Before installing this, take your version of the M16 from these links:

http://www.gta4-mods.com/weapons/m16a4-f14904
http://www.gta4-mods.com/weapons/push-m16-a2-f15680
http://www.gta4-mods.com/weapons/m16-a4-with-acog-and-grenade-launcher-f10220