DougW,
Right calculation, wrong units.
When the area is expressed in Kcmils, and the length is expressed in _1000 feet_, K for copper is something like 10 or 12 (depends on temperature and the reference that you are looking at). I'll trust you that the K for steel is 100; for iron it is about 50, but for different steels it can be all over the place.
Area in circular mils is the diameter in mils _squared_.
So we get:
area = 250^2 = 62.5Kcmil
length= 4 inches /12000 inches = 3.3333*10^-4 Kfeet
resistance = 100 * 3.3333*10^-4 / 62.5 = 0.5 milliohm
-Jon
