Range Report G1 or G7.. I choose G1

P

palle2612

Private
Minuteman
Jun 3, 2008
87
3
52
Denmark. Thats Europe
#1
Hi there..

Last weekend I was on my first real shoot out on a range..
Of course I have been shooting 100 meters but this was a up to 600 meter range a few hours from where I live..

We started out on 100 for zero check, all was fine, went out to 300 meter, checked out my Ballistic FTE on my Iphone, it said 1,5 mRad G1 or 1,5 mRad G7.. Took 1,5 mRad and put 2 rounds on a metal plate and 1 round on the paper.. Bulls eye, that shoot was dead center, made me think if ever wanted to shoot another round that day..But I did..
grin.gif


Made a few groups at 300m before going to 600m. looked at my Iphone, 600 meter 4 a Lapua Scenar 167gr .308 round in G1 said 5,3 mRad and 5,3
mRad in G7. Dialed 5,3 mRad took 2 rounds at the plate with the second one hiting, took a few groups at the paper and checked the groups downrange, elevation was dead on with a few over and under, (was first time, remember) but all in all I was very happy with my shooting..

But now the question is with the above metioned G1 and G7 numbers I really dont see any diff. in the two. Other than if I just changed a G1 BC of .470 into a G7, it made a hell of a diff, then the output was changed from 5,3 mRad to 4,1 mRad.
Should't it convert the BC when changeing Drag!!! I had to manually put in a G7 BC of .238 to make it right..
 
#2
Re: G1 or G7.. I choose G1

I can't speak to how the BC's are implemented in that app, but I can tell you that the practical difference between G1 and G7 predicted trajectories starts coming into play at 600+ yards in most cases. The difference in predicted velocity/energy between G1/G7 is more significant even at the closer ranges which is important when considering minimum expansion velocity and impact energy (hunting applications).

But I can't disagree with your observation; if all your shooting is within 600 meters and you're not looking at retained velocity/energy, you probably won't see a huge difference between G1/G7. I do have to ask, if you see no difference, why would you prefer one over the other (G1 over G7)?

-Bryan
 
#4
Re: G1 or G7.. I choose G1

Applied Ballistics by Bryan Litz explains it in detail.

At the range you were shooting at the bullet is still well in the supersonic range.

If you get ahold of Bryan's book, he has several graphs that are different BC models overlapped. As Lindy stated they deviate greatly as velocities drop off.
 
#5
Re: G1 or G7.. I choose G1, first then got taught.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Bryan Litz</div><div class="ubbcode-body">
But I can't disagree with your observation; if all your shooting is within 600 meters and you're not looking at retained velocity/energy, you probably won't see a huge difference between G1/G7. I do have to ask, if you see no difference, why would you prefer one over the other (G1 over G7)?

-Bryan </div></div>

I don't really fancy one over another... But as a newbe in long range shooting, I would like to keep it simple, meaning that I did not know the G7 BC of my bullet untill I fell over it here on the Hide.. Not knowing the BC in G7 made me think that I just had to press the G7 tap in my program and all would be great, but it wasen't, as I had to find out..
But as you metioned the difference is getting more significant over 600 +, I might end up using it anyway as I plan on going further in time.. And I did not notice the retained velocity/energy thing you mentioned also, Might have to think it over again..

Thanks...
 
#6
Re: G1 or G7.. I choose G1, first then got taught.

It boils down to this...If Bryan says that G7 is better, use G7. The guy knows what he is talking about.

The reason you did not see any difference was outlined above, G7 does not start to shine until past 600 yards. Up to that point, they are going to be very similar.

If you were to buy his book, you would know the G7s of every major projo, highly recommended.

It is a major complaint I have about FTE, that it does not automatially adjust the values when you tell it to use G7, but it does not have all those values, so it is not really possible anyway. To my knowledge, Bryan is the only source on Earth with all the G7 data as most manufacturers do not supply it.

You can always figure the G7 youself too.
 
#7
Re: G1 or G7.. I choose G1, first then got taught.

Re: Ballistic. If you only know the G1 BC, make sure that the "Native Drag Model" is left as G1 and then below that, set "Use Drag Model" to G1. Regardless of whether I switch between its own engine or the JBM engine, it does not do accurate conversions between G1 and G7 BCs. To be fair, I don't know if any program does or not.

As has already been said, if you're not shooting over 600 m/yds and are maintaining high velocities, then G1 will work fine. I'd recommend getting G7 BCs for bullets that fit that model. And, if you want some more accurate ones, consider purchasing Mr. Litz' book. (Hint: the BCs you mentioned for the 1667 gr. Scenar are optimistic).
 
#8
Re: G1 or G7.. I choose G1, first then got taught.

Your g7 differs from Bryan,s average g7 bc that he publishes in his book -a book well worth getting I might add also .If you download the free Lapua ballistics program they raydar test your projectile and you can fiddle with the BC on the Iphone until you equal there out put data -Then test on the range and record your actual data !
 
#9
Re: G1 or G7.. I choose G1, first then got taught.

I would like to get a copy of Bryan's book, but as I am in Europe it would be a mutta.. deal to get it overhere at a good price....
would anyone please tell me why .238 BC G7 is optimistic, I realize if all BC's where public he couldn't sell books, but then PM me..I seem to recall to have read it here on the Hide...
 
#10
Re: G1 or G7.. I choose G1, first then got taught.

I live in New Zealand and ordered the book , it doesn't cost an arm and leg and it has a lot of understandable info in it including G7 BCs - As mentioned if you don't wont to buy the book go to the Lapua web site and down load their free program with the dopplar raydar flight info and manipulate your FTE bc readings to suit
 
#13
Re: G1 or G7.. I choose G1, first then got taught.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: alexzeph142</div><div class="ubbcode-body">How do you determine which G you use at all? What is it and what determines it? </div></div>

The simple answer is that the G1 is better suited to flat bottomed higher drag projectiles. The G7 is tailored to high BC VLD type bullets.

If you want a deeper answer Google or read Bryan's book. I am still trying to wrap my head around the concepts.
 
#14
Re: G1 or G7.. I choose G1

Listen to Bryan!!!!

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Bryan Litz</div><div class="ubbcode-body">I can't speak to how the BC's are implemented in that app, but I can tell you that the practical difference between G1 and G7 predicted trajectories starts coming into play at 600+ yards in most cases. The difference in predicted velocity/energy between G1/G7 is more significant even at the closer ranges which is important when considering minimum expansion velocity and impact energy (hunting applications).

But I can't disagree with your observation; if all your shooting is within 600 meters and you're not looking at retained velocity/energy, you probably won't see a huge difference between G1/G7. I do have to ask, if you see no difference, why would you prefer one over the other (G1 over G7)?

-Bryan </div></div>
 
#15
Re: G1 or G7.. I choose G1, first then got taught.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: LoneWolfUSMC</div><div class="ubbcode-body"><div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: alexzeph142</div><div class="ubbcode-body">How do you determine which G you use at all? What is it and what determines it? </div></div>

The simple answer is that the G1 is better suited to flat bottomed higher drag projectiles. The G7 is tailored to high BC VLD type bullets.

If you want a deeper answer Google or read Bryan's book. I am still trying to wrap my head around the concepts. </div></div>

A little more info on this: If you happen to have the book, both G1 and G7 BCs are listed for each bullet for 1500, 2000, 2500 and 3000 fps, along with averages. Note which BC has the least variation. A Nosler Partition, for example, fits the G1 model better.
 
#16
Re: G1 or G7.. I choose G1, first then got taught.

OK look at G1 this way! Find a picture of a WW1 gas shell. A big fat tube with some kind of short point on the end, 1.5 caliber I think. THIS is a G1 ballistic profile. this is what your computer is digitally flying thru the air to figure out drop etc..
G7 is a SMK or A-max bullet profile.
A very rough description so forgive my crudeness.
 
#18
Re: G1 or G7.. I choose G1, first then got taught.

I was recently helping a shooter with the same type issue. He would use the G1 BC and see good results, then change to the G7 BC and see wacky results. When he asked for my help I took at look at his data. His mistake was using the same G1 drag model for both ballistic predictions. He thought he only needed to change the BC to the new G7 and re-run his calucations. Silly as it sounds, its not the first time I've seen this. It's just understanding how everything works together.

Once he changed and started using the G7 calculations with the G7 BC all was solved and he saw much better results.
 
#19
Re: G1 or G7.. I choose G1, first then got taught.

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: azimutha</div><div class="ubbcode-body">Re: Ballistic. If you only know the G1 BC, make sure that the "Native Drag Model" is left as G1 and then below that, set "Use Drag Model" to G1. Regardless of whether I switch between its own engine or the JBM engine, it does not do accurate conversions between G1 and G7 BCs. To be fair, I don't know if any program does or not.

As has already been said, if you're not shooting over 600 m/yds and are maintaining high velocities, then G1 will work fine. I'd recommend getting G7 BCs for bullets that fit that model. And, if you want some more accurate ones, consider purchasing Mr. Litz' book. (Hint: the BCs you mentioned for the 1667 gr. Scenar are optimistic). </div></div>

I think part of the issue here is converting a single G1 BC to a single G7 BC. If you look at the bullets with multiple G1 BCs, they vary quite a bit. I don't think it's unreasonable to think that a bullet with only a single G1 BC probably varies quite a bit too. So then, you're left with the problem of trying to figure out what velocity is correct for the G1? If you don't know, it's a crap shoot and you might as well use the G1 (in my opinion) since picking the wrong velocity can give you a pretty poor answer.

To me, the real utility in drag function conversion programs is reducing the need for multiple BCs. Take a look at this program:

BC Array Conversion Program

You can put in a multiple BCs of one drag function and have it tell you what is the best single BC and drag function of the input velocity range.

Brad
 
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