AB Mobile Anomaly... Maybe?

[mao0720]

So I am getting ready to work up a load for the 185gr Berger Juggernaut in my F/TR rifle. Specs are Nesika model K action, 30" Heavy palma 1-10 twist barrel 308 win 2012 fullbore reamer .050 freebore (I know .050 is short for the 185s, but lets not get into that here). I have been shooting the Berger 155.5gr fullbore at right at 3000 FPS for the past year. I wanted to run the theoretical numbers through AB mobile before I started load development with the new bullets, just to see what advantage I might expect to see over the 155.5 fullbore. So I input a new round in AB for a 308 win with 185gr Juggernaut going 2750 fps, which gave me close to the same Muzzle Energy as my 155.5gr load going 3000 fps. I then ran a trajectory chart for both loads with a 2 mph, 3 O' Clock wind. What I got was something I did not expect at all. AB gave me a 1.5 MOA drift for the 185gr Jugg., and a 0.9 MOA drift for the 155.5gr Fullbore, both at 1000yds. I don't believe this to be accurate, but Im not sure how to get accurate information from this. If anyone can help please point me in the right direction.

 

[DocUSMCRetired]

Just to cover some basics before we start breaking it down.

Did you use a Custom Drag Curve?
Did you verify the bullet lengths? - This is a big one for spin drift.

 

[mao0720]

No and no. I used the standard pre loaded bullets in the bullet library.

 

[DocUSMCRetired]

I need you to double check your bullet lengths, make sure they are correct and not blank.

 

[mao0720]

The bullet length was blank for the 185gr Juggernaut. I just measured a small batch of both bullets and got 1.35" for the Juggs and 1.20" for the 155.5gr FB. When I input those numbers I get .8 MOA drift at 1000yds for the Jugg in a 2mph full value wind, and a .9 MOA drift at 1000 for the 155.5 FB for the same wind. That isn't quite as dramatic of an advantage as I was expecting, but its a step in the right direction. Any other tips to get a more accurate trajectory?

 

[Quickoz]

Try using 10MPH full value wind to see difference.

 

[Jay Christopherson]

Try using 10MPH full value wind to see difference.

^this. 2mph doesn't show you much.

 

[mao0720]

Shows you the difference if you miss a light let off or pick up of the wind. That's why I was using a 2mph wind. Yes using a 10mph input value will show you a bigger difference but a 10 mph wind change is pretty easy to read and make the decision to stop shooting and wait for a condition to return. But a 2mph wind change is subtle and that is where you lose points. I see what you guys are saying though, for the sake of computations using a stronger wind value will show the difference between the two bullets more clearly.