Truing the solver

[Gila]

I have a new custom barrel paired with a tikka action. I put the rifle together in June and have worked up a load for it that I am going to use for Elk. I have a sample size of about 80 rounds. The sweet spot was 2900 fps and I sent about 50 rounds out to 200 and the groups have been very good. For now, I am going to limit my shots on game to 500 yards until I can build confidence in the rifle and load. I am going to use holdover or dial turrets depending on the shot I am presented with. Therefore I have sighted in at 200 yards for now.

I have the AB engine in my range finder. I trued that solver to 571 yards. The range finder gave me up 8.6 MOA. I was consistently 6 inches high. I had to increase the muzzle velocity to 3000fps and settled for 7.8 MOA to get the groups (about 4 inches) around center. I did expect (or at least had hoped) that the new barrel would speed up about 60fps but 100fps seems excessive? I backed down to 300 yards and the groups were still good and around center.

 

[WKR]

Double check all your inputs, and that you entered a 200 yard zero not a 100 yard zero.

 

[The Guide]

Have you tried a different ballistics calculator to see if it gives you the same dope?

Jay

 

[z987k]

How sure are you of the BC of the bullet? If you have measured muzzle velocity, it's not that.
If you haven't then verified BC with drops, then you have an estimated BC.
I'd put it through the chrono again and check that first.

 

[SDHNTR]

Zero at 100. It’s easier to verify. Then double check your MV again. Be sure to get an average over at least ten shots.

 

[Wrench]

A few things....

Tall target test is done. Did you come up at 1.0/1?

Did you input tmoa or smoa?

I agree with zero at 100 and just roll the 1.5 on in the field.

Do expect the velocity to pick up a bit too as it burns in.

 

[Gila]

Have you tried a different ballistics calculator to see if it gives you the same dope?

Jay

I was using Strelok Pro for years and liked it but needed an update and couldn’t get it because the app is sanctioned. The bullet is Hornady, tried 4DOF but didn’t work with my WeatherFLow very well. So i paid for GEO and it works well….I tried plugging in the same MV in both but the elevation is different. I will need to check the variables and rifle profiles of both and try to nail down the differences. I am using the G1 provided on the bullet box. I will run it through the chrono to see if the barrel has gained some speed.

 

[The Guide]

I was using Strelok Pro for years and liked it but needed an update and couldn’t get it because the app is sanctioned. The bullet is Hornady, tried 4DOF but didn’t work with my WeatherFLow very well. So i paid for GEO and it works well….I tried plugging in the same MV in both but the elevation is different. I will need to check the variables and rifle profiles of both and try to nail down the differences. I am using the G1 provided on the bullet box. I will run it through the chrono to see if the barrel has gained some speed.

This is a basic calculator that will get you close with basic inputs. Give it a try and see if it gives you the same solution.

Jay

Ballistics Calculator

The Berger Bullets Ballistics Calculator uses BCs (G1 or G7) to calculate trajectory and account for any external factors that may effect bullet performance

bergerbullets.com

 

[Gila]

Thanks everyone for all of your great suggestions. I did use the Berger Calculator and it matches the AB engine in my rangefinder. I changed the same enviro variables in 4DOF and GEO and all four apps match almost exactly. At 571 yards, the center of the cone is the center of the bullseye, so increasing the MV from 2900 to 3000 is accurate. Looks like the difference is actually 100fps. I think the powder temperature and the speed increase of the barrel caused most of the MV increase. The rifle shoots great so I will take the dope charts and go hunting!
Berger range card:

 

[Wrench]

Take the dope charts and go shooting first.

 

[SDHNTR]

Thanks everyone for all of your great suggestions. I did use the Berger Calculator and it matches the AB engine in my rangefinder. I changed the same enviro variables in 4DOF and GEO and all four apps match almost exactly. At 571 yards, the center of the cone is the center of the bullseye, so increasing the MV from 2900 to 3000 is accurate. Looks like the difference is actually 100fps. I think the powder temperature and the speed increase of the barrel caused most of the MV increase. The rifle shoots great so I will take the dope charts and go hunting!
Berger range card:

View attachment 611985View attachment 611986

Glad you found an apparent solution. I’d be interested in seeing if a chrono verifies your findings.

 

[Gila]

It will be a few weeks before I can get back to the range…but yes I am curious what the chrono will show as well. Starting to scratch my head again though. The Hornady reloading manual version 12 shows the same G1-7 that the bullet box does. However their on-line app shows a different G1-7 for the same bullet (ELD-X). I wonder…

 

[Formidilosus]

It will be a few weeks before I can get back to the range…but yes I am curious what the chrono will show as well. Starting to scratch my head again though. The Hornady reloading manual version 12 shows the same G1-7 that the bullet box does. However their on-line app shows a different G1-7 for the same bullet (ELD-X). I wonder…

Look at the Mach number that is being used for the BC.

 

[SDHNTR]

It will be a few weeks before I can get back to the range…but yes I am curious what the chrono will show as well. Starting to scratch my head again though. The Hornady reloading manual version 12 shows the same G1-7 that the bullet box does. However their on-line app shows a different G1-7 for the same bullet (ELD-X). I wonder…

BC changes throughout the velocity range. It depends where on the curve they measured.

 

[Gila]

Look at the Mach number that is being used for the BC.

Bullet	Mach 2.25	Mach 2.0
7mm 150 gr. ELD-X	0.574 G1 0.289 G7	0.563 G1 0.283 G7
7mm 162 gr. ELD-X	0.631 G1 0.318 G7	0.626 G1 0.314 G7

I am using the .631 G1

 

[Formidilosus]

Bullet	Mach 2.25	Mach 2.0
7mm 150 gr. ELD-X	0.574 G1 0.289 G7	0.563 G1 0.283 G7
7mm 162 gr. ELD-X	0.631 G1 0.318 G7	0.626 G1 0.314 G7

I am using the .631 G1

At hunting ranges (900’ish yards), you’ll be fine with that.

 

[SDHNTR]

FWIW, Litz gives that 162 eldx average G1 at .626 and a G7 at .321.

 

[Gila]

Hornady (and others) are trying to move the industry away from G1-7 BC to LDC (Low Drag co-efficient) Hornady also states that most VLDs are measured on the curve at 2-300 yards. Hornady puts the focus at 800 yards with their ELDs. The 4DOF algorithm is really close to AB’s algorithm for this bullet. I am talking like about 1/4 inch drop difference at 571 yards. But the drop dope (data) doesn’t lie. If it is truly a MV of 3K, I should be getting very close to some kind of pressure signs? But I am not. I have been shooting that same action for over 20 years so I know that even the bolt lift is normal.

 

[SDHNTR]

Hornady (and others) are trying to move the industry away from G1-7 BC to LDC (Low Drag co-efficient) Hornady also states that most VLDs are measured on the curve at 2-300 yards. Hornady puts the focus at 800 yards with their ELDs. The 4DOF algorithm is really close to AB’s algorithm for this bullet. I am talking like about 1/4 inch drop difference at 571 yards. But the drop dope (data) doesn’t lie. If it is truly a MV of 3K, I should be getting very close to some kind of pressure signs? But I am not. I have been shooting that same action for over 20 years so I know that even the bolt lift is normal.

Did I miss it? What’s your cartridge and load?

 

[Gila]

Did I miss it? What’s your cartridge and load?

I guess i never did mention it….284 Win using new Lapua brass, WLR primers, H4350 53.7 gr, 162 gr ELD-X with a CBTO of 2.405 which is 15 back from jam.

*Just for the “newbies“. Every chamber and every barrel is unique and your CBTO will most likely be different. The max powder charge used will most likely be different as well. I do not suggest or condone in any way that you use this exact load in your own rifle.