 500 yards 7moa..and i'll switch my BC until it shows the velocity that my chrono was reading?? Doing it that way I got a BC of .890 ???
No you adjust your BC until it's reflective of your true drops.

You start with the MV from your chrony in your initial calculations.

Take your advertised BC, your MV, plot your drops.

Then, look at the difference in your drops and what the program spits out and adjust the BC until you have it reading true.
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Old 10-22-2011, 12:50 AM
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Re: drop chart and chronograph drop chart

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Originally Posted by WildRose View Post
No you adjust your BC until it's reflective of your true drops.

You start with the MV from your chrony in your initial calculations.

Take your advertised BC, your MV, plot your drops.

Then, look at the difference in your drops and what the program spits out and adjust the BC until you have it reading true.
Alright I believe I have it down now..I started with my chrono MV (3023) and then adjust my BC to match that drop chart with my field proven true drop chart

Last edited by sdriverbottom; 10-22-2011 at 12:51 AM. Reason: error
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Old 10-22-2011, 03:47 AM
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Re: drop chart and chronograph drop chart

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Originally Posted by sdriverbottom View Post
Alright I believe I have it down now..I started with my chrono MV (3023) and then adjust my BC to match that drop chart with my field proven true drop chart
Great. Now take it out and shoot it at some random distances where you didn't do your test shots and you should find it to be very, very close.
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