Ballistic Drag Models in the ballistics calculator.

[mwkelso]

Heads up, I'm new to this. Thank you in advance for your patience.

I'm playing with drag models (G1 and G7) for a .300wm and am confused as to what they mean.
I'm using the Shooter app and am calculating for a Berger 190gr VLD Hunting bullet with a muzzle velocity of 2949fps. This is a made up velocity for the calculator.

My question comes to foot pounds of force specifically at the 1,000 yard mark. Using the different drag models they are nearly 1,000 ft/lbs different from each other.
Does a boat-tail bullet really have this much advantage? Or do the different drag models apply at different velocities?

G1 Model:

G7 Model:

 

[ShtrRdy]

There's something screwy with the G7 solution. There's no way a bullet going 2949 fps out of the muzzle can get to 1000 yards in 1.165 second. That is close to the time it would take in a vacuum. I suspect your BC number is not correct

 

[mwkelso]

There's something screwy with the G7 solution. There's no way a bullet going 2949 fps out of the muzzle can get to 1000 yards in 1.165 second. That is close to the time it would take in a vacuum. I suspect your BC number is not correct

Another point of uncertainty. In the calculator it is showing the BC the same for both drag models... 0.570

 

[ShtrRdy]

The G7 Ballistic Coefficient should be a smaller number than the G1 BC.

 

[mwkelso]

The G7 Ballistic Coefficient should be a smaller number than the G1 BC.

That's what I thought... I will check Berger and input the BC values directly from them, rather than relying on the app.

Going back to the top though, is a G7 more accurate to a boat-tail bullet's performance? Or does it depend on manufacturer, bullet, velocity, etc?

 

[ShtrRdy]

That's what I thought... I will check Berger and input the BC values directly from them, rather than relying on the app.

Going back to the top though, is a G7 more accurate to a boat-tail bullet's performance? Or does it depend on manufacturer, bullet, velocity, etc?

Yes, G7 drag curve more closely represents the modern low drag boat tail bullet design.
When you change between G1 and G7 in your Ballistic program you have to change the Ballistic Coefficent number AND tell the program that the number is G1 or G7.

 

[mwkelso]

I updated the BC's and drag models inside the app with the BC's directly from Berger's site.

G1 .566

G7 .290

Does this seem more realistic between the different BC's?
I made sure that G1 and G7 were specified in the calculator.

 

[ShtrRdy]

Much better. The time of flight is about 1.4 seconds. The bullet drop is within 3" of each other.