What your talking about is a staggered feed action.
Do not bend the box, and be careful as you can break the tabs off of the action improperly removing the box. The way I do them is with the barrel, and recoil lug still on, I find something to fill the space between the magazine and the recoil lug, I then take a big screw driver and push against the magazine box, using the spacer for leverage. The box will come right out.