Oil pump binds or is it made to be that way

I have a question about the oil pump on a slant 6. With it off the motor and I am turning the shaft by turning the gear, should the turn stop at any time or should i be able to turn it freely and keep turning it? The one I have goes around almost all the way but then binds and stops. So apply more pressure and it turns more. Does that mean the shaft is bent?