Definition: The motor power specification "50lbs" represents the maximum nominal force produced by the stepper motor alone.

The Nexus 6000 high pressure syringe pump's linear force specification is quoted at the pusher block meaning the system produces a real 450lbs with friction losses already netted out.  

Application: Actual pushing force is determined by a number of factors including the syringe diameter, the friction on syringes and the viscosity of fluids used. Metal syringes commonly require 20 lbs of force just to initiate movement.

Pressure limits of a syringe pump is calculated from the syringe ID. (pounds/square inch) Larger syringes have lower presser limits and smaller syringe have higher limits.