Why I appreciate the Lee Enfield.

[Surpmil]

Surpmil,

That is a very good picture of what happens after a few reloads. (if full length re-sized,... or used in a rifle with a generous chamber,... or plain overused brass...)
I have had them blackened all the way around where they came apart. We can normally see a light coloured ring around the case where they are about to come apart, and the next reload will more or less guarantee this.

I too would like an explanation of what happened when the shooters got their glasses broken, mentioned by Lee Enfield in a previous post. I see no reason for it, unless as Sentryduty mentions above, it had something to do with "body positioning".
I can well imagine a "stock crawler" whipping the bolt back into his glasses whilst engaged in 'rapid fire', but if the striker blew back, they would be fishing more than glass out of the chaps eye.

A chamber cast would be an option to see if there is a contributory defect there.

Agree that the "glasses broken by firing pin" is a hard one to explain except by a broken firing pin, but as you say, that should lead to more than broken glasses in the case of serious case failure. A long neck and a short butt?! Hard to say what broke the glasses unless there is an obvious mark from the impact on the cocking piece. A person not overly familiar with the rifle or who did not examine the bolt closely might not notice a broken firing pin, and if the tip was jammed in the bolt head that might cause a premature ignition and case failure? If it did, the broken tip and perhaps collar being driven back would allow more gas than usual down the firing pin hole? An oversize firing pin hole in the bolthead might be a contributory factor in such a case too?