The Assault rifle is a conventional weapon in Alan Wake's American Nightmare. It is unlocked after the player collects 20 manuscript pages. It can be found just before the powerhouse at the Drive-In Theater.
"A fully automatic is a great way to make things look like Swiss Cheese. Even the toughest enemies will feel like taking a little nap after you've emptied a full clip into them."
The Assault Rifle is one of two fully automatic two-handed weapons, the other being the combat shotgun. In-game, the Assault Rifle bears a resemblance to the real-world M16A1. The Assault Rifle features a 25 round magazine, a high rate of fire, and a medium reload speed. The Assault Rifle deals decent damage per shot allowing the damage per second stat of the weapon to be pretty good. Firing a full magazine into an enemy will usually prove fatal, except in the case of the Giants. The Assault Rifle is a solid choice for a two-handed weapon, but will probably have to be supported by a one-handed weapon as the high rate of fire will make for frequent reloads.
The Assault Rifle is first found in a weapon's case at the Drive-In just after passing through the car park and before reaching the power station (right after Mr. Scratch taunts you for the second time) and requires 20 manuscript pages to unlock.
M16 rifle on Wikipedia