i have to replace the bottom bracket on my specialized hard rock sport.the spindle is 68x125mm.the closest length i can find is the shimano un53 68x127mm.can i use this bb? thanks.

Acording to Specialized the BBthe hardrock sport for '05 is a truvative 68mm X 113?
What year is yours, and do you know if your bike has square or splined BB?

the bike is about 6 years old and the shaft is square.the length of the spindle is 125mm. i am a machinist so i am pretty good at measuring stuff.

A couple of mm on the spindle length shouldn't matter at all.