I've been told by people who take old M-1 barrels and cut them up for other uses that M-1 barrels are 4140 steel. During WWII, was every M-1 barrel MPI'd and HPT'd?
I ask because I don't know. Given the production technology and production demands at the time, I suspect not. But it's possible. Since this point has now been brought up, it would be useful to know. Because if M-1 barrels were 4140 steel and not every barrel was MPI'd and/or HPT'd, I'm not sure why they'd be rugged enough to help win WWII and yet inadequate for civilian use.