Years ago a couple of friends of mine, one multi-black belt and another a Master class USPSA/IDPA shooter, and myself, were having a conversation where we were trying to analogize USPSA classes to martial arts belt ranks. We came to the conclusion that B class is equivalent to a first degree black belt, for the following reasons:
(1) In both cases, B class and first degree black belt, this is the first level at which you can honestly say you have a decent mastery of the involved discipline. I mean, you’re not setting the world on fire or anything, but you basically know what you’re doing.
(2) Also in both cases, this is the level of proficiency the average, dedicated practitioner can reach if they just stay at it long enough. You show up for martial arts class a couple times a week, practice at home occasionally, you do that long enough, eventually you’re going to be a black belt. You shoot matches several times a month, go to the range a few times a month, dry fire at home on a decent though not obsessive basis, eventually you’re going to be a B class shooter. (In both cases this assumes a normal level of hand/eye coordination and no mental and emotional problems that get in the way.)
(3) Finally in both cases, this is the level that most people will never go beyond. For a couple of reasons. In the first place, because this is the level at which they know they’ve achieved a decent skill level, most people at this point figure they’re done: “I got my black belt,” “I got my B card,” and they’re satisfied. For another, this is the level that, to drive beyond, requires a greater amount of time and dedication than most people are able or willing to put out.
In IDPA I would say this level comes around high Sharpshooter.