Spin drift

marley

Very Active Member
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2,036
If spindrift accounts for an average of 1 MOA why are we not sighting our rifles in 1 MOA to the left?
 

buckhorn

Very Active Member
Messages
1,859
I learned about Spindrift from a long range shooter that knows more about it than I do. We sight in a half inch or so to the left at 100 yards. So at around 350 to 400 yds I start drifting a tad to the right at least with my set up.
7mm Rem mag shooting 180gr. Berger?s.
Actually my muzzleloader does the same thing at closer range of coarse.
FYI I use the Hornaday four dimensions of flight (4DOF) Ballistics calculator
 

mtmuley

Long Time Member
Messages
5,287
>If spindrift accounts for an average
>of 1 MOA why are
>we not sighting our rifles
>in 1 MOA to the
>left?


Because you will never in a million years need to adjust for it at sane ranges. mtmuley
 

littlebighorn

Long Time Member
Messages
4,131
LAST EDITED ON Aug-05-19 AT 09:18PM (MST)[p]LAST EDITED ON Aug-05-19 AT 09:17?PM (MST)

Marley,
Lately I have fudged my 100 yd. sight in a bit to the left to compensate for spin drift, but I typically don't plan to shoot beyond 700yds.

Here is a link to Gunwerks' solution to spin drift.
They sight in dead on at 500-700 yds, then you will be a bit left at closer shots and a bit right at 1000 instead of a full MOA.


Spin drift didn't help that elk you dumped at long range a few years back!!!
Poor boy was counting on a spin drift miss at that range! :D
 

marley

Very Active Member
Messages
2,036
Haha. I did have to adjust for spin drift for that bull. That spin drift accounted for 12 inches to the right at that range.
 

Millsworks

Active Member
Messages
416
If a guy is seeing hits to the right at less than 400yrds, it's likely you are a right hand shooter, it is recoil pushing your body.
Spin drift is real, but not a concern at 6-800 or less, and not much at the thousand.
Shooting a magnum a lot myself, I have learned to get my body more directly behind the recoil, as much as possible.
It affects people more if they are less than 180lb or so in body weight.
I have shared the range with many that claim to get drift to the right because of spin.
Placing the recoil pad more on your peck muscle, just at the shoulder crease helps me dramatically.
 

Millsworks

Active Member
Messages
416
I should add that a .30 Cal bullet would have at most around 4-5" actual spin drift at 5-600yrds, and maybe 8-9" at a thousand. High BC bullets would be less than lower BC would and smaller diameter bullets would be less also.
But, the various effects of wind would make determining "actual drift" impossible unless shooting indoors under climate controlled environment.
The wind and the guy behind the gun are the things to be concerned in real life hunting situations.
 

Cahunter805

Very Active Member
Messages
2,865
Spin drift is real. The formula is the following:
1.25(SG+1.2)tof1.83

Many of the better ballistic programs and solvers have spin drift feature and the windage solutions are usually calculated to include spin drift.
Spin drift is almost always a RH drift due to right hand rifling cut into barrels. Can?t recall ever seeing a LH cut barrel.
 

marley

Very Active Member
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2,036
I like the idea of zeroing at 600-700 yards so you are a little left at 100 and a little right at 1000.
 

Zeke

Long Time Member
Messages
9,218
>I like the idea of zeroing
>at 600-700 yards so
>you are a little left
>at 100 and a little
>right at 1000.

That's exactly what we do.
Our bench is actually set at 575 yards so that's close enough to shoot good groups and far enough to sight in for windage and this will compensate for most of the spin drift.

The caveat is if your ballistic program solves for spin drift and wind with the same solution. You might over-compensate if you rely on such a program.

Zeke
#livelikezac
 

Gator

Long Time Member
Messages
17,182
It's a real deal, BUT I think more guys miss judge the wind drift if it is combined with the spin. So if take 6" of spin and add in 3-5 mph wind even at 6-8 yds you could have a miss.

"I have found if you go the extra mile it's Never crowded".
>[Font][Font color = "green"]Life member of
>the MM green signature club.[font/]
 

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