Do Not Mount Your Scope Level

[meatyrem]

That's a ball park estimation.

The true amount of spin drift at 1k will be based on the twist rate/bullet/velocity combination of one particular barrel. As with anything else it needs to be shot for confirmation.

So it gets you minute of deer then. Kinda what I was thinking.

 

[PNWdude67]

That's a ball park estimation.

The true amount of spin drift at 1k will be based on the twist rate/bullet/velocity combination of one particular barrel. As with anything else it needs to be shot for confirmation.

Yep, that's all you need. .2 mil at 1000 or .75 MOA half that at 500 and factor this in and be done with worrying about spin drift.

 

[Pro2A]

In a previous thread, a forum member stated he intentionally sighted in his scope to hit the target to the left of the 100yd bullseye to compensate for spin drift and Coriolis at longer ranges.

Question: what are your views about using a tall target to mount your scope with an intentional calibrated cant and not level?

Procedure: Draw 2 lines on a tall target, one line being straight up/down level like is normally done, then draw a 2nd line in a "V" shape to the left originating at the 100 yd zero. As the 2nd line is drawn upward from the 100 yd zero, it should get further and further away from the level line. The result being at the 1500 yd point on the target the "V" line would be maybe 3-10" to the left of the center/level line.

Now place the rifle level in a vise and zeroed/sighted-in at the tall target placed at 100 yds. Next, loosen the scope and cant it, keeping the rifle level, to align the scope reticle with the "V" line and not the level line. This would put an intentional ballistically calculated cant in the scope to compensate for your rifle's spin drift and Coriolis as you dial the scope upwards. Now during a hunting situation, you'd only have to compensate for wind holds and not worry about adding spin drift or Coriolis.

So, what are your opinions of putting an intentional cant in your scope while mounting it?

Why not sight in for cant, spin, Leprechaun farts??? Do you want to hit what you are intending to hit, or just fire for effect??? Is "close enough" your mantra??? Never comprehended intentionally introducing error into a precision pursuit. The Big Boys don't. They pursue the four cardinal pillars of shooting......knowledge, precision, repeatability, consistency. As with Bullet Drop Compensating turrets.......aka the lazy trigger yanker's solution.........introducing variations into the shooting process results in always off by at least "just that much." Cant of the rifle or rotation of the the scope....similar but different conditions......result in a less than precision adjustment for external ballistic parameters. Recall the effect of offset scopes on the M1 sniper rifles compared to today's precision rifles having scopes perfectly aligned with the bore vertical line.. Variables result in one always "chasing one's tail." Dial a firing solution, get another solution than intended....again, "off by just that much.". At close distances atmospheric and external ballistics, other than gravity, are negligible. That's why knowledgeable ballisticans and shooters zero at 100 yards to remove as many effects as possible. Obviously, that referenced member has a less than stellar grasp of external ballistic parameters, or isn't too keen on precision. As mentioned by others, Coriolis is dependent upon direction and origin (long/lat) of fire, unless one fires every shot in the same direction from he same origin, your Coriolis will always be a "NOT." Likewise with spin drift, not a constant over distances. And, then, there is external bullet jump (not to the lands). If one wants to be a shooter rather than a trigger yanker, one should learn the intricacies of ballistics and shooting and implement them toward Consistency, Repeatability, and Precision. That pursuit is what shooting is all about. The are no free lunches. In the end, only you can decide what is appropriate for you. But, first, to must define for yourself what is your pursuit. Just a really, really geezer's tries and trued mantra.

 

[PNWdude67]

So it gets you minute of deer then. Kinda what I was thinking.

If your zero is a shade (.5 MOA May be to generous a shade)left you really don't need to think about spin drift until lbeyond 800 on a deer vital zone sized target. A dead on zero is fine. If it's in between clicks? For me .05 mil, I cheat to the left. Then Just shoot for the wind and elevation. When the target is narrow 1 MOA or .3 mil wide and past 500 I start thinking about holding more left edge and taking that .1 out of a right to left wind correction.

 

[meatyrem]

If your zero is a shade (.5 MOA May be to generous a shade)left you really don't need to think about spin drift until lbeyond 800 on a deer vital zone sized target. A dead on zero is fine. If it's in between clicks? For me .05 mil, I cheat to the left. Then Just shoot for the wind and elevation. When the target is narrow 1 MOA or .3 mil wide and past 500 I start thinking about holding more left edge and taking that .1 out of a right to left wind correction.

That's helpful from you and huntnful. And also a 1/2MOA isn't that big of a difference up close either. Thanks.

 

[PNWdude67]

That's helpful from you and huntnful. And also a 1/2MOA isn't that big of a difference up close either. Thanks.

Nah it's not, most of us can't shoot 1/2 MOA in the field. And I agree 100 that 1/2 MOA left at zero is much better than 1/2 MOA right

 

[meatyrem]

So given say an 800yd max hunting range (won't shoot further at game than that) where is a good "zero" I was figuring 250-300yd is that a good zero to keep?

 

[HockeyDad]

In a previous thread, a forum member stated he intentionally sighted in his scope to hit the target to the left of the 100yd bullseye to compensate for spin drift and Coriolis at longer ranges.

It seems to me that if the Coriolis effect was significant, the only time a scope setting would be on would be when you were shooting in the same direction as you used to set the scope. Anytime you changed the direction of your shot it would jack up both windage and elevation.
And if you shot in a 180 degree different direction.......whoa Nellie !

 

[waveslayer]

Lol, good question. Don't dial for Spin see what the results are. I'm curious just for testing, report back and I'll comment further on the results. But that's bad advice, I'm still laughing

 

[PNWdude67]

It seems to me that if the Coriolis effect was significant, the only time a scope setting would be on would be when you were shooting in the same direction as you used to set the scope. Anytime you changed the direction of your shot it would jack up both windage and elevation.
And if you shot in a 180 degree different direction.......whoa Nellie !

Agreed, I have never factored in The Coriolis even when shooting out to a mile. The kestrel does if you have an azimuth data inputted. I turn off the data in the AB app for the phone. Spin drift adding to or taking away from a full value wind can make a difference beyond 1000 on large targets maybe 600 on small targets. I held just on the right edge of a small coyote facing me at 700 yards one time seeing a distinct right to left mirage figure it would certainly over come the .1-2 spin drift and move the bullet right… it was only a 3-5 mph tho and I just grazed the fur right where I held. A buddy of mine, best shooter I know keeps data on all the yotes he misses. He shoots at yotes a lot. 75% of the misses at long range are right. He's a phenomenal shooter!! So the tendency may be to not allow enough for the spin drift and combined wind effect. Still DO NOT cant your reticle to compensate for it

 

[Pro2A]

The point to take away is all else being equal set your turret 1/2 moa to the left to start when hunting. Then you have accounted for the bulk of spindrift to 1000 yards. If no wind set vertical and shoot. If wind use your reticle

Setting one's scope off merely means you "might" be correct at 1000yds, but you know you are off at 100yds, and have no real idea where you are between those two distances.............the lottery of shooting......spray 'n' pray.......a hand grenade approach. Shooters, as opposed to trigger yankers, demonstrate command of the four pillars of shooting......knowledge, consistency, repeatability, precision. "Good enough" is "good enough" for "good enough" applications, but it is still just "good enough." While a "good enough" solution implemented right now is better than a perfect solution next week in combat or hunting, I never build "good enough" into the foundation of any process because it will never be better than the elemental "good enough" foundation.

 

[TBell]

If I'm not mistaken, coriolis is dependent upon and sensitive to, the heading direction of the shot. I'll just let the Kestrel figure it out and dial.

Your correct, if he only ever shots due north that might help, but twice as far off shoting due south.

 

[7Rum Slayer]

I have for many years sighted my long range hunting rifles in at 1/2 moa left. It started back in the early 1990's when I used to pound long range rocks almost every weekend. I noticed all of my impacts on non windy days would hit the right edge of the rocks when yardages hit the 800 to 1000 yard range. Spin drift. At that time I had never heard of the coriolis effect. I just this year went back to a true center sight in as my Revic BR4 rangefinder compensates for spin drift and I did not want to distort that. I have also found that coriolis is very dependent on direction as well as time of flight, my ultra mags show way less effect than my creedmoor's as an example. To answer the OP, I would never purposely cant my rifle scopes ever, to many variables. Cheers and happy shooting. Jason

 

[Airedale56]

I think SnipersHide Lowlight has the EASY solution in his Spin-D drink.