When Act 4-2 starts, turn around and stand next to the barricade. Then flip the lag switch or standby and take cover on the sand bags in front of you. Next hit the switch again and it will put you where you were standing in a crouch position. Procede to do a KFF(kung fu flip) over the barrier. Then go around the building to the left and there will be unlimited amounts of boomshot, tourqe bow, long shot rifle, and a working hammer of dawn.