Does anyone know of a formula to convert G1 to G7 B.C.? I want to convert the Hornady 7mm 162 grain A-Max in particular. Thanks in advance.
Mark
Mark
- Thread starter Raven 6
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Re: G7 to G1 Conversion
I don't know of any formula to convert but there are some numbers published for the AMAX in question as well as some background information in this thread: http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=1962678
The Hornady site lists 0.625 as the G1 value. The number in the thread is different with explanation... i.e. G1 BC .599 and G7 BC .307
I don't know of any formula to convert but there are some numbers published for the AMAX in question as well as some background information in this thread: http://www.snipershide.com/forum/ubbthreads.php?ubb=showflat&Number=1962678
The Hornady site lists 0.625 as the G1 value. The number in the thread is different with explanation... i.e. G1 BC .599 and G7 BC .307
Re: G7 to G1 Conversion
most ballistic calculator offer the option to choose which "G" to use.
most ballistic calculator offer the option to choose which "G" to use.
Re: G7 to G1 Conversion
Why?
You probably have the wrong reasonings. Most likely a incorrect understanding given the request for a "conversion".
Hornady G1 .625
Litz G1 3000fps .633
Litz G1 AVE .599
Litz G7 AVE .307
Litz:
FPS G7 G1
1500 .305 .549
2000 .303 .602
2500 .309 .614
3000 .310 .633
Why?
You probably have the wrong reasonings. Most likely a incorrect understanding given the request for a "conversion".
Hornady G1 .625
Litz G1 3000fps .633
Litz G1 AVE .599
Litz G7 AVE .307
Litz:
FPS G7 G1
1500 .305 .549
2000 .303 .602
2500 .309 .614
3000 .310 .633
Re: G7 to G1 Conversion
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: George63</div><div class="ubbcode-body">simply put:
The G7 is a much better BC modeling for this modern projectile than the G1 </div></div>
Sure, however the "much" depends on the conditions all-else-equal. The printed difference being most significant at velocity boundary conditions or velocity extremes. Velocities near and under 1500fps more often being the most significant. Hmm, these velocities are exhibited far down range where all the external environmental variables and errors in ballistic modeling and calculation are also the most significant.
How far is the OP shooting and how good are the inputs?
BC (G1,G7) is a number supplied based on velocity condition(s) and multiple sources. In either case, consider the source and condition.
1) Are published BC values available in velocity step?
2) Is it a single BC and at what test velocity? (ex: 3000fps common)
3) Is the user taking a single G1 or G7 value (often banner or optimal) and intelligently applying an average estimate if printed stepped BC values are not available?
Run Litz’s published G1 and G7 values (tested in same method, step or average) for the OP at 500yards and then 1000 under generic conditions. What do you see? Not to underplay Litz’s G7 work. It can provide both G1 and G7 values under the same test conditions and at multiple velocities where some bullet manufacturers do not.
The G1 vs G7 value is ultimately dependent on validity and use. When either is accurate, the ultimate results are still significantly dependent on all the additional inputs to produce an estimated trajectory. G7 is a better overall standard model. It’s still a number or numbers stuck into the same calculators along with many other numbers.
Litz’s book is a great buy and reference.
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: George63</div><div class="ubbcode-body">simply put:
The G7 is a much better BC modeling for this modern projectile than the G1 </div></div>
Sure, however the "much" depends on the conditions all-else-equal. The printed difference being most significant at velocity boundary conditions or velocity extremes. Velocities near and under 1500fps more often being the most significant. Hmm, these velocities are exhibited far down range where all the external environmental variables and errors in ballistic modeling and calculation are also the most significant.
How far is the OP shooting and how good are the inputs?
BC (G1,G7) is a number supplied based on velocity condition(s) and multiple sources. In either case, consider the source and condition.
1) Are published BC values available in velocity step?
2) Is it a single BC and at what test velocity? (ex: 3000fps common)
3) Is the user taking a single G1 or G7 value (often banner or optimal) and intelligently applying an average estimate if printed stepped BC values are not available?
Run Litz’s published G1 and G7 values (tested in same method, step or average) for the OP at 500yards and then 1000 under generic conditions. What do you see? Not to underplay Litz’s G7 work. It can provide both G1 and G7 values under the same test conditions and at multiple velocities where some bullet manufacturers do not.
The G1 vs G7 value is ultimately dependent on validity and use. When either is accurate, the ultimate results are still significantly dependent on all the additional inputs to produce an estimated trajectory. G7 is a better overall standard model. It’s still a number or numbers stuck into the same calculators along with many other numbers.
Litz’s book is a great buy and reference.
Re: G7 to G1 Conversion
I appreciate everyone's input. I had the numbers wrong, I want to convert from G1 to G7 not the other way around. After reading quite a bit of the new Berger reloading manual it makes perfect sense to use the G7 co-efficient with modern bullets. I am planning on shooting a 7-08 using the bullet mentioned earlier to ranges out to around 1,000 yrds. I know in the Berger manual it states Litz's book being for sale and that he has put the G7 co-efficient in it for many modern bullets not just Berger. But being the pessimist I am my luck I would buy the book and the one I'm looking for wouldn't be in it. So thus the question, is there some formula or way of converting one to the other. I'm open to ideas or suggestions if they are valid ones.
Mark
I appreciate everyone's input. I had the numbers wrong, I want to convert from G1 to G7 not the other way around. After reading quite a bit of the new Berger reloading manual it makes perfect sense to use the G7 co-efficient with modern bullets. I am planning on shooting a 7-08 using the bullet mentioned earlier to ranges out to around 1,000 yrds. I know in the Berger manual it states Litz's book being for sale and that he has put the G7 co-efficient in it for many modern bullets not just Berger. But being the pessimist I am my luck I would buy the book and the one I'm looking for wouldn't be in it. So thus the question, is there some formula or way of converting one to the other. I'm open to ideas or suggestions if they are valid ones.
Mark
Re: G7 to G1 Conversion
Mark the number itself tells you very little, it's where you plan to use it that matters the most.
If you use a point mass solver it's a bit more accurate with G7, using the published average. These solutions are BC dependent, and were written to favor G7, unless you band the BC.
See, if you band the BCs, the solution and the amount work is the same. Doesn't matter which BC you use. It will adjust to adapt and work well out to distance.
Some programs will band the G1 for you from the start providing a good solution. The benefit of the G1 is the long history and proven success. Plus the numbers are everywhere you look. As you have discovered, getting a G7 BC is a bit harder to come by.
Taken further, the two best programs on the market don't use point mass as a solver so the solution does not care which BC model you use. And of the two best only one even uses G7, the other sees no reason to use it and is very accurate without G7. So understand its the method and not the number. You can easily reach the same point no matter which model you use.
It's getting better, finding the G7 numbers, but don't dismiss the history of G1. It's been finessed so well the numbers are hard to beat.
Mark the number itself tells you very little, it's where you plan to use it that matters the most.
If you use a point mass solver it's a bit more accurate with G7, using the published average. These solutions are BC dependent, and were written to favor G7, unless you band the BC.
See, if you band the BCs, the solution and the amount work is the same. Doesn't matter which BC you use. It will adjust to adapt and work well out to distance.
Some programs will band the G1 for you from the start providing a good solution. The benefit of the G1 is the long history and proven success. Plus the numbers are everywhere you look. As you have discovered, getting a G7 BC is a bit harder to come by.
Taken further, the two best programs on the market don't use point mass as a solver so the solution does not care which BC model you use. And of the two best only one even uses G7, the other sees no reason to use it and is very accurate without G7. So understand its the method and not the number. You can easily reach the same point no matter which model you use.
It's getting better, finding the G7 numbers, but don't dismiss the history of G1. It's been finessed so well the numbers are hard to beat.
Re: G7 to G1 Conversion
Lowlight would you divulge the two programs you are referring too? Keep it coming guys, there is no such thing as too much information.
Lowlight would you divulge the two programs you are referring too? Keep it coming guys, there is no such thing as too much information.
Re: G7 to G1 Conversion
ColdBore
Field Firing Solutions
ColdBore
Field Firing Solutions
