Some pretty good apps are out there to check and see if surfaces are truly horizontal.

Anyone else toyed with them to check the crosshairs in rifle scopes. They all seem to work very well IMO. I just lay my iPhone on the top screw cap of any scope that’s mounted on a rifle and peek through the scope to check the crosshairs. Seems close enough for government work.

How does that tell you if it's square to the rifle?

This is the ticket IMO. Simple, and gets the reticle aligned true to action/bore.

RETICLE-TRU ALIGNMENT DEVICE

https://parabola-llc.com/

Good point.

Given there isn’t much that can be easily done with scope bases and rings, or to change the orientation of the crosshairs in the scope, isn’t the average rifle owner left with aligning the final setup to truly horizontal?

Not sure what surface on the average rifle could be referenced to determine it being true horizontal. A plumb line on the butt plate of the stock perhaps? Somewhere it would seem an assumption must made as to what reference benchmark must be chosen on the rifle itself as a starting point.

Granted, the discussion has quickly gone from “toying” with smartphone apps to getting down to the gnat’s bristle on how best to identify the x-axis of a barrel so that you can verify it is true horizontal.

On a Savage you can pull the bolt and put the level on the bolt races that extend rearward out to the action in front of the safety. Sometimes you have to remove the action from the stock, if its too tall at that spot the stock can interfere. This may work sure on other actions, or not.

So now we’re back at the factory making the assumption those races are true to the X axis of the barrel.

Not challenging you at all my friend but only saying where is that first assumption made and at what point, if ever, can we say it’s safe to just “eyeball” it.

The fact is, whatever measurement tool or device you use, there must be a starting reference point on the rifle itself that indicates a clear assumption (if there is such a thing) the X axis of the barrel is true horizontal.

I use this, but it only works well on bolt actions with decent-sized bolt rails.
Wheeler Scope Level

It works fairly well, but it’s no help on single shot or “modern sporting rifles”.

No offense but those cheap bubble levels aren't the most accurate things in the world. It'll get you close though, probably.

A plum line works awfully well. Also I always setup to level to the shooter not the rifle.

This is the most sensitive bubble level app that I’ve come across. It detects the slightest movement of the phone well beyond what can be seen with a traditional bubble level.

https://itunes.apple.com/us/app/level-tool/id618064263?mt=8

It does get close, as long as the gun is level, the action is true, and then you check it all afterward freehand.

So the reticle can be plumb, but not plumb with the rifle's action at the same time?

Yea. I'm talking 99% long range here. You want the reticle level so set plumb line then set your scope level to agree. Doesn't matter if action is level as it has no bearing on the round in the chamber. Make sure your scope tracks true in vertical travel with no deviation and rlock on.

Absolutely, if I understand you correctly. The scope can easily rotated in the rings so the crosshairs are level (or plumb if referencing the scope’s Y axis) when the X axis of the barrel is far from it.

That was point made earlier, that Step 1 is to ensure the X axis of the barrel is true horizontal. Only after this has been done can other checks be made.

What if the reticle is misaligned in the scope tube?

Keep in mind most scope turrets aren't true level either as they typically float on an o ring for sealing purposes.

Like the precision in the scope base and rings, it’s an assumption that must be taken would be my answer.

If it's mis aligned you'll get a drift left or right when going up in elevation.

That’s where a true horizontal line or edge on a nearby surface becomes useful.

I hear you dee. I'm not arguing either. I've always wanted the reticle true to the receiver and bore so that when I dialed elevation I got an absolutely accurate movement from the reticle.

This is why I like and recommend the reticle-tru device. I've had a canted reticle from scopes straight out of the box.

Thinking about the geometry in what you describe, this would only be an issue if field adjustments are made to the scope for different shots, correct? Otherwise, once the Y axis crosshairs are plumb, the fact the scope body is slightly canted has no impact so long as the Y axis of the barrel is also plumb.

I guess theoretically that would be true TDan. The way I see it, it is fixing a mistake with another mistake but for a "set and forget" setup it should work.

Perhaps the key point to all of this is how some guys will adjust the crosshairs of their scope so they appear horizontal once the shoulder their rifle and look through the scope. Because most people cant or “tilt” their rifle when they shoulder it, they never realize the crosshairs were incorrectly adjusted to a rifle that wasn’t true horizontal at the time. I have seen this myself a time or two when someone checked out one of my rifles and claimed the crosshairs were “off” or not horizontal. Not wanting to start a needless debate, I offered no response.

Still, I suspect the level of canting the average person creates when shouldering a rifle creates less of a negative impact on the shot than other variables often at play. I offered the original post mostly for those who might wish to use their smartphone to perform a rough check of their current setup. However, it also created some very useful discussion.

I have always been of the opinion that what fits my eye is what I want whether it’s absolutely level or not. I have checked a few of my rifles and some are level and some are not (though all are close). I’m assuming the differences are the result of individual stock fit differences.

I don’t know if I am doing it right or wrong (I have read opinions going both ways), but that’s what I prefer so I’m not going to change. Since I am not a LR shooter I doubt it matters much, if at all.

I have one also, they work.