Title nearly says it all. I noticed that, when I am at 0 bullets with the Raid LMG and use a heavy synthesis, that the LMG will not reload itself, until I switched to the weapon to start the reload sequence. I can cancel the animation and switch back to another weapon afterwards however, and the LMG will reload itself after a given time. I think that this is a bug. If it's an intended mechanic, the perk description definitely doesn't imply this reaction in any way at all.