I mostly agree with Bob. However, some servos will not tolerate being forced. I have stripped the gears of a Hitec HS-85 trying to get it to move. I figured "well maybe a bit more force is all it needs". Wrong! That lesson cost me a new gearset and time to fiddle with installing it.

For most servos this is a non-issue. I've had no problem moving JR 8411's, 4721's, 537's, 517's, 507's, and 241's... or Hitech 81's, 225's, 425's, 605's, and 645MG's. Watch out for HS-85's though... great servos but try not to force them. These are just the servos that I have personal experience with.

Andy Steere
http://astro.umsystem.edu/andy/rc/