spin drift

[chad44]

How many of you account for spin drift? I was shooting to validate my trajectory on the G7 ballistic program and had not been accounting for it but noticed it gets pretty significant past 700 yards. Do I add that value on top of my wind? I have it in a separate column. wind call for 10 mph 3 oclock is -4.2R moa and spin drift is -5.7R moa. so would I dial in 9.9 left?? that just seems huge to me but that is what I get.
I'm shooting 7mm rem mag at 2949 fps with 168 gr berger hunting vld with a 1:9.5 right hand twist.
thanks

 

[Broz]

No, you spin drift alone should be 1/2 to 3/4 moa right at 1000 yards . Either add it to or subtract it from your wind correction depending on if you have a right or left wind.

Jeff

 

[chad44]

Ok. I'm just confused as to why the g7 program has it as such a high value????

 

[scsims]

Maybe the software is giving you the value to use for just wind, or you can use the spin drift value with the wind part of that value.

Cornilious effect and spin drift are automatically calculated into my windage MOA program if you indicate it to do so.

 

[BlackStreak]

I just checked my #'s and as Broz said the spin drift is right at 1/2 moa at 1000 for two different rifles. One is a 1:8 twist and the other is 1:11.