Better'n the funny papers!
What's funny is the inability of this esteemed crowd to understand the dynamics at play. Saw the Wheeler Engineering gizmo on the Brownells page today; guess it is the one Alex referred to? How many tools do you need to own to replace the 74-3333 boresighter with collimation grid? Evidently several. Got to have a level and a crosshair to align your reticle with. Does the barrel actually have to be "level"? Not really. Can a tapered barrel be "leveled" without a shim? Not really. Can a cross-bolted fastener on a tapered barrel be leveled without a shim or dual independent floating fasteners? Not really
But, it don't matter! You're looking for bore concentricity not scope to barrel level. Seems there might be a grid in the Wheeler gizmo, if not; suggest one as an upgrade. Of course, the complexity of the fastener mechanism and the independence of the leveling system are merely much greater complexities than necessary; but to the anal-retentive crowd that's a good thang! How's the barrel leveling tool work with a canted scope base or ring set? Don't matter, does it? There's no elevation gain if it's all level.
If we understand that mechanical systems, cannot be made "perfect"; how can we fail to grasp backlash and tension relief? There are no electronic sights of a telescopic nature which employ a non-holographic reticle. Is one such sight what the perfection crowd will have to embrace? Seemingly, but it will have drawbacks of its own, for man cannot make perfection.
With all the uncontrollable variables that effect bullet flight, I find it ludicrous to expect mechanical perfection when most users have no idea how to even approach it. If you don't know to relieve backlash; what else don't you know? Most don't even know to buy their own finish reamers for the "custom builds" they fund. What most shooters "know" these days is how to authorize a website purchase, and that if they spend XXX many dollars, they should get "quality" results. Of course that depends on who did the building, who made the ammo, and who's doing the shooting...
How many have ever measured their scope base for mount concentricity, or even thought it could be out? Lots of them are...
There are so many variables that must be controlled and understood to achieve routine precision and "accuracy" with the rifle, that in terms of commonality and most versatility, I have found the most essential tool to own, if utilizing telescopic sights, is the barrel spud mounted boresighter with integral-etched reference grid. The Bushnell 74-3333 has served me well. If one wishes to adapt it to external mount rather than spud use, it should be easily accomplished.
Regarding the dual pic-rail "scope checker" which appears to mount on another picatinny or weaver rail, it seems to create more questions than it solves.