Range Report G1-G7 difference

[palle2612]

Hi there..

I just noticed that there is a difference in my Bulletflight for Iphone, the diff gets even bigger at longer distance.. Can it be posible that there is 74 cm diff. and 1.3 mRad at 600 meters between G1 and G7.. Havent shoot at that distance yet but going to next month..
G1 shows 5,4 mRad and G7 says 4,1 mRad, it would be nice to know what to expect. I tried loading Brian Litz 167 gr. Lapua. That gave me 5,7 mRad, thats worse than G1, and will not take me past 800 meters on my turret, I can go 1100 meter on standard G7 settings..

 

[azimutha]

Re: G1-G7 difference

That's interesting because converting between the advertised G1 BC of .470 to a G7 BC of .236 (which Ballistic for the iPhone does...and uses the JBM engine) results in the same drop of 4.5 mRad either way given the parameters I entered.

As for Litz' numbers, both his G1 and G7 BCs are considerably lower. They should be considered more accurate, although I thought Lapua did all this sophisticated Doppler stuff. Using his G7 BC I get a drop of 4.7...not as radical as what you're seeing. Note that - if you have access to the book - there is much less variation at different velocities with the G7 measurement than there is with the G1 (.008 vs .068). However, both resulted in the same drop @ 600 yards and varied by .3 mRad @ 1000 yards (10.8") (Sorry these measurements are not metric...just too late and I didn't notice until I looked back at your post).

 

[WusteHase]

Re: G1-G7 difference

Hi, noob here. What exactly is G1 drop? I'm new to this and don't quite understand what the "G#" thing relates to. Sorry for the OT question, but I figured it'd be a good place for it.

 

[Mag 300]

Re: G1-G7 difference

G-1 was an old method of calculating the Ballistic coeff. of projectiles it was never measured and was based off of an old designed less streamlined bullet. G7 is a new designed profile that matches the newer boat tailed more pointed profiles of today
yes the two are largly different but if shooting the new sierra's for example the G7 will be the closest fit and work amazingly well
suggest buying brian's book applied ballistics for $39.95 it will teach you a lot more than you think and give great B.C's for wide range of bulletts

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: WusteHase</div><div class="ubbcode-body">Hi, noob here. What exactly is G1 drop? I'm new to this and don't quite understand what the "G#" thing relates to. Sorry for the OT question, but I figured it'd be a good place for it. </div></div>

 

[Mag 300]

Re: G1-G7 difference

link
http://www.appliedballisticsllc.com/index_files/Book.htm

 

[WusteHase]

Re: G1-G7 difference

Thank you very much. So for the newer BTHP stuff, say a 6.5mm bullet from Hornady or Sierra, I'd want to use G7?

 

[bohem]

Re: G1-G7 difference

Yes, exactly.

Bryan's book is excellent and especially well written for the non-math type readers who wouldn't be able to wade through a ballistic flight textbook.

 

[Lt. Arclight]

Re: G1-G7 difference

Its another that I have to get. I just was reading "New Exact Small Arms Ballistics" by Arthur Pejsa. Which is a good read but if math isn't your thing-I'd say don't buy it.

I didn't realize Bryan Litz was a member here!

 

[Mag 300]

Re: G1-G7 difference

In my opinion <span style="color: #000099">YES</span>
But thats me . the G7 matches the newer bullets very closely
<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: WusteHase</div><div class="ubbcode-body">Thank you very much. So for the newer BTHP stuff, say a 6.5mm bullet from Hornady or Sierra, I'd want to use G7? </div></div>

 

[Mag 300]

Re: G1-G7 difference

We are lucky that he is !!!!!

Bill


<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lt. Arclight</div><div class="ubbcode-body">Its another that I have to get. I just was reading "New Exact Small Arms Ballistics" by Arthur Pejsa. Which is a good read but if math isn't your thing-I'd say don't buy it.

I didn't realize Bryan Litz was a member here! </div></div>

 

[bohem]

Re: G1-G7 difference

<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: Lt. Arclight</div><div class="ubbcode-body">Its another that I have to get. I just was reading "New Exact Small Arms Ballistics" by Arthur Pejsa. Which is a good read but if math isn't your thing-I'd say don't buy it.

I didn't realize Bryan Litz was a member here! </div></div>

I have Pejsa's book as well, and I'm very much a "math-type" but the empirical models that Pejsa uses are not as easy for me to estimate when I'm laying prone trying to estimate dope in my head.

Probably the only reason I can estimate dope as well as I do is because I tend to think in the "radians, first derivative, log regression" format from years of it being beaten into me. Until I read Bryan's methods for doing this stuff I couldn't imagine the "non-math" people ever estimating dope. Now I know how it's completely possible. It's very well done.

 

[40x]

Re: G1-G7 difference

What new ballistic program uses the G7 input and is on a SD card?

 

[Mag 300]

Re: G1-G7 difference

I dont know of one most are a direct download
Anyone ????


<div class="ubbcode-block"><div class="ubbcode-header">Originally Posted By: cpapa</div><div class="ubbcode-body">What new ballistic program uses the G7 input and is on a SD card? </div></div>