Actually, there are two eras of Mauser metallurgy to worry about. Prior to WWII, springs and pins could be excessively brittle. After about 1942, I don’t trust the heat treating in the receiver or bolt. The slave labor in the Nazi war machine was either very sloppy about heat treating, or they were using defective heat treating as a lovely future “gift” to their Nazi hosts. I’ve seen some Mauser receivers be dead soft and some be so hard it is a wonder they didn’t shatter.
Same was true for their armor plate
Same was true for their armor plate
Germany ran out of manpower. Japan didn’t belong in WW-II in the first place, but Hitler had a dozen ways to win WW-II and two or three ways to lose it and found the two or three ways. Simplest path for him to win was not to invade Russia. Russians I’ve spoken with who were alive at the time have said the place would have fallen apart on its own in another four or five years and Germany could picked up the pieces for free. Not invading Russia would also have solved the manpower problem.