From comments here comes a link to the patent on the firing mechanism of the Volunteer Enterprise Commando rifle.
UPDATE: If you need gunsmithing work on a Commando, talk to Knoxville-based Coal Creek Armory. I’ve talked to the head of the company. He owns a number of them and their gunsmiths have fixed up quite a few. They’ve had success in including fabricating new firing pins, which seems to be one of the more common parts to break.