Different Gun Number (MPH) Right to Left vs Left to Right

[Sheriff_Will_Teasle]

Hey all - I'm double checking DOPE prior to a match at Pawnee in NE Colorado this weekend. My solver and my data both agree that my gun (24" MRAD in 6.5 CM / 140 gr ELD-M @ 2800 FPS) is a 5 MPH gun when the wind is blowing Left to Right and an 8 MPH gun when the wind is blowing Right to Left. Another way of looking at my data is that my spin drift is equal to a 1.5 MPH wind from left to right.

Does anybody use the different gun numbers? At 1000 yards with a 9 o'clock wind of 5 MPH, my hold is 1 mil left. But from 3 o'clock with a 5 MPH wind, my hold is only .6 to .7 mils right. Enough of a difference to cause a miss if not accounted for properly. Likewise, at zero wind and 1000 yards I have to hold .2 to .3 mil left.

I haven't seen this mentioned anywhere else - any thoughts?

 

[6.5SH]

Turn spin drift and aerodynamic jump off in your solver and check again.

ETA:
The humorous answer here:

 

[st1650]

Spin drift.

 

[KnowNothing256]

Also, if I have the environmentals right (I used Briggsdale), you have a 7 MPH gun, and if you want to use the gun number at long ranges, you'll need to bump it a tenth at 700 yds and another extra tenth at 900 yds. Have fun out there.

 

[st1650]

140 ELD-M out of a 24in tube usually isn’t a 7mph gun unless you’re shooting quite high and in hot weather. It’s more of a 6.5 mph depending on environmental.

Even my 147 eld-m out of a 26in tube is barely 7mph.

 

[KnowNothing256]

140 ELD-M out of a 24in tube usually isn’t a 7mph gun unless you’re shooting quite high and in hot weather. It’s more of a 6.5 mph depending on environmental.

Even my 147 eld-m out of a 26in tube is barely 7mph.

Did you happen to read where OP is shooting? At like 5300' elevation? And in the 80's this weekend?

 

[jrsandiego12]

Yeah, I've seen this. I always calc my wind mph number with 0 wind, and turn spin drift off, then mentally account for sprin drift by adding or subtracting it from the hold depending on wind direction.