G7 BC

Technical Discussion & Use of BORS

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Terry Ide
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G7 BC

Postby Terry Ide » Wed 08 Jul, 2009 3:45 pm

Will the use of G7 BC work in my Bors calculations???? Berger is now using G7 bc of 242 instead of 473 on the 308 168gr vld. How will this affect my bors????

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Re: G7 BC

Postby Shadow » Thu 09 Jul, 2009 12:51 am

Terry Ide wrote:Will the use of G7 BC work in my Bors calculations???? Berger is now using G7 bc of 242 instead of 473 on the 308 168gr vld. How will this affect my bors????


If the BORS software is based on the G1 BC models, I'd use the .473, but if (by reading your BORS manual) the G7 BC can be used - then use .242. Maybe Shane can get you a better answer.

Anyway, Berger and others (like Sierra) have certainly figured it out and decided not to cave to the "lazer rifle shooters".

Shooting software is available that employs the "Point Mass" method developed with drag functions for most common bullet shapes. Such results are superior to the traditional "G1 fits everything" thinking - but shooters must learn B.C.'s are different for each "G" drag function. This is a scary proposition for bullet companies who understand many shooters pick bullets based on big B.C.'s. For example: A VLD bullet with a G1 based B.C. of .690 will have a properly calculated G7 B.C. of only .344, even though it is a more aerodynamic shape with less drag. I sympathize with the bullet companies. Like trying to explain this to someone who thinks he can make a rifle shoot like a laser, and big B.C.'s are the key? Not reality...

Good luck on your mission....
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Terry Ide
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Re: G7 BC

Postby Terry Ide » Thu 09 Jul, 2009 5:54 pm

Thanks Shadow...........maybe Barrett tec will chime in..............

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Re: G7 BC

Postby Shadow » Fri 10 Jul, 2009 6:28 pm

Barrett Optics Tech wrote:The Barrett Ballistic Software uses the G1 coefficient with the calculated table at a baseline temperature of 60°F and 30inHg.

Please do not attempt to use the G7 coefficient for calculating the drop tables. The results will be well below desirable.


Well, that certainly clears it up. Thanks BOT.

Anyone with a BORS should remember this little tidbit of info. I expect in the future more projo manufacturers will be using the G7 BC numbers, as well as the G1.
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Re: G7 BC

Postby DEDMNKY » Fri 10 Jul, 2009 8:24 pm

Will barrett be making up some software so we could use either the G1 or the G7 BC ?
BARRETT 82A1 SEMI AUTOMATIC WITH LEUPOLD MARK 4 8.2-25X50MM WITH BORS
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Re: G7 BC

Postby ONESHOT » Thu 15 Oct, 2009 2:24 am

Hello.....

If is it possible I would like to know something more about software..
baseline 60° F 30 inHg.......the last one is barometric pressure, for example how the software compensate for different barometric pressure ?
I can be at 5000 ft but with a large spread in barometric values...
I've always used " station pressure " so disregard altitude of my location ( always set at zero )

thanks for replay



Barrett Optics Tech wrote:The Barrett Ballistic Software uses the G1 coefficient with the calculated table at a baseline temperature of 60°F and 30inHg.

Please do not attempt to use the G7 coefficient for calculating the drop tables. The results will be well below desirable.

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Re: G7 BC

Postby ONESHOT » Fri 30 Oct, 2009 6:27 am

thanks for explanations :cheer:


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