Quote: "Not to worry, i found the arms model. Now, just got to work out what all these boxes are for? "
Those boxes represent bones or dummy objects used to drive the animation of the gun. Having the gun parts skinned to the bones this way allows the entire arm/weapon rig to render quickly in a single pass.
Some of the boxes are used to represent other things as well:
-smoke and muzzle flash locations
-non-rendering auxiliary bones used to drive additional procedural animation (like look-at constraints, spring controllers, or IK-switchers).
