it CAN use saiga magazines if you get the little adapter ramp, but I would suggest using the cheaper standard magazines instead and avoid drilling a hole in your trunion.
I just bought one of these and took it to the range and the trigger doesn't always reset. On my third shot the trigger was stuck back and when I looked at it I ND'd (thankfully) into the berm. The trigger got stuck a couple more times after that and I had to push it forward to get it to reset. Should I send it back to get fixed?