If that's the LMG system, there are patent drawings out there. In the LMG system, basically, there's a notch on the hammer and on the bolt carrier, such that the hammer holds the bolt carrier back when it's cocked.
As the trigger is pressed, a cam on the trigger acts on the leg of the auto sear, causing it to cam the hammer down slightly, releasing the bolt carrier, then slipping off the leg of the auto sear.
Bolt carrier flies forward, trigger is pressed, so the hammer is caught by auto sear instead of the trigger sear as normal.
Bolt carrier approaches battery and trips auto sear, releasing hammer to fly forward and strike the firing pin.
But, that doesn't look like the LMG system, nor does it look like the slam-fire open bolt firing port weapon (FPW) fire control group, so I think it might be the tactical innovations open-bolt system for their proprietary upper. If so, I'm not sure how that system works, since I've never seen or used one.