Proprietary was probably a bad choice of words on my part but he's the only guy I know of doing it to Mini 14's.
What he does is drill holes in the bottom of the action and in the rifle stock. Then metal pins are affixed in the stock. I imagine it's a 2 part epoxy but I don't know exactly what he uses. When the action goes in the stock the affixed stock pins slide in the new holes in the action holding it firmly in place. The back right pin has a hole drilled in it and is threaded to accept a screw. The charging race way is drilled so this screw sets flush in the race way.
Does sound anything like the way it's done on a M14? If so it kinda makes sense where idea came from. That's about as well as I can describe it on a smart phone. I'll be back in town Saturday and will pop it out of stock and snap a few pics if you'd like to see it.
