There are two wear points to consider here. Hinge wear & bolt wear. The Lefever mentioned has a ball screw hinge which can be adjusted for hinge wear. The Win 21 has replacable hinge rolls for hinge wear compensation.
On both the top lever will go left to compensate for bolt wear. If both Hinge & bolt wear are present the hinge should not be "Over Adjusted" to compensate for the bolt wear, the tapered bolt bites deeper to take care of that as the lever goes left.
The screw in the bottom of the 21s bolt notch is not for centering the lever, but to limit the depth the bolt can enter. The 21 has a very shallow angle to the bolt & if allowed to go home without the screw stopping it, it can stick bringing on hard opening & also increased wear to the bolt surfaces. As bolt wear occurs the screw should be turned "IN" slightly, just enough to compensate for the wear. This allows the bolt to bite a bit deeper to take up the wear & the lever will come left as a result.
Remember bolt wear normally occurs faster on a new gun than an older one as the mating parts wear-in to one another.
