More Generally: CI vs ABS
Maybe I can broaden my question, because I don't understand why the dims on CI and ABS are so different for the same sized pipe.
Below is a set of drawings taken from CharlottePipe.com showing dims for CI on the left and ABS on the right. Some points of note: the CI Short Sweep is larger than the ABS Long Sweep (compare CI-SS 'D' to ABS-LS 'B'); the CI 1/4 Bend is approximately the size of the ABS Long Sweep (compare CI-QB 'D' to ABS-LS 'B'); the ABS Combo is a much larger turn than the ABS Long Sweep (compare ABS-CB 'A' to ABS-LS 'A').
So, based on this it would seem fair for CI Short Sweep to be used in places that ABS Long Sweep can be used. For that matter, given the dims for CI Quarter Bend vs. ABS Long Sweep it'd seem like that could be used in the same places (as a practical point, not by code). So... what's going on here? Can someone explain the logic of all of this?