Here's my two cents worth.............. First and foremost I am not familiar with all of the machining practices or the quality control policies of "all" the manufactured rings. Nor...................do I believe that there are too many, if any, people reading this post who can say with any great certainty that they are familiar with machining or quality control policies of "all" scope ring manufacturers. I started lapping rings three or four years ago now, and once I started I recognized that there was a need for it. I have Ruger 77s and use Ruger 77 rings. Although they looked good with the ring alignment tool, the two pointed mandrels, when I tried lapping it was instantly noticed that the rings were (1) somewhat out of round, (2) out of alignment as well. I am sure that some will say that Ruger rings are junk to begin with, well I am not sure of that, only sure that the rings did need some attention. Logically speaking for me, it is impossible to machine a set of rings at a factory and then expect those rings to fit every application perfectly without any final assembly/fitting once they are placed on a scope base or scope mount of some kind. Honing/lapping with a mandrel is a good way to ensure alignment as well and roundness when fitting up rings. As for how much to lap, I use the black finish on the inside of the ring to determine "how much" to lap. I prefer to get at least 70% of the black finish on the inside of the ring to be removed before I stop lapping. If you are concerned about lapping "too" much material out of the ring, there's always the opportunity to remove the mating flat surfaces of the scope rings if that did happen. However...for me the likelihood/rick of lapping a ring too much is not too great. I have never "bedded" a scope ring, however I do see the benefits of bedding to ensure alignment of the scope to the scope rings to the scope base/s. Also since I have been lapping my scope rings, the scope marks on the outside surface of the scopes have disappeared. As for those who say that it is not necessary, there's one way to find out by trying to lap those scope rings that do not need lapping. If there is at least a 70%, aligned, lapped surface on the inside of the ring, "then" the lapping was/is not necessary.