Rickervision has a couple of good videos on the DA50 lower assembly and shooting it for the first time (if the linked below don't work, just Google Rickervision DA50):
https://m.youtube.com/watch?v=th8hLQaNUMc
https://m.youtube.com/watch?v=8SZLCgoFlSc
His comments before he shoots it the first time still make me laugh...