Well well! Is it possible the Indians were using a stronger than original spec steel already so no changes were needed? On the internet we find circular references with no reference source so it could be hearsay/myth that's been quoted as fact as you say. There is that niggling thing my uncle told me about the 308 modified No1 that set the bolt back (not a quick process but how many shots it took I don't know - I don't think he knew). Well, there must be a way of finding out for sure.

My understanding (which is open to correction) is that proof loads were 25% above normal and three such loads should not set the bolt back measurably. That would be a little above 7.62 NATO loadings but how many shots would a rifle operating close to its strength limit withstand? I don't know. It is said the No4 is a stronger action - strong enough to handle 7.62 NATO but with a smaller safety margin than a purpose built 7.62 NATO.

We know what the original steel specification for No1's and that strength is known as is the 4140 used in No4's so we have some sort of comparison. I don't know so I can't do the comparison.

In the meantime I'm going to erase what I thought was fact until proven otherwise.