Good evening Jon-K.
When I finish this, you will be sorry you asked
The level on a scope MUST be level and plumb to the spindle faces of the turrets - being level to the cross hairs is of little or no value, because the cross hairs can be quite a bit off.
Leupold says that they won't correct cross hairs unless they are 4 degrees off - that means that they let them out of the store with LARGER errors, and think that 4 degrees is acceptable.
,This applies to the standard scopes and "most" of the MK4 scopes. The MK4-M3 and the M3-LR are the exceptions, but at a street price of ~$1,400, they should be!!)
Here's the thing... When you are shooting at long range, you crank in the elevation, and set your rifle level with the bubble.
As you dial in the elevation, the center of the cross hairs,the "aiming point") moves down, which causes the barrel to be tilted up.
Now... if the spindle faces are not parallel to the bubble, the aiming point will also travel left or right, which moves the poi left or right.
So, as you crank in some ~40 moa, you can also be cranking in some ~4 degrees of "crab", which will cause your POI to drift left or right, and the error increases with range.
Most shooters don't realize that there is this built in error in the scope, and attribute the misses or group displacement to wind call errors, or to that mysterious "Spin drift",HA!!).
Setting up the scope for long range shooting is a real PITA.
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