when taking it output the action upside down in a padded vise or something secure. Get a flathead screwdriver and a hammer(

). Put the tip of the screwdriver on thefront end(toward barrel) of the magbox, right at the base where the tab is that fits in the slot in the action. Now, give the screwdriver a good whack on the handle end with the hammer(not enough to break it

). This will "shock" the magbox and let the tab jump out of the slot, which will allow you to remove the magbox from the action. (You may wanna use safety goggles cause sometimes the magbox goes flyin, depending on how hard you hit it).
when re-installing itWith the action in the same position, place the magbox so that the rear tab is in the slot. Now take the same screwdriver and place the tip right on the front tab( where it bends off the box), push down and in at a 45deg angle toward the magbox. While pressing down
firmly, give the handle of the screwdriver another whack with the hammer. This will again "shock' the magbox, and as long as you keep pushing down firmly, allow the magbox to snap into place.
This method shouldnt bend the magbox in any way( unless you really hit it hard

), and is actually really easy after you do it once.
Hope this helps,
Mike