Posted 15 December 2011 - 08:56 AM
funny you should ask this, I just had exactly the same problem with an SR3 mag I was servicing today.
The roller spindle is sort of press fitted into the arm, so you can't actually stop it spinning if it's come a bit loose, at least not without removing the arm and trying to clamp the bottom of the spindle, or re-securing the press fit somehow.
But the force required to turn the spindle should still be strong, it's just that the force needed to undo the screw is greater. So the easiest solution is to try and reduce the screw binding friction. I got mine out by soaking the screw head in a rust penetrant/lubricant spray called CRC 2-26, something like WD-40. Then give the screw a short sharp twist with a screwdriver.
If that doesn't work try applying a little heat to the screw head with a soldering iron before trying again.