Spin drift

[dannyjbiggs]

Coriolis is from the earth spinning..... picture yourself standing on a big record player turntable and rolling a ball. Coriolis drives the bullet path to the RIGHT in the northern hemisphere. Always. But only 2-3 inches at 1000yds (and actually, it's the earth moving out from under...)

"spin drift" is actually a drag function. A bullet is dragged by it's tail. Basically wherever the tail points it is driven that way by deceleration. So when a bullet points it's nose INTO the wind (this is what a bullet does, regardless what Boatwright sez) it's tail is pointed down-wind so it's dragged downwind. And due to something called "yaw of repose" it's not point EXACTLY into the felt wind, it's got some lag. This slight lag orients the butt of the bullet just slightly "right" of the felt wind. In the case of wind on a bullet, "right" is UP in a right/left wind and DOWN in a wind from left to right so bullets blown to the left hit high and bullets blown to the right hit low. (Again, these are FACTS not Boatwright's opinions. Real scientists took pixtures even, to "prove" the math....)

A forward moving but falling bullet has a wind on it's belly.

The wind on it's belly means it's dragged to the RIGHT 8"-10" at 1K

Now, can we SEE IT?? Dunno.... II don't know if I can.

Between the two I figger 4" right at 600 and 12" right at 1000 but I can't really observe it.

I shoot in my own yard.

About 15yrs ago we were shooting 1000yds on an absolutely perfect evening. We could spot "wishes" in the air for a half mile and the whole air mass was nearly static. We THOUGHT, we BELIEVED that that day we actually observed "spin drift" but today, having spent 25yrs trying to even find a "dead-air zero" with limited success........ I no longer believe we saw it.

Others' experience will differ but that's been mine.

Good write up. Many years ago when I shot Palma rifle, I "observed" spin drift; but, I did not recognize it for what it was, or as we commonly discuss today?! As with everything, I would zero and index my Warner #2 sight at 200 yards "windage zero". Later, when I found myself shooting thru the Palma Match Course, I was befuddled when that windage zero was not accurate! I even bemoaned my Warner sight for having a mechanical windage error. After shooting a Palma match, I'd come home, go to the range and recheck my "new" newly indexed windage zero at 200 yards...and it would be off from where I had re-indexed at long range? I went through this cycle more times back then than I care to recount. I asked other Palma shooters if they were having a similar "mechanical" problem with their Warner sight. My friend, Jerry Tierney, finally told me it was a "spin drift" issue.

Now that I shoot F-Open, I still "wind zero" my rifle scope at 200 yards, which is generally good thru the Mid Range Course, except for 600 yards. At 600 yards, I start to apply a "spin drift" adjustment, and another adjustment at 800 yards, and so on, different adjustments for 900 and for 1000 yards. Spin drift is real.

Dan

 

[Depart123]

now you can't delete it once you sober up

 

[Delfuego]

So you bust into a thread...stomping dicks....and I'm the asshole?

When can we expect your peer reviewed papers on this matter?

now you can't delete it once you sober up

Will you guys just kiss already.

 

[hockeyref]

Good write up. Many years ago when I shot Palma rifle, I "observed" spin drift; but, I did not recognize it for what it was, or as we commonly discuss today?! As with everything, I would zero and index my Warner #2 sight at 200 yards "windage zero". Later, when I found myself shooting thru the Palma Match Course, I was befuddled when that windage zero was not accurate! I even bemoaned my Warner sight for having a mechanical windage error. After shooting a Palma match, I'd come home, go to the range and recheck my "new" newly indexed windage zero at 200 yards...and it would be off from where I had re-indexed at long range? I went through this cycle more times back then than I care to recount. I asked other Palma shooters if they were having a similar "mechanical" problem with their Warner sight. My friend, Jerry Tierney, finally told me it was a "spin drift" issue.

Now that I shoot F-Open, I still "wind zero" my rifle scope at 200 yards, which is generally good thru the Mid Range Course, except for 600 yards. At 600 yards, I start to apply a "spin drift" adjustment, and another adjustment at 800 yards, and so on, different adjustments for 900 and for 1000 yards. Spin drift is real.

Dan

I can remember a discussion in the pits about Spin Drift maybe 15 years ago when an old Palma shooter said, "Get you no wind zero at 100 yards, add a minute and call it good."

 

[Gene Beggs]

Wow Al, you've come a long way boy!
I'm impressed
Good for you and hang in there.

Gene Beggs