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Chrono vs. Range Dope HELP

 
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  #1  
Old 08-31-2011, 08:51 AM
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Join Date: Apr 2008
Posts: 57
Chrono vs. Range Dope HELP

I have one of these...

Competition Electronics ProChrono Digital Chronograph - MidwayUSA

It says that my 210 Bergers out of my 300 win mag are going 2865 fps. But if I leave the BC alone in the calculator and change the velocity to match range dope, it matches 2805-2810 fps.

I have other field data that the 2810~ matches on gong shooting but while the 875yd data and closer matches... the 1000yd data in .8 MOA less than what the Calculator is putting out.

Any thoughts?
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  #2  
Old 08-31-2011, 10:08 AM
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Join Date: Sep 2004
Location: Nevada
Posts: 569
Re: Chrono vs. Range Dope HELP

bullets don't have a static BC. Some manufactures give the change in BC within velocity ranges. Example is a .560 BC at 2800 + FPS At 2400 FPS the BC is only .530 and at 2000 fps it is now only .500.


So for a long shot you have to get an average BC because of the decreasing BC

I think Sierra bullets lists velocity changes BC's for their bullets.


I've often wondered about aerodynamic changes with a 6 groove barrel over a 3 groove. That is why range BC calculating with real life bullet drop actually shows true projectile BC. Some manufactures list highly overrated BC's for their VLD bullets just to make a sale and the bullets never live up to advertised BC in the field
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.270 Ackley improved 29 inch 1.250 dia. target barrel 7mm STW 28 inch 1.250 target barrel. I also love my .458 mag for varmints and the biggest game in the world.
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  #3  
Old 08-31-2011, 10:35 AM
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Join Date: Jul 2004
Location: Texas
Posts: 5,421
Re: Chrono vs. Range Dope HELP

Quote:
Originally Posted by budlight View Post
bullets don't have a static BC. Some manufactures give the change in BC within velocity ranges. Example is a .560 BC at 2800 + FPS At 2400 FPS the BC is only .530 and at 2000 fps it is now only .500.


So for a long shot you have to get an average BC because of the decreasing BC

I think Sierra bullets lists velocity changes BC's for their bullets.


I've often wondered about aerodynamic changes with a 6 groove barrel over a 3 groove. That is why range BC calculating with real life bullet drop actually shows true projectile BC. Some manufactures list highly overrated BC's for their VLD bullets just to make a sale and the bullets never live up to advertised BC in the field

Very well said !!!!

Both the chronograph and actual drop tables are tools to calculate "TRUE" BCs of a bullet.

J E CUSTOM
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Old 08-31-2011, 10:36 AM
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Join Date: Jan 2007
Location: Ohio
Posts: 163
Re: Chrono vs. Range Dope HELP

If the center of the scope heitgh over the center of the bore has an effect on the drop chart, or a BC ratical. You should field check your drop chart befor you go to the field hunting.
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  #5  
Old 08-31-2011, 10:38 AM
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Posts: 57
Re: Chrono vs. Range Dope HELP

So here is My load:

300 win mag
Nosler Brass
75.5gr of H1000
TOUCHING LANDS
FED 215M Primer
210 Berger HUNTING VLD

GUN:

R700
26" Lilja 3-Groove 1/11" 30cal, #4 Heavy Flutes
HS Precision Stock
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  #6  
Old 08-31-2011, 10:47 AM
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Join Date: Feb 2007
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Re: Chrono vs. Range Dope HELP

Quote:
Originally Posted by Magnum61 View Post
So here is My load:

300 win mag
Nosler Brass
75.5gr of H1000
TOUCHING LANDS
FED 215M Primer
210 Berger HUNTING VLD

GUN:

R700
26" Lilja 3-Groove 1/11" 30cal, #4 Heavy Flutes
HS Precision Stock

Magnum61, I do a lot of work with 300 Win's, 210 Bergers and H-1000 using the old .631 BC as well a the new .616. Just looking at your load and barrel length, If I had to guess I would say your MV should fall into the 2840 to 2860 range. So you might wish to look at second chrono's info. Or simply work it out to your actual field tested drops and don't worry about what the number are. After all they are just numbers. Spot on drops are real and what we seek.

Jeff
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  #7  
Old 08-31-2011, 12:31 PM
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Join Date: Apr 2008
Posts: 57
Re: Chrono vs. Range Dope HELP

I've been using the G7 instead of the G1. Will that make a huge difference?
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