G1 vs G7

[MartyK2500]

Which one do you guys use?
I'll have to agree that regular G1 sucks, as I have learned when I started 2 years ago none of my drops would work past 400.
Since then I have imput Sierras multi G1 BC readings in my ballistic app, I have had great success out to 800M with this setup.

Although I am reading Bryan Litz stuff lately, he preaches the G7 data pretty hard.
Let's have a look at Sierras multiple G1 readings from their website :


.308 - 175 SMK
--------------------------------------
.505 @ 2800 fps and above
.496 between 2800 and 1800 fps
.485 @ 1800 fps and below


6.5 - 142 SMK
--------------------------------------
.626 @ 2850 fps and above
.611 between 2400 and 2850 fps
.606 between 2050 and 2400 fps
.581 @ 2050 and below



These are my actual drop charts taken tonight, linked with my Kestrel from the comfort of inside my home, which means 72F, 45% humidity and 29.5 inHG.
I also pretended I had indoor crosswinds of 10MPH.
For the G1 I have used Sierra Bullets multiple BC ratings given on their website, for the G7 I have used Bryan Litz data.

Now if I can add to this, I have never taken my 6.5 out past 300M yet, so I cannot speak for it yet being true to the tables or not.

And my 308 has been shot for an entire season at 900M, using my multiple BC G1 table you see here.
From 200M up to 800M, it was pretty bang on, at 900M my setup was always somewhat sporadic in the elevation department.

So what do you guys think or use, G1 (w/multi BC) or G7?

 

[kthomas]

Modern projectiles generally fit the G7 ballistics profile better then G1. I use either G7 or the Applied Ballistics custom drag curves.

You may have to do a bit of truing go get the ballistics to match up, the farther you can shoot the better for truing, like ~800+ yards. Every rifle is a bit different, so you may need to do a little truing from one rifle to the next.

 

[rugbydave]

Modern projectiles generally fit the G7 ballistics profile better then G1. I use either G7 or the Applied Ballistics custom drag curves.

You may have to do a bit of truing go get the ballistics to match up, the farther you can shoot the better for truing, like ~800+ yards. Every rifle is a bit different, so you may need to do a little truing from one rifle to the next.

This^.

Every projectile I've used in the past few years, if I used good data (MV, etc) and I either inputted a good G7 BC (ask around what others are using) or used the AB custom drag curves my dope has been on out about as far as it will go (I verify at 1500 yards).

 

[MartyK2500]

Up to 800M, my multiple BC G1 is always right without an exception,
In 308 when we compare with G7 readings it’s almost the same.

For 900M where i get sporadic elevations, when looking at G7 tables it says that I’m subsonic, which could be what’s happening.

When you guys speak of custom drag curves, how do you input them in the calculator?

 

[Alpheus]

When you guys speak of custom drag curves, how do you input them in the calculator?

They are part of the ballistic app, not all have them. Applied Ballistics and Hornady 4DOF have them, off the top of my head.

 

[rugbydave]

A G1 or G7 "number" is just basically a modifier of how one specific bullet "flies" compared to a set "perfect" curve on a graph, hence the closer the number is to "1" the better it is. G1 was designed around a flat based projectile and G7 around a boat tailed projectile.

Applied Ballistics "build" custom drag curves for specific bullets by testing them out in the real world with doppler radar. They used to only do it to 300m and then extrapolate from there but I believe I've read that they now test them much further. I believe in practice it's like using a segmented G7 BC (ie different BCs as velocity decays) so it isn't actually a fully custom curve.

Hornady's 4DOF is actually a more advanced solver and doesn't use BC but actually measures, via doppler radar, the bullet's trajectory out to 1000m, I believe.

I've never used 4DOF so although it's theoretically better than AB, in proofing my dope out (and in matches) when using either the AB custom curves or just a correct G7 BC, my dope has lined up perfectly out to 1600 yards (zero target at an elr match I had access to) with my 6mms and 1500 yards (my usual "elr" verification target) with my 6.5 and .308 so I honestly can't ask for much better than that.

With regard to the Kestrel, it's an incredible tool but the only caveat is that most guys don't input a wind speed in wind zone 1 as the AB solver tends to add in too much crosswind/aerodynamic jump and also turn off spin drift and Coriolis as they are also exaggerated. I've found that to be true in my use of the Kestrel as well.