Applying spin drift to scope settings

[Sinclair]

A search didn't reveal anything on this subject so here goes. For my cell phone, I have just acquired a new ballistic program that list the spin drift data separately from elevation and windage. O.K. so how/when do I apply the spin drift correction to my "normal" scope settings? My rifle has right hand 1/8" twist and is a CZ 527 Varmint in 6.5 Grendel.

[tdbru]

go read hornady's user manual for the 4DOF on their web site. that'll give you a feel for spin drift. basically for RHT the bullet will drift to the right.

if your ballistic app doesn't add spin drift into the settings automatically, then see what the number for spin drift is in MOA or MIL (depending upon your scope click values) and then move the scope left that amount.

this will not make much difference until you get out LONG. and just to mess with you, a R-L wind will cause the bullet to rise, a L-R wind will cause the bullet to drop, both relative to no wind zero.

i can't shoot well enough to be able to see these fine effects. they are lost in my normal dispersion.

-tdbru

[Dug Silverman]

[LRRPF52]

Spin drift is something that you would account for in hopes of a first-round hit, when testing your ability to make first-round hits.

Like humidity, it has very little impact on windage deflection within a certain range.

With the calculators that account for it, you can run the program with your load and see exactly what that difference is.

You might see .1 mils of deviation in favor of RH twist at 700yds, and .2 mils at 900yds.

I personally prefer to hold for wind, not dial it in.

The amount of shifting I constantly make in the wind is too fast to dial anyway, and spin drift is imperceptible to the shooter in that type of LR shooting.

[A5BLASTER]

When I shot for paper groups at 900 yards with my 123 eld-m loads for my cz varmint grendel, my sterlok app gave both with and without spin drift.

I couldn't see any difference in impact between the 2 calls sterlok gave me.

I'm for sure not the best shot but I still couldn't tell the diffrence.

[Sinclair]

Thanks guys, I thought as much that I probably could not see any difference, but my inquisitiveness required me to check with the experts just to hear what you guys had to say. I currently have no place to shoot more than 300 yds; however, I wanted to know what affect it had to say 600 yds.

[LRRPF52]

[bamban]

About half minute at 1K for spin drift. I have been burned a couple of times when we used to shoot M1A at 1K for not thinking about spin drift on wind change coming from the left.

[Lemonaid]

A bit off topic but an interesting vid about Coriolis effect. Much controversy in the comments section. https://www.youtube.com/watch?v=jX7dcl_ERNs

[Klem]

I've wondered about this myself. Spindrift is a constant and with all the wind to worry about I haven't noticed it. My calculators tell me to crank on at least 0.1-0.3M with no wind.

I regularly shoot 400M (437yds) which is supposed to be 0.1M spindrift. Sometimes I compensate and sometimes I don't and it doesn't seem to make any difference. Seems wind is always there subordinating and confounding it.

[centerfire]

Spin drift is something that you would account for in hopes of a first-round hit, when testing your ability to make first-round hits.

Like humidity, it has very little impact on windage deflection within a certain range.

With the calculators that account for it, you can run the program with your load and see exactly what that difference is.

You might see .1 mils of deviation in favor of RH twist at 700yds, and .2 mils at 900yds.

I personally prefer to hold for wind, not dial it in.

The amount of shifting I constantly make in the wind is too fast to dial anyway, and spin drift is imperceptible to the shooter in that type of LR shooting.

Yep. Even at 1500 yards wind is a much greater influence than spindrift.

[centerfire]

It is kind of interesting, inside of 500 yards the hits are pretty much gimme's assuming you don't totally screw up the dialing. "High Angle" stops being all that high angle the further you get and the closer in you are the less influence the angle has. Under 20 degrees at 1K yards is only .2 or .3 mils depending on the cartridge. 15 degrees is a fairly high angle over 1K which still only means .2mil less dope or less.

Point being, verifying your dope and calling your wind correctly is by far more important to small rifle cartridges than worrying about tiny computer calculations that really only relate ELR or artillery.

[LRRPF52]

I was talking about rifle cant left and right having an influence on trajectory and wind past 600yds, vs slope angle shooting uphill or downhill.