Smyth Busters: Is It Important To Level Your Scope?

‪@CalebSavant‬ recently discovered a spate of videos on the Interwebs that claim it doesn't matter if your scope is crooked when you mount it on your rifle. Do people actually believe this? After losing a few nights' sleep over this trend, Caleb has enlisted his fellow Smyth Buster Steve to tackle the matter head on. Normally, a scope is mounted with its center axis aligned with the rifle's the bore and the crosshairs level relative to the gun itself. Advocates of the "Crooked is OK" school of thought say you should shoulder your rifle and then adjust the crosshairs to make them level based on how you hold the gun.
When you aim, you will have to tilt the rifle to get the crosshairs level with the horizon. As a result, the rifle will be canted, and due to "mechanical offset," the scope will not be aligned directly over the bore. The point-of-aim and the bore centerline are not parallel. They actually cross each other at some point and then diverge. The scope will be accurate at that point where those invisible lines intersect. But at other ranges, it is not. You can use the scope's windage and elevation adjustments to compensate for some of this, but no scope has adjustment knobs for DIAGONAL adjustment!
Example: Your rifle has a properly aligned scope zeroed at 100 yards. If you want to hit a target 300 yards away, you just have to aim higher. With the Crooked Method, you have to aim higher AND off to the left or the right, depending on which way you're canting the gun, to compensate for an imaginary "windage."
The effects of the Crooked Method get worse the farther away the target is. The longer the range, the more the bore and line-of-sight diverge, and your target groups will open way up. If you're shooting an AR-15, it's even worse. The higher mechanical offset of the typical AR-15 scope mount means a crooked scope will be even more dramatically inaccurate at long range! If you're shooting rapid fire at close targets, a canted scope probably won't make a noticeable difference in your rifle's accuracy.
So this myth is thoroughly BUSTED. Don't let the way you hold your rifle determine how you mount your optic. Mount the optic correctly, and teach yourself how to hold the rifle correctly! There's a reason why folks who shoot at small targets at long-ranges have their scopes perfectly leveled out, often with the aid of a bubble level.