Need a little technical help

loosesniper2000 · #1 10-10-2010, 07:19 PM

Here's the scoop. I shoot every week past 1000 yards but lately I'm having a little trouble getting things figured out. Here's the situation I'm having.
I use the Nightforce software and put in the correct info concerning pressure, temp, altitude, scope height humidity and so on. My velocities were checked using 2 different chronographs (ced and pact) everything is entered right but when I shot at 1200 yards tonight my shot is consistantly 2 moa off. (high) This is happening every week and no matter how many times I double check things it's always off.
If you know a solution I'm all for it. I am using several different guns and get the same consistencies.
Thanks for any help, Dustin

loosesniper2000 · #2 10-11-2010, 05:11 PM

Any suggestions?

partisan1911 · #3 10-11-2010, 05:19 PM

Has it alway been 2moa off at that range? Maybe the bc isn't being calculated correctly in the ballistics program? Or even a lot change in your bullets?

Oliveralan · #4 10-11-2010, 07:15 PM

are you adjusting for the magnus effect? are you also high at different yardages or only 1200? or is it less at shorter yardages?

loosesniper2000 · #5 10-11-2010, 08:32 PM

I adjusted for spin drift but the magnus effect I don't believe is on the software. If it is please let me know. As for the distance it's at other ranges as well. I would say it starts to differentiate about 800 yds.
It's really bugging me I can't figure this thing out. I'll try another chronograph but I doubt that will help. I actually experimented with changing the B.C and it works out perfect. I know there's got to be something I'm missing. I know the magnus effect is a force perpendicular to the line of motion, but that usually equates to a horizontal drift.
I appreciate the feedback, but still let me know where the option is to check this.
Thanks

loosesniper2000 · #6 10-11-2010, 09:02 PM

Quote:

Originally Posted by partisan1911

Has it alway been 2moa off at that range? Maybe the bc isn't being calculated correctly in the ballistics program? Or even a lot change in your bullets?

I'm using the JLK 7mm vld bullets in one of my STW's They said the bc was .690 and I'm shooting at 1460 altitude. I really don't know how to tell if the bc is calculated correctly.
I'd be fine if it was one bullet but I'm also experiencing it with 3 other guns

Oliveralan · #7 10-11-2010, 09:21 PM

Magnus affect is about 15% of your windage. A right hand wind (assuming right hand twist bbl) means your bullet will impact high by around 15% of your windage (exact percentage varies with twist rate, muzzle velocity and a lot of others but 15% should get you very, very close).

If you have a predominant right hand wind, that would explain why you shots are. However 2mins is a lot, you would have to have dialed a LOT of windage

also, what is the terrain like? You could very well be shooting through an upwards wind. That would raise impact.