Scope level to ground or target?

[shockman]

Yes indeed and warm enough here to go shoot some more.

If sighting in, with spotter and unlimited rounds I'd say "level" is a preference call. If your set-up isn't at the same conditions as when you verified your scope install (shoot the box, do a vertical scope test, was your rifle level then?) then the drawbacks of a canted setup are that a single windage adjust affects vertical as well; vise versa for the vertical adjustment on a canted rifle. If you're a scope adjuster mid-match instead of a hold-over'er then those mid-match adjustments can really bite you.

Sight in, and maintain rifle in that position works great for many; move to another competition / range / bay / universal railed mount / truck / gun case / shooter / etc... and all bets are off.
My preference is to bubble level the rifle on sight rail (and bags where i can) and on scope install align the scope with a tall target test IE make sure a vertical adjustment is as much vertical only as i can. Then at a match, it's set up rifle to bubble level

Now, if only i can get that windage knob to stop shifting the wind every time I reach for it.

-Mac

What he said!
I think you guys talking circles are missing the point of scope level. If you are only holding off then the circle theory applies but spin 5moa on scope dial and hold center and you may find you have lost your elevation.
Marc

 

[CharlieNC]

A simple example rotate the target to 45deg, level the scope reticle with the line, and see where you hit. Answer, not where you're aiming. Exaggerated example, but just a more extreme degree of the same effect.

 

[D-4297]

A simple example rotate the target to 45deg, level the scope reticle with the line, and see where you hit. Answer, not where you're aiming. Exaggerated example, but just a more extreme degree of the same effect.

Agreed . You are adding cant to the rifle by doing so , and changing the parallel axis lines between the scope the rifle and target . Put 3-5 degrees cant on your sighting , and I'll make a pretty safe wager your POI is going to be in the 4 o'clock direction off center . I got careless with having my rifle level , and collected I few nines for it .

 

[Mr. Ten-X]

Technically, the vertical crosshair should be set up plumb to follow the rise/fall of the projectile. Then, the level is adjusted square to the vertical crosshair. Looking at a plumbed line on a target is a good means of adjusting the reticle rotation.

 

[JMayo]

If rifle is cantered bullet won't fly right.

 

[Fairchaser]

If rifle is cantered bullet won't fly right.

Could you elaborate on this. I’d like to understand this a little better. Thanks

 

[Joe Salt]

Mr.Ten-X has it right if your bench or ground your on is level, then level the gun, the scope and put a plumbed line on the target real easy.

Joe Salt

 

[kzin]

Could you elaborate on this. I’d like to understand this a little better. Thanks

A no wind zero actually aims the bore somewhere on a vertical line above the target center.
Gravity pulls the bullet down in flight and it hits the x.

Say it's 2 feet above.
Cant the rifle 90 degrees right.
Now your bore is pointing 2 feet right and not at all above the target.
Bullet impacts 2 feet right and 2 feet low.
Lesser cant requires some trigonometry to calculate the error.

 

[jelenko]

I think 'doesn't fly right' means 'doesn't fly where you might expect'. The bullet will land to the side the cant is leaning and down a bit from the POI without a cant.

 

[JMayo]

Amazing what the holographic sight does on my AR when i tilt the rifle.

 

[sdean]

I think 'doesn't fly right' means 'doesn't fly where you might expect'. The bullet will land to the side the cant is leaning and down a bit from the POI without a cant.

There you go. There is a reason to have a level on your scope.