I hate to show my age, but I will. Sometime in the distant past I saw an article printed either in a magazine or a gunsmithing book about safety breaching Mausers. The general idea was that you took the bolt and made it somewhat like a Remington 700 in the front of the lugs, and then recessed the bolt nose into the barrel. The idea was to give you something of an enclosed case head. My thought at the time was, Boy, I'd like to fiddle with that.
So now, my 70 plus years: I cannot remember where I saw it. It looked very clever when I saw it. I saw it probably back in the 70's. Anyone with better recall than I have?