G1 vs G7

[med358-boise]

I was using the Hornady ballistic calculator and with G1 @ 800 yds with .450 bc my MOA adj is 18.1. Using the same BC and G7 its 13.5.
If I reduce the BC to .27 at 800 yds my adjustment is 16.3. My initial thread was using the same BC for G1 and G7 which is why the difference.
I ran your number on the Hornady calculator and got 19.9 for G1 and 20 for G7. Remember the 180 has a higher BC than the 168.

Yes, but to re-emphasize G1 and G7 are completely different formulas and "metrics". Its almost like saying I had a formula written for lbs per sq in of torque then input that value into another formula that was looking for nanometers of torque as a variable and then wondering why I got a weird answer.

 

[memtb]

I would add that all published BCs are just that published BCs will be slight different in every rifle based on velocity and some other factors. Therefore to be very accurate - you zero @ a distance usually 100 then shoot and document actually drop several 100 yards further and then record your drops. Then inpour actual drops and either manual manipulate BC or some programs will calculate the "true or correct" actual BC.

This somewhat addresses another topic on this forum, "zero range", which helps me justify my position on that topic.


Using your statement- I would add that all published BCs are just that published BCs will be slight different in every rifle based on velocity and some other factors


With my 300 yard zero, and the assumption that there will be small discrepancies as distance is increased, starting out with a 300 yard zero and my limited, self-imposed maximum shooting distance on game ……should somewhat reduce those discrepancies at my maximum distances.

Meaning ……I should be closer to my desired point of impact at 600 yards with my 300 yard zero, than I would be with a 100 yard zero, when atmospheric changes will undoubtedly affect the factory stated bc! memtb

 

[Clem Bronkoski]

This somewhat addresses another topic on this forum, "zero range", which helps me justify my position on that topic.
With my 300 yard zero, and the assumption that there will be small discrepancies as distance is increased, starting out with a 300 yard zero and my limited, self-imposed maximum shooting distance on game ……should somewhat reduce those discrepancies at my maximum distances.
Meaning ……I should be closer to my desired point of impact at 600 yards with my 300 yard zero, than I would be with a 100 yard zero, when atmospheric changes will undoubtedly affect the factory stated bc! memtb

I don't think so memtb. You still have to shoot to determine actual drop. Even your own statements above enforce that...an assumption and should won't put you on target. Even 1 MOA difference at 800 yards would be a complete miss on a deer. Heck a dead center hold at about 550 yards with one MOA error would be a complete miss. Practice and shooting at varying distances are the only true ways to tell where your bullet is going to land.

 

[memtb]

I don't think so memtb. You still have to shoot to determine actual drop. Even your own statements above enforce that...an assumption and should won't put you on target. Even 1 MOA difference at 800 yards would be a complete miss on a deer. Heck a dead center hold at about 550 yards with one MOA error would be a complete miss. Practice and shooting at varying distances are the only true ways to tell where your bullet is going to land.

I think that the error percentage while remaining the same, will be less when only effected on a much shorter distance downrange from the 300 yard verified zero.

Let's assume, pulling this out of space, a 1% error on the BC for the previously mentioned reasons. 1% error is significantly less over a distance of the 300 to 600 yards, which is my shooting range limit on game……than would be that same 1% error, starting at 100 yards! JMO.


Practice at various ranges, means little if atmospheric variables are not the same as practice shots. If I could only be certain that the desired animal will continue to stand there while I verify my bullet drop at those atmospheric conditions as compared to a previous shooting foray under different conditions! memtb

 

[cohunt]

Get a ballistic app- most of them have a database of bc's

 

[std7mag]

Distance, yards​	Elevation, inch​	Elevation, MOA​
100.0​	D0.0​	D0.0​
200.0​	U2.2​	U1.1​
300.0​	U9.2​	U2.9​
400.0​	U21.7​	U5.2​
500.0​	U40.7​	U7.8​
600.0​	U67.1​	U10.7​
700.0​	U102.6​	U14.0​
800.0​	U148.4​	U17.7​
900.0​	U206.5​	U21.9​
1000.0​	U280.3​	U26.8​

 

[std7mag]

200 yard zero.

​	​
​	​
​	​
​	​
​	​
​	​

Distance, yards​	Elevation, inch​	Elevation, MOA​
100.0​	D1.1​	D1.1​
200.0​	D0.0​	D0.0​
300.0​	U5.9​	U1.9​
400.0​	U17.3​	U4.1​
500.0​	U35.2​	U6.7​
600.0​	U60.5​	U9.6​
700.0​	U94.9​	U12.9​
800.0​	U139.5​	U16.7​
900.0​	U196.6​	U20.9​
1000.0​	U269.3​	U25.7​

 

[std7mag]

Sorry, got kinda messed up with copy & paste.

 

[Clem Bronkoski]

I don't know what variables you're inputting but your results are different than what I'm seeing. Close but not the same.

 

[waveslayer]

Or use AB and scratch the G1 and G7 data and use CDM. CDM is the actual drsg model for each bullet

 

[Beluebow]

Roughly..

G1 x .512=G7
G7/.512=G1

 

[Josh06]

Getting into this LR stuff and reading a lot about ballistics I read where an individual should use the G7 BC when shooting long range type bullets. The manufacturers that list both G1 and G7 are few but I observed that the G7 BC is always significantly lower than the G1 BC. My problem is not all manufacturers list the G7 BC so how do you input data when you don't know what it is.
Example: I ran the same data through a ballistic calculator using the same BC for both G1 and G7 for my 300WM load with Barnes TSX bullets and even at 300 yards I noticed a difference and this difference became wider as the range increased to the point that at 800 yds it was 18.1 MOA for G1 and only 13.5 for G7.
That's a drop difference of just about 37" !!
Looking at some of the bullets that list both I took 60% of my bullet's BC and plugged it in and came closer to the G1 data.
Is there a way to more accurately calculate the G7 BC because most of the time I shoot without a spotter and getting close to my target is critical. I may be able to identify a hit 3' off depending on conditions but not always.
Am I splitting hairs here or not. I realize I have to do my own shooting to determine what my actual drops are at varying distances.

I think you have another error. I use a Garmin Tactix 7 and can easily switch between G1 and G7 so just checked my last range from my last shooting session which was 631 yards. My 75 eldm profile is 8.44 moa with G1 and 8.25 moa with G7. With 147 eldm it's even closer at 14.53 GI and 14.43 G7.

 

[Clem Bronkoski]

I think you have another error. I use a Garmin Tactix 7 and can easily switch between G1 and G7 so just checked my last range from my last shooting session which was 631 yards. My 75 eldm profile is 8.44 moa with G1 and 8.25 moa with G7. With 147 eldm it's even closer at 14.53 GI and 14.43 G7.

Josh I appreciate your input and with my input data I am similar using G7. (I'm assuming you meant 175 ELDM not 75). At 600 I get 8.7 and at 650 I'm 9.8 so we're in the same ball park. Your ELD-M likely has a higher BC. Of course actual shooting is needed to verify POI.

 

[Clem Bronkoski]

Admin I think we've beat this dead horse long enough. Thanks guys