This gun paper model is the StA-52 (Assault Rifle), based on the video game Killzone. This papercraft is designed by PepMaster. The primary weapon of the Helghast armies is the StA-52 Assault Rifle or LAR manufactured by Stahl Arms. The StA-52, firing a 5.56 x 45 mm cartridge, seems to be more of a modular weapons system than a single weapon, since almost all of the Helghast weapons use a similar drum-style magazine design. It has a bullpup design with a drum-mag behind the handguard. It has iron-sights in Killzone 2, and is used by low ranked Helghast forces. The rifle seems to use a gas operated mechanism with a secondary tube running on top of the barrel for exhaust pumping much like a modern day rifle such as the AK or M-16. It fires more rapidly than the M82 Assault Rifle, but the iron-sights and poor range limit its usefulness at longer ranges; however, it is quite useful at short to mid-range.
In Killzone, the StA-52 had a secondary function which fired green colored shells. Each shot fires 8 buckshot balls capable of killing an enemy instantly at short range. The shots also maim enemies at mid range, but their efficiency is lost due to the shot's spread cone. It is Colonel Gregor Hakha's gun of choice. The rifle seems to have a collimating red dot sight much like a modern G-36, though the sight is never actually utilized in-game and is replaced by simple zooming of the screen.
Killzone is a series of first-person shooter and third-person shooter video games exclusively for Sony Computer Entertainment's (SCE) video game consoles. The series is developed by Guerilla Games, a subsidiary of SCE. Killlzone currently consists of four games spanning over the PlayStation 2, the PlayStation Portable, and the PlayStation 3. The series began on the PlayStation 2 in November 2004 with Killzone, and continued on the PlayStation Portable in October 2006 with Killzone: Liberation. The next installment was Killzone 2, released for the PlayStation 3 in February 2009. The most recent installment is Killzone 3, released in February 2011 also for the PlayStation 3. A fifth game is currently in development for the PlayStation Vita.
You can download this paper gun from here: Killzone - StA-52 Assault Rifle Free Paper Model Download [Box] [Gavitex]