How do you get your scope level on your precision rifle?

[chopper 1]

You forgot -

If the scope is always held plumb, a little rotation of the scope in the rings will matter little.

For instance, if the bore is 1/4 inch to the left of plumb when the scope is plumb, and then the gun is zeroed at 200 yards, the bullet will continue to go right until it is 1/4 inch to the right of the bull - at 400 yards. ( Bulls eye - not Bull moose)

If the scope is adjusted then to shoot 12 inches higher at 200 yards but still held plumb, the bullet will still be on the plumb from bull at 200, and at 400 will have dropped straight down the target and will again be 1/4 inch to the right.

If however, the rifle is held off-plumb from how it was zeroed, any rise that was adjusted in to compensate for bullet drop would double the offset of bullet line-of-fall to the bull plumb line from 200 to 400 yards - and it would be considerable.

Remember how the bullet may rise to the height of the scope in say twenty-five yards, well if the scope is held out of plumb by 1/4 inch from the bore, then it will keep going in that direction by 1/4 inch for every 25 yards.

So at 25 it will still be zeroed - or very close, and at 200 it will be 1 3/4 out and at 400 it will be ( 15 x 1/4 = 3 3/4) 3 3/4 inches out in the direction that the scope was leaned. Lean it one way once and the other way once and we have quite a spread.

In application of this for hunters Leeper and RifleDude are right. Put on your hunting clothes and grab your gun and sight out the window at the cat down in the pasture - then check the crosshairs to the window frame - then fix 'em till they come up plumb.

The trouble is carrying the window frame around the bush to line up with. : )

In application for benchrest - use a built in level or a bench block that levels the rifle consistently - because if you get the crosshairs off plumb, that will stack up by the total distance to target, divided by the distance until the bullet first crosses the line of sight ( less one ) times the amount that the crosshairs are out of plumb from the rifle bore. 1/8th of an inch out one way and then the other might spread your 1000 yard group by as much as (1000 divided by our assumed 25 yards to the first time the bullet crosses the line of sight = 40 - 1 = 39 X 1/8 = 4.875" x 2 ( because you leaned first one way then the other) = 9.75 inches of spread at 1000 yards.

If held plumb and zeroed, even a poorly leveled scope is better than a perfectly mounted scope held even a little off plumb.

You forgot about wind -
A miniscule cant variation will be a major deflection at long distance.

AND - shouldering a rifle - always 1/4 inch off each time ?

No way -
If so - if you try to keep vertical it will always be plumb each time -

No way -

 

[coyne_5]

If I can't use feeler gauges between the bottom of the scope and the rail, then I simply set a mirror up far enough away that it comes in clear when looking through the scope. Set the gun on a bipod or gun vise and look through the scope. When the vertical crosshair bisects the muzzle I tighten the rings down the rest of the way, works like a charm.

 

[Leeper]

Farlsincharge,
Though no longer young, I am still capable of grasping simple geometry. If you are adjusting, your turrets need to be level. If you are holding over (or using a dot array), you reticle has to be level. It is preferable that the two co-incide. If you level you turrets and your crosshairs do not co-incide with them, you will have a heck of a time holding level in the field. If you level the reticle and the turrets are not level, the scope will indeed track off to one side. Happily, most scopes have a windage adjustment so one can compensate for this. Of course, the option is to get another scope on which the turrets and reticle are true. I'll tell you what, if I paid over a thousand dollars for a scope, the reticle and turret would be perfectly aligned or I wouldn't take it out of the store. Regards, Bill

 

[kombayotch]

There are many tricks for getting a scope leveled when installing it, but in the end you should take the rifle to the range, put up a big piece of cardboard with a leveled vertical line on, and an aiming point at the bottom. Zero the rifle and then shoot one group at the aim point, then crank the turret up to the highest elevation you plan to use (plus a bit) and fire a second group at the aim point. The second group should be up higher, but right on the line.

There is no fool proof method for installing a scope level... things need to be tested for confirmation. The astute long range shooter will also run a box test and verify that the turrets are tracking accurately.