Go to the Easton area in Algonquin. At the Grand Easton Terminal, go up the stairs in front. Keep going around that floor until you see a small pond. Move past it until you see a turn going left. Go to the left to get in between a tall building and a smaller one. At the end of the passageway is a dead end. Turn and you will see a glowing orange garbage can. Behind it is an M-4 assault rifle.