Charles,
The later SR BB with the solid axle used the same alloy cups and 3/16" balls. These cups and bearings were retained for the early C-record BB. At some point Campy realized that big balls are better, when it comes to durability, and they changed the entire C-record BB to use 7/32" balls. I suppose this was as big as they could go while still using the alloy cup with steel insert, since that is bulkier than an all-steel construction.
FWIW, Campy also had an old all-steel (late 1960's?) Record BB that used 3/16" balls. I have a spindle that is marked (something like) "per sphere 3/16" " I recently determined that the old Record BB that uses 3/16" balls is not interchangeable with the later 3/16" SR / early C-rec stuff. The old Record BB used thin-walled cups and had wider spacing between the races on the axle.
Tom Dalton
Bethlehem, PA
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