Sean:
Try using a wood dowel (preferably square in cross-section, nearly the same width as the inside of the mag body, by about 1/2" in fore/aft length), to both compress the spring and follower initially, and to re-compress the spring for re-assembly. Insert this dowel into the rear portion of the mag body (aft of the feed lips) when re-installing the spring, and it will eliminate the capability of the spring from launching. Also, it makes it real easy to insert a rod through a witness hole just in front of the dowel.