Light Machinegun Bug?

[Nomad44]

Hi Fans. I've battled my way through this game to the Sveta-Ostrow level with nothing else but a pistol and a sniper rifle (in NORMAL mode, single player). At the start of this level I became an update for my LMG - 200 magazine. LMG?!?!?!?! What LMG??? I've pressed every button on my keyboard (Logitech G19) and in every combination but I cannot find an LMG. Now I'm stuck at the point where I have to take out the helicopter. My companion carries a rocket launcher on his back but he doesn't use it and I have no access to it. So, that's it. Am I doing something wrong or is this a bug? Can't find anything about this problem in forums.