Here is a Free weapons pack that has been in circulation for sometime and proven pretty popular.
This pack contains a verity modern weapons for your games/media productions. Avarage polycount is at 1200 polys. Textures are 512x512.
This pack contains the following weapons:-
* FN2000 W/ Grenade launcher
* Styre-Aug Green
* Styre-Aug Black
* Styre-Aug W/ Scope and Flashlight
* M16 W/ Grenade launcher
* MP5 Sniper scope and silencer
* MP5 W/ Front grip
* MP5 W/ Alternative Stock
UW Mapping & Texturing: John "Bronco" Hedges
Modeling: Nermin "Maximo" Bajagilovic