Who had the heaviest U23B and the heaviest B23-7? And what weight "was" the heaviest?
TNT
TNT
According to the U23B roster in "Extra 2200 South" issue 75 (official date April-June 1982), U23B ranged in weight from 246,000 pounds (CMStP&P) to 277,000 pounds (C&O). Runners up for the maximum weight were Texas Utilities's single unit, at 275,000, and Monon's eight at 272,000, and second lightest were NdeM 9100-9113, at 250,000. Just over half the total number built were in the 260,000-266,000 pound range.
Somehow it isn't surprising that C&0 (who introduced the 2-6-6-6 Alleghany type in steam and whose successor CSX ordered super-heavyweight 432,000+ pound six-axle diesels in recent times) should have had the heaviest!
For B23-7, I don't know. The lightest were probably some Mexican units built with very small fuel tanks.