I've looked for an answer to this, but I haven't been able to find one. I'm familiar with Shimano RDs -- the B-screw sets the preload of the RD body spring, but the RD body is still free to rotate about its mount until it physically hits the chainstay counterclockwise or runs out of chain slack clockwise. The B-screw maintains contact with the hanger when rotating the RD in either direction.

I recently bought my wife a used 2007 model Trek and it has a SRAM 3.0 RD (entry level hybrid type bike). I gather this RD is equivalent to SRAM's X3 today. On this model, the body spring seems MUCH stronger than the Shimano springs with which I'm familiar, and the B-screw on the SRAM seems to be more of a travel limit screw than a spring tension screw. I can rotate the SRAM RD clockwise (which lifts the B-screw off the hanger), but, when the RD is at its resting position with the B-screw against the hanger, I cannot physically rotate it further counterclockwise.

Am I understanding that functional difference correctly and, if so, is this functional difference consistent throughout the SRAM line? Do all SRAMs use the B-screw as a travel limiter rather than a body spring preload, or is that perhaps the case only with this entry level 3.0/X3 RD?