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# G function question

#1
10-11-2004, 08:52 AM
 Silver Member Join Date: Feb 2004 Location: Wisconsin Posts: 323
G function question

two bullets: berger 7mm 180gr VLD, berger 30cal 210gr VLD.
two trajectories:

1. mv3000, BC .698, weight 180gr, zero 200yrds, max range 2000yrds, increment 100yards, humidity 75%, altitude 1000. All otheres default.

2. mv3000, BC .640, weight 210gr, zero 200yards, max range 2000, increment 100yrds, humidity 75%, alt 1000. All others default.

trajectory 1 using default G function (g1) - @2000 yards: drop = -1680, windage =274.5

trajectory 2 using default G function (g1) - @2000 yards: drop = -1851.3, windage = 308.5

trajectory 1 using G 7 function - @ 2000 yards: drop = -1009, windage = 105.3

trajectory 2 using G7 function - @ 2000 yards drop = -1051, windage = 117.9

Which is right? Note: I've used 2000 yards because it shows the greatest difference for ease of learning purposes.

Also...

Is the 240gr. sierra match king considered a VLD...what g function to use?
Is the 300gr. sierra match king considered a VLD ...what g function to use?
#2
10-11-2004, 09:37 AM
 Silver Member Join Date: Aug 2003 Posts: 126
Re: G function question

The published BCs that you enter are G1. The G7 (or other) might be more appropriate for a particular bullet. If you want to use G7, you must convert your BC. You can't use the G1 BC. People like to quote the G1, since it tends to be the largest.
#3
10-11-2004, 09:39 AM
 Silver Member Join Date: Feb 2004 Location: Wisconsin Posts: 323
Re: G function question

sovles that. Thanks. [img]images/icons/smile.gif[/img]
#4
10-13-2004, 03:10 PM
 Silver Member Join Date: Aug 2003 Location: McKinney TX Posts: 408
Re: G function question

Sierra matchkings are truly boattail bullets and not VLD. They would use a G5 drag model, which was developed for boattails and not the G7, which was developed for VLD bullets.

I used my RSI ballistic program, which will convert bullet drag functions. I can also take the bullets dimensions and plug them into a drag model estimator, which will tell you what drag model is correct. The sierra boattails definitely fall under the G5 drag model.

240gr. sierra match king G1 BC is .711 converted to G5 is .411

300gr. sierra match king G1 BC is 768 coverted to G5 is .477

Hope it helps
__________________
Jeff

Mathew 5:16

Distance is not an issue, but the wind will make it interesting!

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