That's what I was thinking 427. Maybe a hybrid FCG between AR/AK. I was trying to think about the wings on the AK hammer that the trigger hooks onto. It would be simple if there was enough width in the AR bolt carrier slot for the AK hammer to swing through it's full arc and hit the firing pin, but I don't think it's wide enough. Of course I'm at work without the parts in front of me to measure. Maybe use a PSL style hammer with the single wing, and offset the trigger just a little so that there is room for the one left wing to arc up through the carrier slot?