Originally Posted By ziarifleman:
^^^ That's a really good post.

Essentially you're mounting your scope offset from the centerline of the bore.

Even 5 degrees adds .1 mil of wind, making left/right winds have different values.

Originally Posted By RePp:
You guys are so over thinking this. I shoot my 22-250 to over 700 yards all the time. Just zero it at 500 yards, hold dead nuts and just walk your rounds in tell you get a hit.

Originally Posted By Reorx:
/...The bottom line is that the greater the elevation correction you are dialling in, the more you want to avoid reticle cant.  This is why I think it is best to put a bubble lever on the scope tube not on the rifle, or the base, or the anything other than the scope tube...

Originally Posted By DakotaFAL:
One group will suggest setting up the rifle so that the optical center of the scope and reticle is directly over the bore, so that the vertical cross hair is in the same vertical plane as the center of the bore.  Those folks will advocate mounting the bubble level so that it is level to the rifle (regardless of whether the level is mounted on the scope base, on the rings or on the scope itself.

Originally Posted By DakotaFAL:


Well...that's one way to do it.

The downside is that the probability of a first round hit ends up being really low, and it's not exactly what I would call precision shooting.

Originally Posted By RePp:


First round hits are for suckers.

Originally Posted By DakotaFAL:


I found that when you stop accepting people's excuses, they start making hits.

Originally Posted By IMSHAKN:
In what way does that happen if the reticle is being held level? Please tell me how the scope can defy physics in that case if the reticle is level and the turrets are tracking? There is a reason top rifle shooters don't worry about making the reticle level with rifle.

We've been over this so many times on snipers hide where I spend my time online and go by a different user name. Plenty of experts in the precision world have debated this one many times with old school and newer shooters.

Originally Posted By Mister_H:
The center of the bore does not have a single fixed horizontal and vertical axis.

The bore is circular, whether the weapon is canted 15 degrees, 35 degrees, or completely upside down, the center of the bore does not change.

Originally Posted By urbankaos04:
Found this: Levelling your scope to the fall of gravity.

Originally Posted By wingsnthings:
Brick walls and roof lines are good sources of true to earth level lines but you need to be perpendicular to wall/roof line. If the rifle is supported in a level position then view a brick wall or roof line to check reticle level. I usually set receiver on a level and shim to get it level. 

Originally Posted By DakotaFAL:
I'm a little picky when it comes to leveling the scope.

1. I start by leveling the rifle.  This requires a level surface on the rifle.  The scope base can work, provided the receiver has been drilled and tapped so that the holes are on the centerline of the receiver. That's not always the case.    Sometimes a tang will work.  Sometimes you'll need to remove the rifle from the stock and use the bottom of the receiver, etc.

2. I then install the rings and check to see that the tops of the bottom halves of the rings are also level. If they are not, and the receiver is level, it tells me the receiver was not D&Td on center.  If the tops of the rings are level, I can put the rifle back in the stock and proceed from there.

3.  I then install the scope in the rings and adjust it fore and aft in the rings as needed to get optimum eye relief to accomodate prone, sitting and off hand positions.

4.  I level the cross hairs.  Some people use a level placed on the adjustment turret, and it's better than nothing.  However, the scope turret top however may not be completely parallel to the horizontal cross hair.  It works for ball parking the leveling of the scope but you need to use a plumb line to get it right.

You can use the edge of an interior wall except not all walls are as square as you'd think.  For example, I did some remodeling in the bathroom to remove the unused tub and replace with a large shower and removed the small shower and converted it to closet. I discovered that the top and bottom of the wall was 1/2" out of plumb, and had to order the mirrored closet doors cut accordingly.

The side of a building works better, on average, but you still have no guarantee of perfection.  You can also use a bubble level and draw a plumb line, but that introduces some variance based on how accurate the level is built and how skillful you are in interpolating the location of the centered bubble (it's how walls get 1/2" out of plumb in the first place).

Ideally you'll use a plumb line.  This is just a piece of string or mason line with a weight at the bottom, hung so that it can swing freely.   Gravity does the rest and gives you a line that is truly vertical.

Using a plumb line, and with the rifle level, I rotate the scope in the rings until the vertical cross hair is parallel to the plumb line. Then, I tighten the rings evenly, checking to ensure that the vertical cross hair remains parallel to the plumb line and the rifle remains level, while I snug and then torque the screws on the rings.

5.  I verify that the line of sight is located directly over the centerline of the bore by looking into a mirror with a plumb line in front of it. The vertical cross hair should pass precisely through reflection of the center of the muzzle and the center of the scope objective lens, while the rifle is level.

If you've got limited time and resources (no level, etc)  and/or a rifle action that is hard to level, this is the best shortcut method to getting a leveled rifle and scope.  You can hang a plumb line in front of the mirror and then use it to verify the crosshair is vertical when passing through the center of the muzzle and the center of the scope objective lens.  This also ensures the rifle is level, as what matters is the relationship of the line of sight to the centerline of the bore.  It's reliant on a calibrated eye ball, but properly and carefully done it will produce a very accurate result.  

Where this will not work is on a rifle with an offset scope, like the M1C and M1D Garand sniper rifles.

6.  On a high quality scope the cross hairs should be perpendicular to each other and the reticle should be square with the elevation and windage adjustments.  Determining they are perpendicular can be done visually before installing the scope as it is usually pretty obvious looking though the scope if the horizontal and vertical cross hairs are not at a 90 degree angle to one another.

However, you will need to do a box test at the range to verify that the reticle is aligned with the adjustments.

A box test involves zeroing the rifle and then starting in the lower left hand corner of a large piece of paper.   Place a target dot in the corner and shoot a 5 shot group to confirm the zero.  Then crank in the windage adjustment needed to traverse the point of impact to the lower right hand corner.   There are three things you are looking for:

a) Verification that the adjustment distance is correct.   For example, if I added 20 MOA of right windage, I want to see 20.9"  of movement in the center of the group on the target at 100 yards.
b) Verification that the scope is level, and that the windage adjustment is square to the reticle. A straight line drawn between the center of the first group and the second group should be level.
c) Verification that there is no hysteresis in the windage adjustment (usually caused by back lash in the adjustment screw.  The second group should be nice and round like the first.  If you see horizontal stringing with the first couple shots landing short of the group center, it suggests backlash, where it takes a couple shots for the newly adjusted reticle to come to rest against the same screw face.   For me, this is the kiss of death for a scope and it'll be sent in for repair, returned or sold as the situation dictates.  I have no use for a scope with back lash in the adjustments.

You then dial in the vertical adjustment as needed to reach the top right hand corner of the target and shoot a third group.  You're looking for the same three items as you were in the second group: correct distance for the elevation adjustment used (I use 30 MOA on a B-27 target - more is better and will magnify any errors present); verification of a level scope and alignment of reticle and adjustments as evidenced by the 3rd group being directly above the 2nd group; and no indications of back lash in the adjustment.

Then return the windage adjustment to zero and shoot a 4th group.  This should be directly over the first group, with no indications of back lash in that direction.

Finally, return the elevation adjustment to zero and shoot a final group.  This should overlay the first group, with no drift in POI, and no indications of back lash.

Once you've shot all five 5 shot groups, you should have a square or rectangle with 90 degree angles between all the sides  If the resulting square or rectangle tilts to one side or the other, it indicates the elevation and windage adjustments are not square to the reticle. In that case, you'll want to rotate the scope the same number of degrees to correct the tilt and repeat the test.

A couple degrees of difference is unfortunately pretty normal even on a high end scope but you are much better off leveling to the adjustments than to the reticle.   If you don't correct for this, all your elevation adjustments will result in a slight windage change, and vice versa.  This will mean the vertical cross hair is a couple degrees off vertical when the rifle is level, however, in the real world, the local horizon will often not be level anyway, so you're not really losing much.   If use a scope level on the upper rear ring, you can still verify the rifle is level on long shots more effectively anyway.

If you get a parallelogram where the angles are not 90 degrees, you've either got some cant in the rifle because you've improperly leveled the rifle ratline to the scope, or you've got internal scope adjustments that are not perpendicular to one another.   The former can be fixed but the latter cannot and will mean you are always going to get both a horizontal and vertical vector any time you make a windage or elevation adjustment.  That's another prime candidate for a return for repair, return or sale as the situation dictates.

Originally Posted By urbankaos04:

No rebuttal to this?