dsaul, forgive me if I'm misunderstanding your reply, but I think this RD definitely does have a pivot spring. I can rotate the RD clockwise and it will rotate against what I would say is pretty moderate spring pressure. That pivot spring holds the RD against its B-screw pretty tightly. I do think the spring is so strong that the RD probably rarely swings during use. If that's what you meant, then I do agree.

The Shimano RDs I've used (including an older STX and a current model Acera on my hybrid) have what I'd call "light" pivot spring force, and the RD is able to swing back and forth (and probably does during use). In these cases, the B-screw is not setting a fixed reference resting position of the RD, but a specific preload on the spring.

Andy, the way you describe it makes sense to me. I agree that the "fixed" type (even though it can still physically swing back) is a little easier to set. Do you know if other RDs in SRAM's "X" family share this "fixed" type of B-screw adjustment?