On the Ishapore 2A's, it seems that that Ishapore did indeed change the steel for the 2A's. From 1950 to 1965 they used a weaker grade steel which couldn't handle proof loads so they went back to the original EN steel (EN19 maybe?) That's what I gather from reading old posts and other sources.

Apparently Lee Enfield's fail catastrophically by buckling the bolt body and unlocking the bolt head from the receiver ring. Case fragments are what injure the shooter, or so I've been told. Stretching of the right side sounds reasonable to expect. It would be interesting to see photo's of such failures.

I'm interested in the strength of No4's. One hears about some being strong enough for conversion to 7.62 and other not. I wonder where that came from? Another myth or were there really poorly heat treated No4's out there?

The Lee Enfield is not a bad design for a military rifle. It has its flaws to be sure. That safety catch on the side of the receiver leaves a lot to be desired. The original bolt mounted safety was fine. It can get bumped off but not easily while the later safety was almost guaranteed to get bumped off. Then there is the likely hood of an AD if the trigger is depressed and the bolt closed onto a round rapidly as what happens when a cartridge is in front of the extractor. Never do that! In any case, the firing pin rests on the primer in that condition. There is a temptation to load the rifle with striker down then pull it onto halfcock which locks the bolt and sear - a great way to carry a gun on the ready. Wrong!