Do Not Mount Your Scope Level

[JustMe2]

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?

 

[quigley257]

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.

 

[LRNut]

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 offset for spin? Personally, I zero at 500 under perfectly calm conditions then enter what the offset would be at 200 in my SIG that results in no spin at 500.

Your solution is overly complicated. A can't will also result in very small changes in vertical impact at long range as well.

Another issue your solution doesn't address is aerodynamic jump, which is real at extended ranges. A rangefinder that accounts for spin, coriolis, and aerojump solves all three issues.

 

[JustMe2]

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.

Yes, but my understanding is Coriolis is negligible at normal hunting distances and is only significant at extremely long distances like 2 miles, etc. The more significant error comes from spin drift. I've never calculated just the Coriolis error from 500 to 1500 yds.

 

[Huntnful]

I was that poster that sights in slightly left. Don't cant your scope to account for it. That will effect your vertical adjustment and really can't be done precisely. I would not recommend that in the slightest aspect. Just mount it level and center it up at 700 yards, or sight in a little left. Much more simple. Of course the further out you shoot, you really need to take it into account. But within 800 yards, just 1/2 MOA Left at 100 yards will have you covered.

 

[Orange Dust]

Doesn't Tubb have a retical that does that?

 

[Beluebow]

 

[Coyote Shadow Tracker]

When talking about the rotation of the earth and then ballistics used for long range shooting you really should get a good device like a Kestrel with a Ballistic Program installed. You have to be a very good mathematician to figure it out. You should have the Longitude/latitude/altitude/ direction you are shooting (360 degrees) after you get that then you can figure in bullet spin drift right/left, temp, humidity, BC, Velocity. This is sight specific so if you are trying to do something with your scope at one area, it will not be the same in another area.
Unless you are shooting ELR and past 1K don't worry about it. If you are going ELR just get yourself a Ballistic Program with a Kestrel.
Sight your rifle in at 100 yards and let the computer do the rest.

 

[six pack]

Seriously? At 100 yards? All things considered, I would guess that would not be likely to result in the desired results. Sounds WAY TOO complicated for my simple mind. I should probably stick with 'Kentucky windage' and my Kestrel. Good luck and let's us know how that works out.

 

[Willys]

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

 

[TxHeartShot]

100 yds? Why would you need a scope at 100 yds? Just huck a bullet in their boiler room and get your skinnin' knife out.

 

[meatyrem]

I was that poster that sights in slightly left. Don't cant your scope to account for it. That will effect your vertical adjustment and really can't be done precisely. I would not recommend that in the slightest aspect. Just mount it level and center it up at 700 yards, or sight in a little left. Much more simple. Of course the further out you shoot, you really need to take it into account. But within 800 yards, just 1/2 MOA Left at 100 yards will have you covered.

Are you then saying at say 600 or 800 you'll hit spot on? So the spin only moves that 1/2 moa from 100 to 800?

 

[Beluebow]

Are you then saying at say 600 or 800 you'll hit spot on? So the spin only moves that 1/2 moa from 100 to 800?

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.

 

[PNWdude67]

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?

Had to check date on post to make sure it was not 4/1. Ok so we are asking a serous question. answer:
No, and here's why. First of all "spin drift" is no more than .2 mil or 7" at 1000 yards. It's enough to be aware of yes, but not to attempt the compensation trick you are suggesting.it's iStill sub MOA. Having a 100 yard zero .1 mil left of center actually makes way more sense. If my zero is .05 mil right I click it left to be .05 mil left. If it is dead on I leave it alone. Now, what's your windage reference doing when you cant your vertical?? You're canting your right to left wind hold or dial to be low and the left to right wind hold to be high! So now you have to factor in a jacked up or down elevation variable which is already affected by wind jump, right to left will result in a high impact and left to right low and your reticle is now biased and your mind blows up when you can't hit a **** thing all day long. Also, which depending on the wind value can be much more significant than the constant variable of spin drift.

KISS, use a ballistic calculator… I like AB. Learn to read wind direction and value. Know your gun number or speed. If you don't want to figure it out use a 7 mph gun for 2800 fps an 8 for 2900 and a 9 for 3000 with high BC bullets. What does this mean? For your 7mph gun when you have a 7mph wind,God so created the world to give us a physics cheat sheet. At any yardage 100-1000 yards your wind correction in .10 mils will be equal to the yardage. 400 hold .4 500 hold .5 600 hold .6 and so on. With a higher gun number or mph gun the wind value needs to match the gun number. So to compensate for spin drift at 1000 yd factor in the .2 right and hold less or more wind. If you have an MOA scope?? God did not love you as much as the milradian shooter.
MOUNT YOUR SCOPE PLUMB to your rifle systems level reference. Zero at 100 then input and get good data from a ballistics calculator. Lastly, shoot a lot while keeping your face in the gun to see what's happening down range and get better at making first round impacts.