OK, The metal "bracket thing" has to be drifted out of it's dovetail. You will first have to remove the magazine tube. The magazine tube pulls straight out, although it may be "tight." In the event there are burrs where the screws go thru the "bracket thingy" DO NOT TWIST the magazine tube or you'll get real ugly scratches on the tube.
Once you have removed the tube, the bracket may just push out (left to right). Then you can slide the fore end wood forward and it will drop off the barrel.
To re-assemble, wood first, then the bracket, then the tube, then the screws, etc.
Coffinmaker