Not all vendors machine the ends the exact same way. If the overall length of the screw is 1120mm, the length of the threaded part should be around 1050mm. The end that has the two fixed bearings will loose about 60mm of thread and the end with the floating single bearing will loose about 10mm of thread. But again, it depend on who machined it.
If you are trying to figure out how much travel you will get out of a 16xx ball screw, a rough estimate would be to subtract 125mm from the total length of the screw. That allows for a loss of 75mm for the machined ends and a 50mm loss for the nut.