I have an EXP in a drawer about 10' from me, along with other devices which I believe cover pretty much everything mentioned here. I couldn't suggest that any are bad toys.
What I will suggest is that we lose sight(literally) of what we're doing.
Where each component is made well & square, guns are not built square, they're built to best fit with these components. That's close enough.
Why is close enough good enough? Because very little has to be square, or level, to work for us.
Important is only what we can repeatedly establish from shot to shot, one condition to the next.
If your shouldering consistently cants the gun 3degs(whether you know it or not), and you've zero'd and load developed with this, and it's how you'll be shooting in the field(or want to), then all that matters is your establishing of this as prerequisite to each shot. The gun overall, including individual components, could be canted, rotated, tilted, skewed, bent, etc., and it doesn't matter one bit provided the point of aim(POA) is taken back to your reference.
Individual components also includes the scope body and it's internals.
So forget the gun for a minute, assuming that as long as your not pointed at the guy next bench over, you're ok there. How do we establish our reference POA, while dialing, or holding over?
Now we're back to reticle level.
Lotta reticles out there. Some are dots which we're not gonna level. Some reticles(well, many) are not mounted square to internals, and we should not twist our guns around them anymore than all the other gun components.
But we can level our elevation adjustment, and hope this will cause plumb horizontal stadia(if needed). 'Level' here is 'plumb',, that's a reference, given that gravity is our reference, which bullet drop is tied to.
We can level our visible elevation hold-off, just the same, for the same reasons.
Can't usually do both. Choose one or the other.
So we can dismiss the gun build, and most of the scope, and most level toys, and set a plumb POA as our reference. Then, we can tweak this POA for external ballistics we can't compensate for on a bench(like spin drift & muzzle whip). Things we have to shoot(at distance) to adjust for.
We can dial lines, and shoot lines. While you're at it, measure actual click values, box test your adjustments, learn what you can about your high dollar scope, and ballistic software.
So where should we put the final reference? Where should we mount it?
I like the scope itself, as this reference can then follow that scope from gun to gun. In fact, I can store that scope in a safe, and it forever holds it's reference. I can put in on another gun & go shooting to mid distances & group shooting at least(tweak it later). It's potential madness reduced to stick figure solution:
Scoplevel Anti Cant Leveling Device
Would I like for this plastic *** to be CNC machined in exotic metal? NO! In the field, 'nice' would be damaged or damage my scope. But with decades of use, and occasional whacking of these things, no ScopLevel has ever let me down. You can twist it, springs right back.
You could mount a really 'nice' level anywhere else, but it better be fully coarse/fine adjustable from there, or it will never be right.
The other attribute I like about ScopLevel is that it's squarely visible, with my shooting eye, while I'm pulling the trigger. Off hand, I cannot think of any other that is(but I'm sure there is).
Anyway, think about what we're doing, and consider how you can cover exactly that.
